Plant Growth and DevelopmentNEET Botany · Class 11 · NCERT Chapter 15

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Dr. F. Went's experiment demonstrated that the growth-promoting substance from coleoptile tips could be transferred to agar and then induce bending in freshly-cut coleoptile stumps. This experiment was crucial for the isolation and identification of auxin, making option (a) correct.

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Deficiency symptoms of mobile nutrients like nitrogen and potassium appear first in senescent leaves, as these nutrients are transported from older to younger parts of the plant. NCERT XII chapter Plant Growth and Development explains that mobile nutrients are remobilized from older to newer tissues, so option (a) is correct.

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The seedlings have become white due to the absence of light, which prevents chlorophyll synthesis and causes etiolation. NCERT XII chapter Plant Growth and Development describes etiolation as the elongation and whitening of stems in the absence of light, so option (c) is correct.

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Abscissic acid is known as the 'stress hormone' because it plays a crucial role in plant responses to environmental stresses such as drought and cold. NCERT XII chapter Plant Growth and Development highlights this role, so option (a) is correct.

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As various ions from the soil are actively transported into the vascular tissues of the roots, water follows and increases the pressure inside the xylem i.e., root pressure (positive pressure).

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Avena coleoptile curvature test is the bioassay forauxin.

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I1 I2 =25 1 ⇒A1 A2 =5 1 Amax Amin =5+1 5−1 =6 4 =3 2 Imax Imin =(3 2 ) 2 =9 4

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or bonus Macronutrients are required in greater amount which is 1 mg-gram of plant dry weight. None of the options are correct w.r.t. question statement. However, the option (4) seems to be more appropriate than the rest.

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Avena curvature bioassay is done to test the function of IAA.

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Auxins prevent premature leaf and fruit fall. NAA prevents fruit drop in tomato; 2,4-D prevents fruit drop in Citrus.

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Potassium is responsible for maintaining turgor in cells by regulating water movement and osmotic pressure. NCERT XII chapter Plant Growth and Development highlights the role of potassium in cell turgidity, so option (a) is correct.

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Stomatal movement is influenced by light, temperature, and ${\text{CO}}_2$ concentration, but not by ${\text{O}}_2$ concentration. NCERT XI chapter Plant Growth and Development outlines these factors, so option (a) is correct.

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Allergy is type of inflammation specific to respiratory tract

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Ref. XI NCERT Chapter- 1, Page No. 07

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Ref. XII NCERT Chapter- 06, Page No. 119

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Gibberellins, when sprayed on sugarcane, promote stem elongation and increase the yield. NCERT XII chapter Plant Growth and Development highlights the role of gibberellins in stimulating cell elongation and growth, so option (b) is correct.

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Secondary metabolites like nicotine, strychnine, and caffeine are produced by plants for defence against herbivores and pathogens. NCERT XII chapter Plant Growth and Development explains that these compounds have ecological roles in plant defence, so option (c) is correct.

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The process responsible for the loss of water in liquid form from the tips of grass blades at night and in early morning is guttation, not transpiration. However, among the given options, transpiration is the closest related process, but it is not the correct answer. The correct answer is not listed, but if we must choose, option (a) is the closest. However, the correct term is guttation, which is not listed.

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Gibberellic acid is a plant hormone that promotes seed germination, not dormancy. Abscisic acid, phenolic acid, and para-ascorbic acid are known to inhibit seed germination and maintain dormancy, so option (a) is correct.

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Sapwood is not the innermost secondary xylem; it is the outer, living part of the secondary xylem that is involved in water and mineral conduction. Heartwood is the inner, non-living part that provides mechanical support and is darker in color due to deposits of tannins, resins, and oils. Therefore, option (c) is incorrect.

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Nitrogenase catalyzes the reduction of atmospheric nitrogen to ammonia and hydrogen gas. The reaction produces ammonia and hydrogen, as described in NCERT XI chapter Plant Growth and Development, so option (d) is correct.

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- Iron is required for chlorophyll biosynthesis.
- Zinc is essential for IAA biosynthesis.
- Boron is necessary for pollen germination.
- Manganese is involved in the photolysis of water.

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The process of growth is maximum during the log phase, when cells divide rapidly and the population increases exponentially. NCERT XII chapter Plant Growth and Development describes the log phase as the period of active cell division and growth, so option (a) is correct.

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In one turn of the citric acid cycle, there is one substrate-level phosphorylation event, which occurs during the conversion of succinyl-CoA to succinate. NCERT XI chapter Plant Growth and Development outlines the steps of the citric acid cycle, confirming option (b) is correct.

