Brain Grain · braingrain.in
Botany — Practice Paper · Set 1
Class: 11Samacheer KalviMax Marks: 93
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.The female sex organ of red algae is known as a. Archegonium b. Spermatogonium c. Carpogonium d. Oogonium[1]
2.A major site for the synthesis of lipids ……………. (2013 NEET)(a) Rough ER(b) smooth ER(c) Centriole(d) Lysosome[1]
3.Stele include a) Endodermis, pericycle, & Vascular bundle b) Pericycle, Vascular bundle & pith c) Cortex, endodermis, & Percycle d) Xylem, phloem, cambium, & Pith[1]
4.The numbers of known species of Angiosperms in the world is a. 268600 b. 286600 c. 224400 d. 274832[1]
5.I) Phellogen – A. Cork II) Phelloderm – B. Cork cambium III) Phellem – C. Lack suberin IV) Phelloids – D. Secondary cortex[1]
6.The bioassay of ABA was done with a) Rice b) Wheat c) Maize d) Barley[1]
7.When a plant is wounded, the wound is healed by the formation of new cells, by the cavity of a) Primary meristem b) Apical meristem c) Secondary meristem d) Intercalary meristem[1]
8.Proteins perform many physiological functions, for example, some functions as enzymes one of the following represents an additional function that some proteins discharge a. Antibiotics b. Pigment conferring colour to skin c. Pigments making colours of flowers d. Hormones[1]
9.Products of light reaction in photosynthesis are a) ATP & NADPH 2 b) ADP & glucose c) Ferredoxin and cytochrome b6 d) Cytochrome[1]
10.In apple and plum, the method of breaking seed dormancy involves the process of:(a) impaction(b) Scarification(c) exposing to red light(d) Stratification[1]
11.Skeletal elements are a) Carbon, Hydrogen, and Oxygen b) Nitrogen, Phosphorus, and Calcium c) Potassium, Magnesium, and Sulphur d) Nitrogen, Sulphur and Phosphorus[1]
12.The theory equivalent to Tunicia Corpus theory is a) Histogen theory b) Korperkappe theory c) Apical cell theory d) Quiescent center concept[1]
13.The most widely occurring Cytokinin in plants is a) Indole Acetic Acid (LAA) b) Indole Butyric Acid (IBA) c) Pentenyl Adenine (IPA) d) Naphthalene Acetic Acid (NAA)[1]
14.Carpels are obliquely placed in the family a) Fabaceae b) Solanaceae C) Liliaceae d) Malvaceae[1]
15.End products of fermentation in yeast is:(a) pyruvic acid and CO 2(b) lactic acid and CO 2(c) ethyl alcohol and CO 2(d) mixed acid and CO 2[1]
Part II — Short Answer Questions 14 × 2 = 28
Answer briefly. (Answer all questions.)
16.(i) The evolution & classification of flowering plants – Arthur cronquist (ii) Origin of species – Engler & prantl (iii) Philosophia botanica – Linnaeus (iv) Theorie elementaire de-botanique – A.P. de. Candolle[2]
17.Mention any two industrial uses of alcoholic fermentation.[2]
18.Name 4 common basidiomycetes[2]
19.Who said that different kinds of plastids can transform into one another?[2]
20.Which one is wrongly matched Column I Column II A. NADH +H + Three ATP B. Glycolysis Twenty four ATP C. FAD Two ATP D. Cytoplasmic NADH+H + Two ATP[2]
21.(i) Toad stools are known as an edible mushroom (ii) Volvariella volvaceae and Agaricus bisporous are known for their high poisonous nature (iii) Claviceps purpurea produces ergot-used as vasoconstrictor (iv) Aspergillus flavus infest dried foods and produce carcinogenic toxin called -aflatoxin[2]
22.(i) Chara thallus is encrusted with calcium carbonate (ii) Siliceous wall occurs in the cell wall of Diatom (iii) Soil inhabiting algae – Fritshchiella (iv) Cladophora crispate is growing now[2]
23.(I) The chromosome does not divide as chromatids, for centromere does not divide – Anaphase I (II) The chromatids move to the opposite poles by the splitting of the centromere – Anaphase (III) Sister chromatids get separated by splitting of Centromere – Anaphase II (IV) Homologous chromosomes appear as bivalent or tetrad – Metaphase II[2]
24.Identify the diagram and label the parts.[2]
25.Draw the structure of TMV and label the parts and explain in a word or two[2]
26.The given diagram is verticillaster[2]
27.How Cronquist classified the angiosperms?[2]
28.Identify the correctly matched pair a. Actinomycete – a) Late blight b. Mycoplasma – b) lumpy jaw c. Bacteria – c) crown gall d. Fungi – d) sandal spike[2]
29.Biosystematics Define & Give its objectives.[2]
Part III — Long Answer Questions 10 × 5 = 50
Answer in detail. (Answer all questions.)
30.Distinguish between Eustele and Atactostele[5]
31.Korper Kappe theory:[5]
32.Describe the steps involved in cytological techniques.[5]
33.Define Senescence.[5]
34.Do you have an R.O. Purifier ¡n your house? Explain the principle behind it.[5]
35.Differences between Sapwood (alburnum) and Heart Wood (duramen)[5]
36.Compare sympodial branching with monopodial branching.[5]
37.Notes on Medulla or Pith.[5]
38.Mention the role of NADH dehydrogenase enzyme in the electron transport system.[5]
39.Why plants transport sugars as sucrose and not as starch or Monosaccharide (Glucose & Fructose)[5]
🔑 Show Answer Key — Set 1
- 1. c. Carpogonium
- 2. (b) smooth ER
- 3. b. Pericycle, Vascular bundle & Pith
- 4. a. 268600
- 5. a) B-D- A-C
- 6. a) Rice
- 7. c) Secondary meristem
- 8. d.Hormones
- 9. a) ATP & NADPH 2
- 10. (d) Stratification
- 11. a) Carbon, Hydrogen, and Oxygen
- 12. b. Korper Kappe theory
- 13. c) Pentenyl Adenine (IPA)
- 14. b) Solanaceae
- 15. (c) ethyl alcohol and CO 2
- 16. The correct evaluation of these statements is: (i) The evolution and classification of flowering plants by Arthur Cronquist is True, as Cronquist developed an important system for flowering plant classification. (ii) Origin of Species by Engler and Prantl is False, as this work was authored by Charles Darwin, not Engler and Prantl. (iii) Philosophia Botanica by Linnaeus is True, as Linnaeus published this foundational botanical work. (iv) Theorie Elementaire de Botanique by A.P. de Candolle is True, as de Candolle authored this important botanical treatise. The answer is: True, False, True, True.
