Question

Etiolated plants are formed due to a lack of
(a)Light
(b)Hg
(c)Fe
(d)Mg

Answer 1

The plant needs many factors in order to survive and carry out its life functions. Etiolation of a plant is the elongation and weakening of the plant stem and development of yellowish-white color in its leaves.

Complete answer:
In absence of light etiolation of plants occurs which causes the stems to become weak, smaller leaves, and a pale yellow coloration of the plant. In that case, the plant is said to be etiolated.

Additional Information: Etiolation occurs due to the absence of light and in this condition, if a seedling is grown, it is known as skotomorphogenesis and leads to an etiolated seedling. It leads to excessive elongation of the stem towards the source of light which makes the plant weak and develops longer internodes which result in smaller leaves. The color of the plant turns yellowish-white which is known as chlorosis. The chloroplasts which do not get light are known as etioplasts.
Lack of iron in plants may cause interveinal chlorosis which is the development of yellow leaf with a network of dark green veins. This happens because iron is necessary to produce chlorophyll. Lack of iron may happen because of waterlogging and overfertilization.
Magnesium deficiency causes degradation of chlorophyll in the old leaves and interveinal chlorosis.
Mercury contamination causes abnormal germination and inhibits photosynthesis.
So, the correct answer is ‘Light’.

Note: De-etiolation occurs after etiolation and it is the reverse process, therefore known as greening. This is a physiological and biochemical process of a plant shoot to emerge from the ground, or in response to light after etiolation. The changes seen in plants during de-etiolation are inhibition of hypocotyl lengthening, stimulation of the cotyledon expansion, synthesis of anthocyanin, and chloroplasts development from etioplasts.