Which of the following is not an action of ethylene?
1. Induces leaf abscission
2. Inhibits root hair growth - decreasing the efficiency of water and mineral absorption
3. Induces the growth of adventitious roots during flooding
4. Stimulates epinasty - leaf petiole grows out, leaf hangs down and curls into itself
Enhanced root hair production, which increases the root surface area for nurient uptake, is a typical adaptive response of plants to photosphate (pi) starvation.
The formation of interfascicular cambium in plants is due to:-
Read page 245 of XI NCERT
Heterophyllous development due to environment is an example of:-
1. Developmental noise
2. Norm of the reaction
Read page 246 of XI NCERT
Gibberellic acid is a/an:-
1. lndole compound
3. Adenine derivative
Page 247 of XI NCERT
The PGR used to initiate flowering and for synchronizing fruit-set in pineapples is:
1. Abscisic acid
Read page 250 of XI NCERT book
Cytokinin does not help in:
1. Lateral shoot growth
2. Overcoming apical dominance
3. Adventitious shoot formation
4. Promoting leaf senescence
Read page 250 of XI NCERT
In most situations, which of the following acts as an antagonist to Gas?
Read page 250 of XI NCERT
Which of the following is the site for perception of light/dark in plants?
1. Root apex
2. Shoot apex
Read page 252, Xl NCERT
A flash of red light followed by a flash of far-red light given during the middle of the night to a short-day plant will likely
1. cause increased flower production.
2. have no effect upon flowering.
3. inhibit flowering.
4. stimulate flowering.
Phytochromes are characterised by a red/far-red photochromicity. Photochromic pigments change their "colour" (spectral absorbance properties) upon light absorption. In the case of phytochrome the ground state is Pr, the r indicating that it absorbs red light particularly strongly. The absorbance maximum is a sharp peak 650-670 nm. But once a red photon has been absorbed, the pigment undergoes a rapid conformational change to form the pfr state. Here fr indicates that now not red but far-red (also called "near infra-red";705-740 nm) is preferentially absorbed. when pfr absorbs far-red light it is converted back to pr. Hence, red light makes pfr, far-red light makes pr. In plants at least pfr is the physiologically active or "signalling" state.
Both red and blue light are involved in?
1. stem elongation.
3. positive phototropism.
4. tracking seasons.
Different organs of the plant may exhibit different phototropic reactions to different wavelengths of light. Stem tips exhibit positive phototropic reactions to blue light, while root tips exhibit negative phototropic reactions to blue light. Both root tips and most stem tips exhibit positive phototropism to red light.