Question

Richmond-Lang effect is shown by
A. Auxins
B. Sugars
C. Kinetin
D. Gibberellins

Answer 1

Hint: Richmond and Lang were the scientists that discovered this effect in 1967. Cytokinins regulate cell division and delay of senescence, Auxins stimulate the elongation of stem and development of lateral buds and Gibberellins is responsible for seed germination and flowering etc.

Complete answer:
The Richard-Lang effect was discovered in 1967 by Richmond and Lang. According to this effect, the lag of senescence of the leaves and other parts of the plants that occur with the help of application of plant growth regulator cytokinin.
Kinetin is a type of phyto hormone called cytokinin that influences the development, plant growth and physiology that includes chloroplast differentiation and delay of senescence.
Senescence is a biological ageing that involves the gradual deterioration of the functional characteristics. It is a cellular response that is characterised by the stable growth arrest of the plant cell.
The stimulation of cell division by the cytokinin phytohormone can delay plant senescence. This phytohormone prohibits the damage of chlorophyll and the parts of plants do not change into yellow. Hence the effect is called Richmond Lang effect. The lag of senescence of distinct portions and leaves happens with the support of plant development controller cytokinin.
Retarding senescence leads to the delay of chlorophyll degradation rate, yellowing colour of the leaves and keeping it active for a longer time.
It influences the synthesis of protein and minerals and also mobilizes the nutrients. The hormone causes the delay in the process of senescence and aging.

Hence, the correct answer is option (C).

Note: In the Richmond Lang effect, there is a prevention of degradation of proteins and immobilisation of the nutrients. The molecules that include chlorophyll pigments in the plant are not degraded. This helps in prevention of aging and falling of the plant leaves.