- 17. Two significant industrial uses of alcoholic fermentation are found in the food and beverage industries. In bakeries, alcoholic fermentation, primarily carried out by yeast (Saccharomyces cerevisiae), is crucial for preparing various baked goods such as bread, cakes, and biscuits. The yeast ferments sugars in the dough, producing ethanol and carbon dioxide. The carbon dioxide gas gets trapped in the dough, causing it to rise and giving baked products their characteristic light and airy texture. The ethanol evaporates during baking. Secondly, in beverage industries, alcoholic fermentation is fundamental for the production of a wide range of alcoholic drinks, including wine, beer, and spiri…
- 18. Puffballs, Toadstools, Birds nest’s fungi, Bracket fungi, Smuts Rusts, Smuts.
- 19. A. F. W. Schimper proposed the theory that the three different kinds of plastids—chloroplasts, chromoplasts, and leucoplasts—can transform into one another according to the physiological needs and demands of the plant body. This concept is known as the plastid interconversion theory. Schimper demonstrated that these plastids are not fixed in their form and function but can undergo reversible transformations. For example, chloroplasts can be converted into chromoplasts during fruit ripening when the green color changes to yellow, orange, or red due to the breakdown of chlorophyll and accumulation of carotenoid pigments. Similarly, leucoplasts can develop into chloroplasts when exposed to l…
- 20. The statement that is wrongly matched in the given options is B. Glycolysis – Twenty four ATP. Let's analyze each option for accuracy regarding ATP production in cellular respiration. NADH + H+ typically yields 3 ATP molecules when its electrons are passed through the electron transport chain in aerobic respiration. FAD, specifically FADH2, yields 2 ATP molecules through the electron transport chain. Cytoplasmic NADH + H+ can yield 2 ATP molecules, particularly when its electrons are transferred into the mitochondria via specific shuttle systems, such as the glycerol phosphate shuttle. However, glycolysis itself, the initial stage of glucose breakdown, produces a net of 2 ATP molecules di…
- 21. Evaluating each statement: (i) Toadstools are actually poisonous or inedible mushrooms, not edible ones, making this False. (ii) Volvariella volvaceae and Agaricus bisporus are edible and cultivated mushrooms, not poisonous, making this False. (iii) Claviceps purpurea produces ergot, which contains ergotamine alkaloids used as a vasoconstrictor in medical applications, making this True. (iv) Aspergillus flavus infests dried foods and produces aflatoxin, a carcinogenic mycotoxin, making this True. The correct answer is False, False, True, True.
- 22. The correct answer is c: (I) True (II) True (III) False (IV) True. Statement (i) is true because Chara thallus is indeed encrusted with calcium carbonate, which gives it a characteristic gritty texture. Statement (ii) is true because diatoms have siliceous cell walls composed of silica, which forms their distinctive glass-like frustules. Statement (iii) is false because Fritschella is not a soil-inhabiting alga; it is actually an aquatic alga. Soil-inhabiting algae include forms like Chlorella and Scenedesmus. Statement (iv) is true because Cladophora crispata is a green alga that is currently growing and found in various aquatic environments.
- 23. The correct answer is (IV) Homologous chromosomes appear as bivalent or tetrad – Metaphase II. However, this statement requires clarification. During metaphase II, individual chromosomes (each consisting of two sister chromatids) line up at the metaphase plate, not bivalents. Bivalents or tetrads appear during metaphase I when homologous chromosomes are paired together. The correct statement should be that homologous chromosomes appear as bivalents or tetrads during metaphase I, not metaphase II. Statement (I) is correct for anaphase I, where chromosomes do not divide at the centromere because homologous chromosomes separate as whole units. Statement (II) is correct for anaphase of mitosi…
- 24. This diagram illustrates a dark field microscope, which is a specialized type of light microscope used to enhance the contrast in unstained samples. The labels indicate its key components: A represents the objective lens, which gathers light from the specimen and forms the primary image. B points to the stage, where the specimen slide is placed for observation. C indicates the condenser lens, responsible for focusing light onto the specimen. D denotes the patch stop, a crucial component in dark field microscopy that blocks the central light rays, allowing only scattered light from the specimen to reach the objective lens. E identifies the light source, which provides illumination for view…
- 25. The structure of Tobacco Mosaic Virus (TMV) consists of three main components: the nucleic acid, which is single-stranded RNA (ssRNA) forming the genetic material at the core; capsomeres, which are individual protein subunits that form the protective coat; and the capsid, which is the complete protein coat or shell composed of multiple capsomeres arranged in a helical pattern around the RNA core. The capsid provides protection to the genetic material and determines the overall helical shape characteristic of TMV.
- 26. The given diagram represents a verticillaster inflorescence. In this type of inflorescence, the A denotes the central axis. The B points to the monochasial scorpioid lateral branches, which arise in the axils of opposite leaves and form dense clusters of flowers at each node. The C indicates the older flowers, which are typically located towards the base of these lateral branches, as the flowering proceeds acropetally within each cyme but appears whorled due to the condensed internodes. This type of inflorescence is characteristic of plants belonging to the Lamiaceae family, such as mint.
- 27. Cronquist classified the angiosperms into two main classes: Magnoliopsida and Liliopsida. Magnoliopsida, commonly referred to as dicotyledons or dicots, includes flowering plants with two cotyledons, typically exhibiting net-like venation in leaves, and possessing flower parts in multiples of four or five. Liliopsida, commonly referred to as monocotyledons or monocots, includes flowering plants with a single cotyledon, typically exhibiting parallel venation in leaves, and possessing flower parts in multiples of three. This classification system was based on morphological characteristics and represented a significant approach to angiosperm taxonomy.
- 28. The correctly matched pair is: a. Actinomycete – lumpy jaw, b. Mycoplasma – sandal spike, c. Bacteria – crown gall, d. Fungi – late blight. Lumpy jaw is a disease of cattle caused by Actinomycetes. Sandal spike disease affecting sandalwood trees is caused by Mycoplasma. Crown gall, a plant disease characterized by tumor-like growths, is caused by the bacterium Agrobacterium tumefaciens. Late blight of potato is a fungal disease caused by Phytophthora infestans.
- 29. Biosystematics is the science that combines cytological, genetic, and ecological approaches to study the relationships and evolution of organisms, particularly focusing on speciation and population dynamics. The main objectives of biosystematics are to understand the genetic basis of variation within and between populations, to determine the mechanisms of speciation and evolution, to clarify the relationships between closely related species, to study the role of chromosomal changes in evolution, and to integrate molecular, genetic, and ecological data to provide a comprehensive understanding of organism classification and evolutionary relationships.
