Question

Several horticultural techniques are followed for the production of bonsai plants. One of them is the drastic pruning of the root system. Which of the following physiological factors is involved in that method?
(a)Inadequacy of mineral nutrients
(b)Deficiency of auxins
(c)Impairment of water absorption
(d)Deficiency of cytokinins

Answer 1

Hint Root pruning is the process of cutting out long roots to encourage the growth of new roots closer to the trunk (common in potted plants). Tree root pruning is an essential step when an established tree or shrub is transplanted. This is mainly done to reduce stress in plants.

Complete answer:
Bonsai is a Japanese word for ' tray planting'. It is basically an art form in which several cultivation techniques are followed to produce small trees that mimic the shape and scale of full-size trees.
Roots in bonsai usually tend to 'colonize' an area or container. That means, they saturate the container with roots. In some cases, the roots might also even push the plant upwards from the container by the sheer volume of new roots. When this happens the plant is usually said to be root bound.
If root bound plants like bonsai are not top pruned they will quickly dry out on a hot and humid day and would require more than one watering per day. Problems related to water storage can be solved by top pruning as it will reduce the transpiration rate, but there will be additional problems if the plant is not also root pruned. For example, root pruning may damage a plant and therefore restricts its ability to take up water and nutrients. Additionally, only passive root pruning without top pruning will result in loss of food storage and weaker resultant top growth with small leaves and close internodes.

Additional information:
Advantages of root pruning:
-Root pruning is sometimes done to maintain a dwarfed size. If a dwarf tree increases in height rapidly, then root pruning will temporarily reduce the growth process which would be enough to stop growing tall and put all of its energy into growing new roots.
-Another advantage of root pruning is to encourage the flowering of a fruit tree or slow to bloom vine, such as wisteria. In this case, the plant will set flowers and seed, to propagate itself.
-Root pruning is also useful when potted plants have outgrown their container and cannot be moved to a larger one.
For good growth of the plant, trimming the roots back and repotting with some fresh soil will help keep the plant's growth in check.

So, the correct answer is 'Impairment of water absorption'

Notes: Root pruning must be done at times of the year that the stresses on the plant are minimal. For temperate climate plants, these conditions are optimal two times of the year, late fall and early spring. Tropical plants on the other hand can usually be root pruned and repotted during periods of 'quiescence' or slow growth.