Question

The response of different organisms to the environmental rhythms of light and darkness is called

(a) vernalization

(b) photoperiodism

(c) phototaxis

(d) phototropism.

Answer 1

Result: b) photoperiodism

Photoperiodism is the regulation of physiology and development of organisms in response to duration of light and darkness. For example flowering in plants in response to duration of light. Certain plants called short-day plants (eg. rice) flower when day light duration is less than certain threshold. On the other hand, plants called long day plants (eg. sugar beets) require long duration of light for flowering.

In phototropism, organism grows directionally in response to light, either towards light or away from light. For example, shoot growth towards light and root growth away from light.

Vernalization: Promotion of flowering or seed production in plants in response to prolonged exposure to low temperature

Phototaxis: Movement of organism in response to light either towards light (positive phototaxis) or away from light (negative phototaxis)