- 30. Eustele and Atactostele are two different patterns of vascular bundle arrangement in plant stems. In the Eustele condition, the vascular bundles are arranged in the form of a ring or cylinder around the central pith region. This organized arrangement is characteristic of dicot stems, such as in sunflower plants, where the bundles are clearly defined and regularly positioned. In contrast, the Atactostele condition is characterized by vascular bundles that are scattered irregularly throughout the ground tissue without any definite pattern or arrangement. This scattered distribution is typical of monocot stems, such as in maize plants, where numerous small vascular bundles are distributed th…
- 31. Schuepp (1917)- proposed it According to it, Root system has 2 zones – Korper and Kappe Korper – zone forms body and Kappe forms the cap This theory is comparable to Tunica – corpus theory of shoot apex.
- 32. There are different types of mounting based on the portion of a specimen to be observed. * Whole-mount: The whole organism or smaller structure is mounted over a slide and observed. * Squash: This is a preparation where the material to be observed is crushed/squashed onto a slide so as to reveal its contents. Example: Pollen grains, mitosis, and meiosis in root tips and flower buds to observe chromosomes. * Smears: Here the specimen is in the fluid (blood and microbial cultures etc) are scraped, brushed, or aspirated from the surface of the organ. Example: Epithelial cells. * Sections: Freehand sections from a specimen and thin sections are selected, stained, and mounted on a slide. Examp…
- 33. Ageing or getting old is called senescence. It refers to all collective, progressive and deteriorative processes which ultimately lead to complete loss of organization and function (Eg. leaves turn yellow and fall off from plant).
- 34. Yes / No – R.O. is working on the principle of osmosis. but in the reverse direction. In regular osmosis water moves from its higher concentration to its lower concentration through the selectively permeable membrane but here water moves from lower concentration to higher concentration through selectively permeable membrane. Since against concentration gradient, there is the expenditure of energy, to apply pressure, to force water in a reverse direction. Eg- Desalination plants to purify seawater also work like R-O-Purifiers Movement of Water in house hold usage.
- 35. Sapwood and heartwood are two distinct regions of secondary xylem that differ in their physiological state, location, appearance, and functional properties. Sapwood, also called alburnum, is the living part of the wood located on the outer side of the secondary xylem. It is lighter in color and relatively soft in nature compared to heartwood. The cells of sapwood remain living and actively participate in the transport of water and minerals from the roots to the leaves through the xylem vessels. Sapwood contains no tyloses, which are balloon-like outgrowths of parenchyma cells that block the xylem vessels. Because the cells are living and the vessels are open, sapwood is not durable and is…
- 36. Sympodial and monopodial branching represent two distinct patterns of plant growth and branching. In sympodial branching, the growth is determinate, meaning the terminal bud ceases to grow and further growth is continued by lateral buds that arise below the terminal bud. This results in a zigzag pattern of growth, and the main axis is not a true continuation of the primary stem. Examples include Cycas. In monopodial branching, the growth is indeterminate, with the terminal bud growing continuously and uninterrupted, producing several lateral branches along its length. The main axis represents a true continuation of the primary stem, creating a more pyramidal or conical plant form. Example…
- 37. In the Dicot stem, Dicot root and Monocot root the central part is made up of ground tissue known as pith. Usually, starch, fatty substances, tannin, phenol, calcium oxalate crystals are stored in the pith. Function: storage
- 38. NADH dehydrogenase, also known as Complex I of the electron transport chain, plays a crucial role in initiating the transfer of electrons from NADH to the electron transport system. This enzyme complex contains a flavoprotein cofactor called flavin mononucleotide (FMN) and is associated with non-heme iron-sulfur proteins (Fe-S clusters). The primary function of NADH dehydrogenase is to accept electrons and protons from mitochondrial NADH that is generated in the matrix during the citric acid cycle and glycolysis. These electrons are then passed through the FMN and iron-sulfur clusters to ubiquinone (UQ), also known as coenzyme Q, which is a lipid-soluble electron carrier embedded in the i…
- 39. Plants transport sugars primarily as sucrose rather than starch or monosaccharides due to several important advantages. Starch is a polysaccharide and non-reducing sugar that is insoluble in water, making it impossible to transport through the phloem. Glucose and fructose are monosaccharides and reducing sugars that are soluble in water but are less efficient for energy storage and are highly reactive, making them unsuitable for long-distance transport. Sucrose, a disaccharide and non-reducing sugar, possesses ideal properties for transport. It is soluble in water even at high concentrations without increasing viscosity significantly, which allows efficient movement through phloem tissues…
Brain Grain · braingrain.in
Botany — Practice Paper · Set 2
Class: 11Samacheer KalviMax Marks: 93
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.I) Leaves – A) Antitransport II) Seed – B) Transpiration III) Roots – C) Negative osmotic potential IV) Aspirin – D) Imbibition V) Plasmolyced cell – E. Absorption[1]
2.From sieve elements sucrose is translocated into sink organs such as root, tubers etc and this process is termed as:(a) Xylem unloading(b) Xylem uploading(c) Phloem unloading(d) Phloem uploading[1]
3.…………… are the tools for identifying unfamiliar plants.(a) Flora(b) Keys(c) Monograph(d) Catalogues[1]
4.Phytochrome is a) Reddish phytohormone b) Bluish biliprotein pigment c) Photoreceptor of apical bud d) Unstable pigment molecule[1]
5.A quantosome is present in ……………. (JIPMER 2012)(a) Mitochondria(b) Chloroplast(c) Golgi bodies(d) ER[1]
6.Rubber is obtained from:(a) Bombax mori(b) Hevea brasiliensis(c) Quercus suber(d) Morus rubra[1]
7.The colourless cell in Nostoc in the intercalary position is responsible for nitrogen fixation is a. Holoblast b. Heterozygote c. Homocyst d. Heterocyst[1]
8.The taxonomy which involves the similarities and dissimilarities among the immune system of different taxa is termed as a) Chemotaxonomy b) Molecular systematics c) Sero taxonomy d) Numerical taxonomy[1]
9.Scientists, those who are connected with Ethylene (I) Denny (II) R. Gane (III) Kurosawa (IV) Cocken Options: a) (I) (II) & (III) b) (II) (III) & (IV) c) (I) (II) & (IV) d) (I) (III) & (IV)[1]
10.Onion lettuce, fennel, radish, cabbage are examples of a. perennial b. annual. c. centennial d. biennial[1]
11.The organism that is reproductively sterile is a. Wasp b. Worker bees c. Housefly d. Drosophila[1]
12.Kreb’s cycle is a:(a) catabolic pathway(b) anabolic pathway(c) amphibolic pathway(d) hydrolytic pathway[1]
13.The number of chromosomes in the onion cell is …………….(a) 8(b) 16(c) 32(d) 64[1]
14.Phosphate forming linkage with sugar is known as a. diester linkage b. peptide linkage c. phosphodiester linkage d. Ionic linkage[1]
15.Who established the structure of gibberellic acid?(a) Brain etal(b) Kurosawa(c) Cross et al(d) Yabuta and Sumiki[1]
Part II — Short Answer Questions 14 × 2 = 28
Answer briefly. (Answer all questions.)