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- Cells with active cell division capacity are found in meristematic tissue (ii).
- Tissue having all cells similar in structure and function is simple tissue (iv).
- Tissue having different types of cells is vascular tissue (i).
- Dead cells with highly thickened walls and narrow lumen are sclereids (iii).

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The ability of plants to form different kinds of structures in response to environmental conditions or phases of life is called plasticity. NCERT XII chapter Plant Growth and Development defines plasticity as the capacity of plants to modify their growth and development in response to environmental cues, so option (c) is correct.

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2, 4-D is a synthetic auxin used as a herbicide to control broadleaf weeds. NCERT XII chapter Plant Growth and Development discusses auxins, including 2, 4-D, for their role in weed control, so option (c) is correct.

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- Lenticels facilitate the exchange of gases (iii).
- Cork cambium is formed by the phellogen (i).
- Secondary cortex is the phelloderm, which is the inner secondary tissue (iv).
- Cork is characterized by suberin deposition (ii).

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The site of light perception in plants during photoperiodism is the leaf. NCERT XII chapter Plant Growth and Development states that leaves, particularly the phytochrome in the leaves, are responsible for sensing light signals, so option (d) is correct.

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- Cohesion is the mutual attraction among water molecules.
- Adhesion is the attraction of water molecules towards polar surfaces.
- Surface tension is the property of a liquid to resist external forces due to cohesion.
- Guttation is the exudation of water in liquid form from uninjured leaf margins.
Thus, the correct match is (a) (ii), (b) (i), (c) (iv), (d) (iii), so option (d) is correct.

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Amino acids and glucose are primary metabolites, essential for basic metabolic processes. Secondary metabolites, such as morphine, codeine, vinblastin, curcumin, rubber, and gums, are not directly involved in these processes but have specific roles in plant defense and communication, so option (b) is correct.

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The girdling experiment shows that phloem is the tissue responsible for translocation of food; and that transport takes place in one direction i.e. towards the root. - 44 - NEET (UG)-2022 (Code-Q1)

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The symplastic system is system of interconnected protoplasts. Neighbouring cells are connected through cytoplasmic strands that extend thro ugh plasmodesmata. The water travels through cell cytoplasm and plasmodesmata, hence the movement is relatively slower. Symplastic movement is aided by cytoplasmic streaming.

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Ethylene is a gaseous plant hormone. It induces development of adventitious roots on various types of cutting. It promotes the development of lateral roots and growth of root hairs. Cytokinin helps to overcome the apical dominance. Auxin is used to kill dicot weeds. Gibberellin speeds up the malting process

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Ethylene increases the number of female flowers and fruits in certain plants such as cucumber. Gibberellins are used to increase the size of fruits in some plants.

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If some solute is dissolved in pure water, the solution has lower free water and the concentration of water decreases, reducing it’s water potential. The magnitude of this lowering due to dissolution of a solute is called solute potential.

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Ethylene promotes internode and petiole elongation in deep water rice, allowing the plant to grow taller and keep its leaves above water. NCERT XII chapter Plant Growth and Development discusses the role of ethylene in this adaptive response, so option (d) is correct.

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In tissue culture, leaf mesophyll cells lose their specialised functions and revert to a meristematic state, forming callus. This process is known as dedifferentiation, as described in NCERT XII chapter Plant Growth and Development, so option (c) is correct.

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Gibberellic acid (GA) is known to hasten the maturity period in juvenile conifers, leading to early seed production. NCERT XII chapter Plant Growth and Development discusses the role of GA in promoting flowering and breaking dormancy, so option (c) is correct.

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Radicle is destined to form root. In the given diagram ‘C’ represent radicle - 47 - NEET (UG)-2024 (Code-Q1)

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Auxin does not affect mature monocot plants. In monocots, especially grasses show limited translocation and cause rapid degradation of external auxin.

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Totipotency is defined as the capacity to generate a whole plant from any cell of the plant.

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Sugarcanes store carbohydrate as sugar in their stems. Spraying sugarcane crop with gibberellins increases the length of the stem, thus increasing the yield.

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Cytokinins help to overcome apical dominance. They promote nutrient mobilisation which helps in the delay of leaf senescence.

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Scutellum is cotyledon of monocot seed.

Groundnut seed is non-albuminous seed.

Epiblast is rudimentary cotyledon in monocot seed.

Perisperm is persistent nucellus.

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Statement (A) is correct as auxins can induce parthenocarpy. Statement (B) is correct as plant growth regulators can both promote and inhibit growth. Statement (C) is correct as dedifferentiation is necessary for re-differentiation. Statement (D) is incorrect as abscisic acid generally inhibits growth. Statement (E) is incorrect as apical dominance inhibits the growth of lateral buds. Therefore, option (a) is correct.