Free Plant Growth And Development (Daily Quiz: 10) NEET Biology Questions & Answers with Detailed Explanation & Full Review

Answer: (a)

Auxin is a growth promoting phytohormone. It moves mainly from the apical to the basal end (basipetally). This type of unidirectional transport is termed polar transport. Auxin is the only plant growth hormone known to be transported polarly. Recently it has been recognized that a significant amount of auxin transport also occur acropetally (from basal end to the apical end) in the root.

Answer: (c)

Statement (i) and (ii) are correct. Gibberellins are not responsible for immature falling of leaves. Ethylene and abscisic acid generally have a negative role and are responsible for immature falling of leaves, rapid fading of flowers, inhibiting germination etc.

Answer: (b)

Nastic movements occur in response to a stimulus. It is independent of its direction. They are shown by bifacial organs (leaves, sepals, petals) and are in response to diffused external stimulus.

Seismonastic movements are due to shock or touch stimulus. Such movements are shown by Mimosa pudica. The leaf of Mimosa is compound having four pinna and each pinna is having many pinnules. If a terminal pinnule is touched, the whole leaf droops down. This is due to fact that at the bases of pinnules, pinna and whole leaf, swollen structure called pulvinus is present and drooping is due to loss of turgidity of lower portion of pulvinus.

Answer: (a)

Less of chlorophyll and degeneration of proteins are the two important symptoms of senescence. Cytokinins delay these processes and, thus the senescence is also delayed. This effect of cytokinin is known as Richmond-Lang effect.

Answer: (d)

A : Zeatin is derived from the purine base called adenine. Zeatin belongs to the family of plant-growth hormones called cytokinins and was discovered in immature corn kernels from the genus Zea.

B : Florigen (or flowering hormone) is the hypothesized hormone-like molecule responsible for controlling and/or triggering of flowering in plants. It is produced in the leaves, and acts in the shoot apical meristem of buds and growing tips.

C : Indole-3-butyric acid (IBA) is a natural plant hormone in the auxin family and is an ingredient in many commercial horticultural plant rooting products. It is used for stimulating plant growth and root formation.

D : Naphthalene acetic acid (NAA) is a synthetic plant hormone in the auxin family. It is toxic to plants at high concentrations. It induces the formation of more fertile branches in cotton plants.