16.Differentiate Homoiomerous and Heteromerous lichens.[2]
17.What are enzymes involved in phosphorylation and dephosphorylation reactions in EMP pathway?[2]
18.Mention the two Lateral meristems responsible for secondary growth.[2]
19.Assetion (A): Non cyclic photo phosphorylation occurs in the stroma of chloroplasts Reason (R): There is a continuous flow of electrons in this process.[2]
20.Give examples for Nitrogen Fixation with out nodulation.[2]
21.Explain different type of fleshy fruit with suitable example[2]
22.Name 3 Dermatophytes[2]
23.Organisms like Pseudomonas and Thiobacillus are of great significance in nitrogen cycle. How?[2]
24.Zygotene – Chromosomes appear as tetrads Pachytene – Synapsis of homologous chromosomes occur Diplotene – Condensation of chromosomes takes place Diakinesis – Terminalisation of chiasmata occur & Nucleolus Disappear[2]
25.Br, Ebrl, O7 p3+3 A(3) Go – is a. This F.D of male flower of musa b. The F.D of crotalaria juncea c. The F.D. of male flower of phyllanthus amaras d. The F.D of male flower of cocos nucifera[2]
26.What is plectostele – Give example.[2]
27.(I)) Esters formed between long-chain alcohol another negative. – A. a molecule with two or more & saturated fatty acid function group one +ve and (II) lipids have both hydrophobic & hydrophilic end known for permeability – B. fluid nature & selective (III) The amino acids are both acidic & basic exoskeleton of insects – C. waxy substance coating (IV) Zwitter is also called dipolar – D. amophoteric in nature[2]
28.Name any 2 bacteria diseases affecting Potato[2]
29.Name the two types of nuclear division.[2]
Part III — Long Answer Questions 10 × 5 = 50
Answer in detail. (Answer all questions.)
30.Notes on photosystem and Reaction centre.[5]
31.a) The study of fruits …….[5]
32.What is meant by the viability of seeds?[5]
33.Write the differences between ubiquinone and Cytochrome C.[5]
34.Write down the uses of Herbarium[5]
35.What are Quantosomes?[5]
36.Distinguish between Cyanophage and Mycophage[5]
37.Which is the lowest taxon in classification? Define.[5]
38.Differences Between Phellem and Phelloderm[5]
39.What are Xanthophylls?[5]
🔑 Show Answer Key — Set 2
- 1. a) C B D E A
- 2. (c) Phloem unloading
- 3. (b) Keys
- 4. b) Bluish biliprotein pigment
- 5. (b) Chloroplast
- 6. (b) Hevea brasiliensis
- 7. d. Heterocyst
- 8. c) Sero taxonomy
- 9. c) (I)(II)& (IV)
- 10. d.biennial
- 11. c. Worker bees
- 12. (c) amphibolic pathway
- 13. (a) 16
- 14. c. phosphodiester linkage
- 15. (c) Cross etal
- 16. Homoiomerous lichens have algal cells evenly and uniformly distributed throughout the entire thallus, mixed with fungal hyphae in a homogeneous manner without any distinct layering or organization. In contrast, heteromerous lichens display a distinct stratified structure with clearly defined layers: an upper cortex of fungal hyphae, a middle algal layer containing photosynthetic algal cells, and a lower cortex of fungal hyphae, with a medulla of loosely arranged hyphae in between. This structural difference affects their appearance, with homoiomerous lichens appearing more uniform and heteromerous lichens showing visible layering when sectioned.
- 17. In the Embden-Meyerhof-Parnas (EMP) pathway, phosphorylation and dephosphorylation reactions are catalyzed by specific enzymes. The enzymes involved in phosphorylation reactions are hexokinase, which phosphorylates glucose to glucose-6-phosphate, and phosphofructokinase, which catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate. These phosphorylation steps require energy input from ATP. The enzymes involved in dephosphorylation reactions are phosphoglycerate kinase, which catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP, forming ATP, and pyruvate kinase, which catalyzes the transfer of a phosphate group from phosphoenolpyruvate…
- 18. Secondary growth, which leads to an increase in the girth or diameter of the plant stem and root, is primarily brought about by the activity of two lateral meristems. These meristems are responsible for producing new cells that contribute to the secondary tissues. The two lateral meristems are the vascular cambium and the cork cambium. The vascular cambium is responsible for producing secondary xylem (wood) towards the inside and secondary phloem towards the outside, thus increasing the diameter of the vascular cylinder. The cork cambium, also known as phellogen, is responsible for forming the periderm, which includes the cork (phellem) and secondary cortex (phelloderm), replacing the epi…
- 19. The correct answer is (d) Both Assertion (A) and Reason (R) are false. The assertion states that non-cyclic photophosphorylation occurs in the stroma of chloroplasts, which is incorrect. Non-cyclic photophosphorylation actually occurs in the thylakoid membrane of the chloroplast, not in the stroma. The light-dependent reactions, including non-cyclic photophosphorylation, require the presence of photosystems II and I, electron transport chains, and ATP synthase, all of which are embedded in or associated with the thylakoid membrane. The stroma is the site of the light-independent reactions (Calvin cycle), not the light reactions. The reason states that there is a continuous flow of electro…
- 20. Nitrogen fixation without nodulation occurs in several plant-prokaryote associations where atmospheric nitrogen is converted to ammonia without the formation of specialized root nodules. In lichens, the photosynthetic partner is associated with cyanobacteria such as Anabaena and Nostoc, which fix atmospheric nitrogen. Anthoceros, a liverwort, forms a symbiotic relationship with the cyanobacterium Nostoc, allowing nitrogen fixation to occur within the plant tissues. Azolla, an aquatic fern, harbors the cyanobacterium Anabaena azollae in specialized leaf cavities, enabling nitrogen fixation without nodule formation. Cycas, a gymnosperm, maintains associations with cyanobacteria such as Anab…
- 21. Fleshy fruits are fruits with a soft, succulent pericarp that is edible and contains seeds. There are several types of fleshy fruits classified based on their structure and development. Berry is a fleshy fruit developed from a single carpel with seeds embedded in the pulp, such as banana, tomato, and grape. Drupe is a fleshy fruit with a hard, woody endocarp (stone) surrounding the seed, with examples including mango, coconut, and peach. Pome is a fleshy fruit where the receptacle forms the edible part along with the ovary wall, as seen in apple and pear. Aggregate fruits like strawberry develop from multiple carpels of a single flower. Accessory fruits like cashew apple have the receptac…
- 22. Trichophyton Tinea Microsporum Epidermophyton are some fungi causing skin problems
- 23. Organisms like Pseudomonas and Thiobacillus are of great significance in the nitrogen cycle because they carry out denitrification, a process in which nitrates are reduced back to nitrogen gas. Denitrification is the reverse of nitrogen fixation and nitrification, and these denitrifying bacteria release nitrogen gas back into the atmosphere. This process is crucial for maintaining a constant and balanced level of nitrogen in the atmosphere, preventing excessive accumulation of nitrates in soil and water bodies. Without denitrification, nitrogen would continue to accumulate in the biosphere, disrupting ecological balance and nutrient cycling.
