Following are some statements regarding plant growth hormones.
1. Ethylene regulates abscission.
2. Gibberellins do not play any role in flowering.
3. Auxin and cytokinin promote cell division.
4. Over-expression of cytokinin oxidase would promote root growth.
5. ABA inhibits root growth and promotes shoot growth at low water potential.
6. ABA promotes leaf senescence independent of ethylene.
Which one of the following combinations of above statements is correct?
1, 3 and 6
4, 5 and 6
2, 3 and 4
2, 4 and 5
Gibberellins do play a significant role in flowering, particularly in the regulation of flowering time and flower development in plants.
Gibberellins are a class of plant hormones that regulate various aspects of plant growth and development, including flowering. They are involved in promoting the transition from vegetative growth to reproductive growth, which includes the induction of flowering.
over-expression of cytokinin oxidase would not promote root growth. Cytokinin oxidase is an enzyme involved in the degradation of cytokinins, which are plant hormones that generally promote cell division, shoot growth, and delay senescence. Cytokinin oxidase breaks down cytokinins into inactive forms, thus reducing their concentration and activity in the plant.
Reducing the levels of active cytokinins through the over-expression of cytokinin oxidase would likely have the opposite effect on root growth. Cytokinins are known to have a negative effect on root development, as they tend to promote shoot growth at the expense of root growth. By decreasing the levels of cytokinins, root growth might be inhibited rather than promoted.
Therefore, over-expression of cytokinin oxidase would generally be expected to have a negative impact on root growth rather than a promoting effect
Hence, the correct answer is option 1.