Plant Growth and Development Test - 82

Gibberellin induces stem elongation in rosette plants. Cabbage is a rosette plant with profuse leaf growth and retarded internodal length. Just prior to flowering, internodes elongate enormously. This is called as bolting. Bolting needs either long days or cold nights. When a cabbage head is kept under warm nights, it retains its rosette habit. Bolting can be induced artificially by the application of gibberellins under normal conditions. 

Abscisic acid is a stress hormone which is released during when the plant is in stress condition but not used for ripening the fruits like mango, orange, pineapple etc.

Cytokinins stimulate cell division, even in non-meristematic cells, in presence of auxin. They are most abundant in the growing tissues which are active site of cell division, for example: root, embryos, fruits etc. Coconut water is the liquid endosperm, the actively dividing tissue which serves as nutrition source for developing coconut embryo. Coconut water is used as growth promoter of developing embryos in tissue culture studies. It stimulates the growth of cultures of embryo due to presence of cytokinins. This makes option D correct. Abscisic acid (ABA) is a growth retardation hormone which inhibits seed germination and seedling growth. This makes option C incorrect as endosperm does not have growth retardation hormone. Option A is incorrect as auxin is the hormone of cell division and cell expansion, i.e., overall growth, while endosperm carries the hormone for cell division to increase the cell number only. Option B is incorrect as gibberellins are the hormone of stem elongation in genetic dwarf plants only.

The statement I is incorrect as Lutein is deoxygenated hydrocarbon as it is a carotene.
Warburg and his colleagues showed an inhibitory effect of oxygen on photosynthesis since oxygen serves as the competitive inhibitor of carbon dioxide during carbon fixation and there is the simultaneous stimulatory effect of oxygen on photorespiration; the whole phenomenon is also known as the Warburg effect which makes statement II correct.
Statement III is incorrect as UAA (Ochre) and UAG (Amber) are among the three stop codons that cause termination of protein synthesis and does not code for any amino acid.
Statement IV is correct as Richmond-Lang effect refers to delay of senescence in leaves and other plant parts as a result of regulation of protein synthesis and nutrient mobilization by cytokinins.
Statement II and IV are correct. 

Zeatin is the plant hormone belongs to cytokinin but not to auxin. 

Plant growth regulators or growth hormones play a crucial role in the growth and behavioral processes in the plant's life cycle. Also known as phytohormones these are present in the plants for eg. Auxins which are the naturally occurring carbon containing plant growth substances create a pattern of distribution in the plant body which works as the key factor for its growth, form and shape of plant body, direction and strength of organs, and their mutual interaction and its reaction to environment. Uneven distribution of auxin results in uneven plant tissue growth. Thus, the correct answer is option A.

Avena curvature test is bioassay for examining the activity of auxins, which checks the ability of auxins to induce cell elongation in coleoptiles, whose plant tips have been cut.

Cytokinins are the plant growth hormones that play a major role in the cell division and also in the plant development. Leaf senescence is a final stage of the leaf development as all the nutrients will be distributed to other parts and is also defines as the  decline in leaf cytokinin. If there is an endogenous application of cytokinin there will be increase in the cytokinin content and delay senescence. Hence, the option A is correct. 

Ethylene is naturally produced by plant cells.