- 24. The correct match is Diakinesis – Terminalisation of chiasmata occur and nucleolus disappear. During diakinesis, which is the final stage of prophase I in meiosis, the chiasmata move toward the ends of the bivalents in a process called terminalization. Additionally, the nucleolus disappears during diakinesis as the nuclear envelope begins to break down in preparation for metaphase I. The other stages have different characteristics: Zygotene is when synapsis of homologous chromosomes begins to occur, Pachytene is when synapsis is complete and bivalents are fully formed, and Diplotene is when the homologous chromosomes begin to separate slightly while chiasmata are still visible.
- 25. The floral diagram (F.D.) represented by Br, Ebrl, O7 p3+3 A(3) Go is the F.D. of the male flower of Phyllanthus amarus. This formula indicates the presence of bracts (Br) and bracteoles (Ebrl). The perianth (P) consists of two whorls of three tepals each (3+3), which are free. The androecium (A) has three stamens, which are free (3). The gynoecium (G) is superior (o) and has three carpels, which are fused (3), but in a male flower, the gynoecium is represented as rudimentary or absent, hence the 'o' indicating a superior ovary that is non-functional or absent in male flowers.
- 26. Plectostele is a type of stele in which the xylem plates alternate with the phloem plates in a radial arrangement. This arrangement creates a characteristic pattern where vascular tissues are interspersed with one another rather than forming concentric rings. The plectostele is found in certain pteridophytes, particularly in club mosses. A classic example of a plant exhibiting plectostele is Lycopodium clavatum, commonly known as the club moss or stag's horn moss, where this vascular arrangement is clearly observable in cross-sections of the stem.
- 27. (I) Esters formed between long-chain alcohol and saturated fatty acid – C. waxy substance coating exoskeleton of insects (II) Lipids have both hydrophobic and hydrophilic end known for permeability – B. fluid nature and selective (III) The amino acids are both acidic and basic – D. amphoteric in nature (IV) Zwitterion is also called dipolar – A. a molecule with two or more function groups one positive and one negative. Waxes are esters that provide protective coatings. Amphipathic lipids have both water-repelling and water-attracting regions, enabling selective permeability. Amino acids contain both carboxyl (acidic) and amino (basic) groups, making them amphoteric. Zwitterions are dipola…
- 28. Two bacterial diseases affecting potato plants are ringrot and scab. Ringrot is caused by the bacterium Clavibacter michiganensis subspecies sepedonicus. This disease causes necrotic lesions in the vascular tissues of the potato tuber, creating a ring-like pattern when the tuber is cut in cross-section. Scab is caused by the bacterium Streptomyces scabies. This disease produces rough, corky lesions on the surface of potato tubers, making them unsuitable for market. Both diseases are economically important and can significantly reduce potato yield and quality.
- 29. The two primary types of nuclear division are Mitosis and Meiosis. Mitosis is a process of cell division that results in two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. It is essential for growth, repair, and asexual reproduction. Meiosis, on the other hand, is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell. Meiosis is crucial for sexual reproduction, as it produces gametes (sperm and egg cells) or spores.
- 30. Thylakoid membrane contains photosystem I (PSI) and photosystem II (PSII) PS I is unstacked region of granum tàcing stroma ofchÍoroplast. PS II is found in stacked region of thylakoid membrane facing lumen of thylakoid. Each photosystem consists of central core complex (CC) and light harvesting complex (LHC) or Antenna molecules. The core complex consists of respective reaction centre associated with proteins, electron donors and acceptors. PSI – CCI consists of reaction centre P 700 and LHC – I PS II- CC II consists of reaction centre P680 and LHC – II Light harvesting complex consists of several chiorophylls, carotenoids and xanthophyll molecules. The main function of LHC is to harvesti…
- 31. Pomology is the study of fruits and their characteristics, including their development, classification, and uses. Ikebana is the Japanese art of flower arrangement that emphasizes aesthetic principles and the harmonious placement of flowers and plant materials. The botanical name of saffron flower is Crocus sativus, a plant valued for its stigmas which are used as a spice. Kurinji, scientifically known as Strobilanthus kunthianus, is a flowering plant that blooms once every twelve years in the Western Ghats of India, creating a spectacular blue carpet on the hillsides. Lodoicea maldivica, also called the double coconut or coco de mer, produces the world's largest fruit, which can weigh up…
- 32. The viability of seeds refers to their ability to germinate and produce a normal seedling under suitable conditions. It essentially indicates the living condition of the seed and its capacity to remain dormant yet alive. The shelf life of a seed, after which it loses its ability to germinate, is known as its viable period. This period varies significantly among different plant species, ranging from a few days to several centuries. For instance, Oxalis seeds have a very short viability, lasting only a few days. In contrast, Lotus seeds are known for their remarkable longevity, with some specimens germinating after more than 1000 years. The Judean Date palm, specifically the 'Methuselah' va…
- 33. Ubiquinone and Cytochrome C are both electron carriers in the electron transport chain, but they differ in their chemical nature, location, and function. Ubiquinone, also known as coenzyme Q, is a small, lipid-soluble molecule that serves as both an electron and proton carrier. It is located within the inner membrane of the mitochondria and is associated with Electron Transport System complex I, where it accepts electrons from NADH and transfers them to the next complex in the chain. Cytochrome C, in contrast, is a small protein molecule that is attached to the outer surface of the inner mitochondrial membrane. It functions as an electron carrier and is associated with Electron Transport…
- 34. Provides resource material for systematic research & studies A place for the orderly arrangement of voucher specimens Voucher specimen serves as a reference for comparing doubtful Newly collected fresh specimen Voucher specimens play a role in Studies like floristic diversity Environmental assessment Ecological mechanisms & Survey of unexplored area provides an opportunity for documenting biodiversity and studies related to the field of ecology & conservation biology.
- 35. They are physiological photosynthetic units, located on the inner membrane of thylakoid lamellae of size 180A X 160 A length & breadth. It was named by Park &Pickins( 1964). One quantosome contains about 230 chlorophyll molecules. It constitutes a photosynthetic unit responsible for the production of one O 2 molecule or reduction of one CO 2 molecule.
- 36. Cyanophage Mycophage 1 Vims infecting blue green Algae are known as Cyanophage Vims allacking fungi are called Mycovimses or Mycophage 2 1st reported by Safferman and Mores(1963) 1st reported by Holling(1962) 3 Eg. Lyngbuya, Plectonema Eg. Myc ovims attacking Mushrooms
- 37. Species is indeed considered the lowest or most fundamental taxon in biological classification. It is precisely defined as a group of individuals that are closely resembling each other in morphological, anatomical, biochemical, and genetic characteristics, and, crucially, are capable of interbreeding among themselves under natural conditions to produce fertile offspring. This ability to interbreed and produce fertile progeny is a key criterion for delineating a species, particularly in sexually reproducing organisms. Individuals within a species share a common gene pool and are reproductively isolated from other species. This concept helps to organize the vast diversity of life into discr…
- 38. Phellem and phelloderm are two distinct tissues produced by the phellogen during secondary growth, differing in their position, structure, function, and composition. Phellem, commonly called cork, is formed on the outer side of the phellogen. Its cells are compactly arranged in regular tiers and rows without any intercellular spaces, creating a dense, impermeable layer. The cells of phellem are non-living at maturity and possess suberized walls, meaning they are impregnated with suberin, a waxy, water-resistant substance. This structure makes phellem primarily protective in function, serving as a barrier against water loss, mechanical damage, and pathogen invasion. Lenticels, which are ra…
- 39. Xanthophylls are yellow pigments with the molecular formula C40H56O2. They are chemically similar to carotenes but differ in that they contain oxygen atoms in their structure. Xanthophylls are accessory pigments in photosynthesis that absorb light energy and transfer it to chlorophyll. Common examples of xanthophylls include lutein, violaxanthin, and fucoxanthin. Lutein is particularly notable as it is responsible for the yellow color changes observed in leaves during the autumn season when chlorophyll breaks down and the yellow xanthophyll pigments become visible. These pigments play important roles not only in light harvesting but also in protecting the photosynthetic apparatus from exc…
Brain Grain · braingrain.in
Botany — Practice Paper · Set 3
Class: 11Samacheer KalviMax Marks: 93
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 15 × 1 = 15
Choose the correct answer. (Answer all questions.)
1.Which of the following reaction is not involved in Krebs cycle.(a) Shifting of phosphate from 3C to 2C(b) Splitting of Fructose 1,6 bisphosphate of into two molecules 3C compounds.(c) Dephosphorylation from the substrates(d) All of these[1]
2.Phosphorylation taking place during respiration is called as:(a) Photophorylation(b) Oxidative phosphorylation(c) Reductive phosphorylation(d) None of the above[1]
3.Which of the following process is called reverse of Glycolysis? a) CO 2 reduction b) RUBP carboxylation c) RUBP regeneration d) ATP synthesis[1]
4.Climbers are also called as …………….(a) herbs(b) trees(c) vines(d) shrubs[1]
5.In the sugarcane plant, the dicarboxylic acid pathway was first discovered by:(a) Hatch and Slack(b) Kortschak, Hart and Burr(c) Calvin and Benson(d) Mitchell and Root[1]
6.Recombination is the result of a. Binary fission b. Asexual reproduction c. Sexual reproduction. d. Vegetative propagation[1]
7.Many cells function properly and divide mitotically even they do not have a) Plasma membrane b) Cyto skeleton c) Mitochondria d) Plastids[1]
8.Match the correct combination. Minerals Role A Molybdenum 1. Chlorophyll B Zinc 2. Methionine C Magnesium 3. Auxin D Sulphur 4. Nitrogenase a) A-1 B-3 C-4 D-2 b) A-2 B-1 C-3 D-4 c) A-4 B-3 C-1 D-2 d) A-4 B-2 C-1 D-3[1]
9.Postelia palmaeformis is commonly known as a. Sea kelp b. Sea shell c. Sea palm d. Sea worth[1]
10.The correct statement regarding Blue Green Algae is a. Lack of motile structures b. Presence of cellulose in cell wall c. Absence of mucilage around the thallus d. Presence of Floridian starch[1]
11.Anastral mitosis is the characteristic feature of a) Lower animals b) Higher animals c) Higher plants d) All living Organism[1]
12.The general form of a plant is referred to as …………….(a) habitat(b) structure(c) habit(d) shape and size[1]
13.Solute potential is also known as a) Water potential b) Pressure potential c) Osmotic potential d) Maic potential[1]
14.Delay in flowering is due to the deficiency of a) N, S, Mo b) Ca, Mg, Mn c) C, H, O d) N,P,K[1]
15.Identify the correct statement: (i) Sulphur is essential for amino acids Cystine and Methionine (ii) Low level of N, K, S and Mo affect the cell division (iii) Non – leguminous plant Alnus which contain bacterium Frankia (iv) Denitrification carried out by nitrosomonas and nitrobacter.(a) (i), (ii) are correct(b) (i), (ii), (iii) are correct(c) I only correct(d) all are correct[1]
Part II — Short Answer Questions 14 × 2 = 28
Answer briefly. (Answer all questions.)
16.Why is it essential to do classification?[2]
17.I) The bundle cap of Dicto stem is known as Hard bast. II) The bundle cap of Dicot stem is parenchymatous III) The bundle sheath of Dicot leaf is sclerenchymatous walls of Endodermis in Endodermis is known as the outermost layer of stele. IV) In Angiosperms pericycle gives rise to lateral roots[2]
18.Name the four types of ascocarps produced by ascomycetes.[2]
19.What are the deficiency symptoms of nitrogen?[2]
20.(i) Fungi play important role in soil conservation (ii) Vascular cryptogams were predominant in the paleozoic era (iii) Gymnosperms were dominant in the early cretaceous period. (iv) Angiosperms appeared during the Jurassic period[2]
21.(i) Poly-B hydroxybutysate is a microbial plastic which is biodegradable (ii) Transfer of DNA from one bacterium to another is known as transduction (iii) Micrococcus must have oxygen to survive-known as an obligate aerobe (iv) Spirulina is rich in carbohydrates so treated as an alternative food.[2]
22.Draw the structure of the lysosome.[2]
23.Name 2 hormones involved in Nodule formation.[2]
24.Describe briefly radial types of vascular Bundles.[2]
25.Classify terrestrial habitats[2]
26.Label the given diagram[2]
27.Name few Renowed mycologists?[2]
28.Label the diagram properly.[2]
29.Differentiate between Anaphase I & Anaphase II of Meiosis.[2]
Part III — Long Answer Questions 10 × 5 = 50
Answer in detail. (Answer all questions.)
