LIGHT AND SOME PLANT RESPONSES*
We have long known that plants are influenced by light in many different ways. For example, the seasonal change in daily duration of light controls flowering of many species, some flowering only when days are short and others only when days are long. Daylength also determines the time of year at which many trees and shrubs cease expansion of new leaves and produce resting buds before the onset of winter. Light is required by some seeds for germination, but it prevents the germination of others. It regulates elongation of stems of some plants and promotes coloration of the ripening fruits of others. It enters into the regulation of growth and development of plants in countless ways that are familiar to us and probably in many others that have not yet come to our attention.
In the last 4 or 5 years we have learned that a number of these seemingly unrelated responses of plants to light have some points in common. