Question

Shredding of leaves, flowers and fruits due to change in hormone balance in plants is-
A. Senescence
B. Abscission
C. Photoperiodism
D. Vernalisation

Answer 1

Hint: The process of shredding leaves, fruits and flowers does not involve dying of cells. Furthermore, shredding of the plant part is a common process and does not result in death of a plant. Most of the plants undergo this process to conserve the nutrients for survival or to secure themselves from any possible infections. It’s a process that is regulated by hormones like auxin, ethylene and abscisic acid.

Complete answer:
Shredding of leaves or flowers and fruits is an effect known as Abscission. This effect takes place in plants as a result of hormonal interaction. Shredding of a plant part takes place because either the plant does not need that part anymore (to conserve the nutrients for the whole plant) or because that part of plant has been damaged. For example- due to gall infection at leaves, the leaves that are damaged by the infection get detached by the plant as a measure of protection from further spread of the infection.
The fruits which are not fully ripened are detached from the plant and leaves are shed during autumn and the start of winter so as to conserve the nutrients, mainly, nitrogen, because it is required by the plant to make amino acids, proteins, etc.

Abscission takes place with three main steps- resorption, protective layer formation and detachment. Mainly auxin and ethylene play a significant role in this process. When the supply of auxin decreases to a certain part of the plant, the abscission zone becomes prone to the effect of ethylene. Ethylene stimulates the release of cell wall degrading enzymes, for example- polygalacturonase which further dissolves the cell wall of the abscission zone and finally the plant part detaches from the plant.

Senescence is the process in which a cell stops dividing and is arrested at that stage. However, the cell does not die. Senescence is also called as ageing in common language. Senescence of the cells of an individual might lead to the death of the whole organism.

Photoperiodism is the process in which plants show physical responses to the exposure of light to it. Some plants flower in accordance to the amount of light they get or get exposed to.

Vernalisation is a whole different process of inducing a plant to flower by exposing it to low temperature for a prolonged amount of time.

Hence, the correct answer is option (B).
Note: Senescence is a process which results in death of an organism because slowly when all cells stop dividing and stops processing their functions; the organism will eventually face death. But in abscission, the plant does not die. Abscission is a process which is adopted by a lot of plants such as deciduous plants. Those plants shed their leaves before winter to conserve the water evaporation and to keep the nutrients stored for the future usage by the plant.