30.State Koroperkappe theory.[5]
31.What is impaction in seed dormancy.[5]
32.Annual rings are not clear and distinct in desert trees and seashore plants – Justify.[5]
33.What is meant by kranz Anatomy? What is its importance.[5]
34.Define, hydathode?[5]
35.Differentiate between sieve tubes and vessels[5]
36.Write an essay on the role of ethylene on plant physiology and agriculture.[5]
37.What are the inducers of stomatal closure.[5]
38.Explain the opening and closing of stomata by a starch – sugar – Interconversion theory.[5]
39.Give an account of Ribosomes:[5]
🔑 Show Answer Key — Set 3
- 1. (d) All of these
- 2. (b) Oxidative phosphorylation
- 3. a) CO 2 reduction
- 4. (c) vines
- 5. (b) Kortschak, Hart and Burr
- 6. c. sexual reproduction
- 7. d) Plastids
- 8. c) A-4 B-2 C-1 D-3
- 9. c. Sea palm
- 10. a. lack of motile structure
- 11. c) Higher plants
- 12. (c) habit
- 13. c. Osmotic potential
- 14. a) N,S,Mo
- 15. (b) (i), (ii), (iii) are correct
- 16. To relate on the basis of common features To define, on the basis of salient features To know the relationship among different groups. To understand evolutionary relationship.
- 17. b) False – True – False – True. The bundle cap of dicot stems is composed of sclerenchyma, not parenchyma, making the first statement false. The bundle cap is indeed parenchymatous in some cases, but more accurately it is sclerenchymatous, making the second statement true. The bundle sheath of dicot leaves is sclerenchymatous, but the statement about endodermis being the outermost layer of stele is false; the pericycle is the outermost layer of the stele. In angiosperms, the pericycle does give rise to lateral roots, making the fourth statement true.
- 18. Ascomycetes, a diverse group of fungi, produce their sexual spores (ascospores) within specialized sac-like structures called asci. These asci are typically enclosed within fruiting bodies known as ascocarps. Four distinct types of ascocarps are recognized based on their structure and mode of development: Cleistothecium, which is a completely closed, spherical ascocarp; Perithecium, a flask-shaped ascocarp with a distinct opening called an ostiole; Apothecium, an open, cup-shaped or saucer-shaped ascocarp; and Pseudothecium, which resembles a perithecium but develops within a stroma.
- 19. Nitrogen deficiency in plants manifests through several characteristic symptoms. Chlorosis, or yellowing of leaves, is one of the primary symptoms, typically appearing first in older leaves since nitrogen is a mobile element. Stunted growth occurs as nitrogen is essential for protein synthesis and cell division, so its deficiency severely restricts plant development. Anthocyanin formation, which causes a purple or reddish coloration in leaves and stems, also occurs due to the accumulation of sugars when nitrogen is insufficient for normal metabolism. These symptoms collectively indicate inadequate nitrogen availability for the plant's metabolic and structural requirements.
- 20. (i) False – Fungi do not play a direct role in soil conservation; rather, they are decomposers that break down organic matter. (ii) True – Vascular cryptogams (ferns and lycophytes) were indeed the predominant land plants during the Paleozoic era. (iii) False – Gymnosperms were dominant during the Mesozoic era, particularly the Jurassic and Cretaceous periods, not the early Cretaceous alone as the primary dominants. (iv) False – Angiosperms first appeared during the Cretaceous period, not the Jurassic period. They diversified and became dominant later in the Cretaceous and subsequent periods.
- 21. The correct evaluation of these statements is: (i) Poly-B hydroxybutyrate is indeed a microbial plastic produced by certain bacteria and is biodegradable, making this statement True. (ii) Transduction refers to the transfer of DNA from one bacterium to another via bacteriophages, not direct bacterial transfer, making this statement False. (iii) Micrococcus is an obligate aerobe that requires oxygen to survive, making this statement True. (iv) Spirulina is rich in proteins and other nutrients, not primarily carbohydrates, and is used as a nutritional supplement and alternative food source, making this statement False. The correct answer is True, False, True, False.
- 22. A lysosome is a membrane-bound organelle with a spherical or oval shape, typically ranging from 0.2 to 0.5 micrometers in diameter. It is bounded by a single phospholipid bilayer membrane that encloses a matrix containing various hydrolytic enzymes such as proteases, lipases, nucleases, and phosphatases. The interior of the lysosome appears electron-dense under electron microscopy due to the presence of these digestive enzymes. The structure can be represented as a circular or oval outline with a surrounding membrane and a granular interior representing the enzyme-containing matrix. Lysosomes are often called the 'suicide bags' of the cell because they contain powerful digestive enzymes c…
- 23. During nodule formation in leguminous plants, two hormones play key roles in promoting the development of root nodules. Cytokinin, produced by the nitrogen-fixing bacteria (such as Rhizobium), stimulates cell division in the root cortex. Auxin, produced by the host leguminous plant, also promotes cell division and elongation. Together, these two hormones work synergistically to induce the formation of nodule structures where the symbiotic bacteria reside and fix atmospheric nitrogen.
- 24. Radial vascular bundles are a type of bundle arrangement found primarily in roots of both monocots and dicots. In this arrangement, the xylem and phloem tissues are positioned on different radii, meaning they alternate with each other around the central axis of the root. The xylem typically forms radiating arms or ridges that extend from the center toward the periphery, while the phloem groups are located in the spaces between these xylem arms. The different tissues are separated and organized by parenchymatous tissue, which fills the spaces between the vascular elements. This radial arrangement provides structural support to the root and allows for efficient absorption and conduction of…
- 25. Terrestrial habitats can be classified based on soil moisture and environmental conditions into several types. Mesophytes are plants that grow in habitats with soil containing sufficient water and moderate conditions, such as Azadirachta indica (neem tree). Xerophytes are plants adapted to dry habitats with low water availability, including examples like Opuntia and Euphorbia. Psammophytes are specialized plants that grow on sandy soils and sand dunes, such as Spinifex littoralis. Lithophytes are plants that grow on rocky surfaces and rocky habitats, including lichens and Ficus species. Each of these plant types possesses specific morphological and physiological adaptations that enable th…
- 26. A- Pedicil B – Perianth C – Epipetalous stamens D- Ovary
- 27. Several renowned mycologists have made significant contributions to the field of mycology. Arthur H.R. Buller and John Webster are prominent Western mycologists known for their extensive work on fungi. D.L. Hawksworth and G.C. Ainsworth are also notable mycologists who have contributed substantially to fungal taxonomy and classification. In India, B. Mundkur, K.C. Mehta, C.V. Subramanian, and T.S. Sadasivam are recognized as important mycologists. E.J. Butler is regarded as the father of Indian mycology and made pioneering contributions to the study of fungi in India. These scientists have collectively advanced our understanding of fungal diversity, classification, and ecology.
- 28. The diagram illustrates a bivalent or tetrad structure formed during meiosis, specifically prophase I. A points to Non-sister Chromatids, which are chromatids belonging to homologous chromosomes that are paired up. These are the sites where crossing over, or genetic recombination, typically occurs. B indicates the Centromere, the constricted region on each chromosome that holds the sister chromatids together. C highlights the Chiasma (plural: chiasmata), which is the visible manifestation of crossing over between non-sister chromatids, appearing as an X-shaped structure where homologous chromosomes are still connected. D labels the entire structure as a Bivalent or Tetrad, referring to th…
- 29. Anaphase I and Anaphase II are two distinct stages of meiosis with important differences. During Anaphase I, homologous chromosomes separate and move toward opposite poles of the cell. Each chromosome still consists of two sister chromatids joined at the centromere, so the number of chromosomes moving to each pole is half the diploid number. This separation of homologous pairs is the key event that reduces the chromosome number. In contrast, during Anaphase II, sister chromatids separate at the centromere and move toward opposite poles. At this stage, the cell is already haploid, and the separation of sister chromatids produces individual chromosomes. Therefore, the fundamental difference…
- 30. The Korper Kappe theory was proposed by schuepp. This theory is equivalent to Tunica corpus theory of shoot apex. The two divisions are distinguished by the type of T division. Korper is characterised by inverted T divisions Kappe is characterised by straight T divisions.
- 31. In some seeds water and oxygen are unable to penetrate micropyle due to blockage by cork cells. These seeds are shaken vigorously to remove the plug The process of removing the plug or block is called impactation.
- 32. In the desert, as well seashore regions the climatic condition remain the same throughout the year. Secondary growth in plants is influenced by seasonal changes since in these areas seasonal changes are not significant enough to bring in distinct Annual rings with early and latewood formation alternatively.
- 33. Kranz anatomy is a specialized leaf anatomy characteristic of C4 plants, such as maize, sugarcane, and sorghum, which enables them to efficiently fix carbon dioxide at low concentrations and high temperatures. The term 'Kranz' is German for 'wreath' or 'halo,' referring to the distinctive arrangement of cells around the vascular bundles. In plants exhibiting Kranz anatomy, the vascular bundles are surrounded by two concentric rings of cells. The inner ring consists of large, thick-walled bundle sheath cells that are rich in chloroplasts and often contain starch grains. These bundle sheath cells are typically large and have few, if any, intercellular spaces. The outer ring is composed of m…
- 34. A hydathode is a specialized type of epidermal pore found in higher plants that functions in the process of guttation, the release of excess water from leaves. Structurally, hydathodes are modified stomata, though they differ from typical stomata in their function and location. Hydathodes are usually located at the leaf tips or margins, particularly at the leaf teeth or serrations, where they facilitate the exudation of water droplets. These structures are especially prominent in submerged aquatic plants such as Ranunculus fluitans, where they help regulate water balance in the plant body. Hydathodes are also found in many herbaceous land plants, particularly those growing in conditions o…
- 35. Sieve tubes and vessels are both important conducting elements of vascular tissue but differ in their location, composition, and function. Sieve tubes are components of the phloem and are formed by the fusion of cells to create a syncyte, which is a multinucleate structure. Although sieve tubes are syncytes, they are living cells that contain a lining layer of cytoplasm, making them known as living syncytes. The nucleus is absent in mature sieve tubes, but the presence of cytoplasm allows them to conduct organic food materials. Sieve tubes are associated with companion cells that help regulate their function. Vessels, on the other hand, are components of the xylem and are also syncytes fo…
- 36. Almost all plant tissues produce ethylene gas in minute quantities. 1. Discovery: In 1924, Denny found that ethylene stimulates the ripening of lemons. In 1934, R. Gane found that ripe bananas contain abundant ethylene. In 1935, Cocken et al., identified ethylene as a natural plant hormone. 2. Occurrence: Maximum synthesis occurs during climacteric ripening of fruits and tissues undergoing senescence. It is formed in almost all plant parts like roots, leaves, flowers, fruits and seeds. 3. Transport in plants: Ethylene can easily diffuse inside the plant through intercellular spaces. 4. Precursor: It is a derivative of amino acid methionine, linolenic acid and fumaric acid. 5. Bioassay (Ga…
- 37. Stomatal closure is a critical physiological response in plants, primarily regulated to conserve water, especially under stress conditions. Various factors and substances can induce this closure. Natural anti-transpirants are substances that naturally occur in plants and help reduce water loss by inducing stomatal closure. For example, an increase in carbon dioxide (CO2) concentration within the leaf can inhibit photorespiration and directly induce stomatal closure, as the plant senses a sufficient CO2 supply for photosynthesis. Additionally, certain chemicals, when applied as a foliar spray, can effectively induce stomatal closure for an extended period, typically lasting two to three we…
- 38. i) Lloyd (1908) According to him, turgidity of Guard cell is due to interconversion of starch → sugar * Day time: Guard cells have sugar → so turgid → opening of stomata * Nighttime: Guard cells have starch → so loose turgidity (become flaccid) → closure of stomata ii) Sayre (1920) According to him, the pH of Guard cell determine opening and closing of stomata * Day time: Guard cells have high pH →so turgid → opening of stomata * Nighttime: Guard cells have low pH → become flaccid → closure of stomata to be elaborate * Day time: Utilisation of CO 2. in photosynthesis → Starch into sugar → high pH → high Turgor pressure→Opening of Stomata * Night Time: No photosynthesis, so the accumulatio…
- 39. Ribosomes are dense particles observed in the electron microscope, first by George Palade in 1953. They are not membrane-bound organelles and are crucial for protein synthesis. Each ribosome is made up of two round subunits, one large and one small, which come together to form a complete functional unit. The cohesion of these subunits requires magnesium ions (Mg++). Ribosomes can be formed through denovo synthesis, auto-replication, and originate from the nucleolus. Their primary function is to serve as the sites of protein synthesis, where genetic information from mRNA is translated into polypeptide chains. Ribosomes are composed of approximately 60% ribosomal RNA (rRNA) and 40% protein.…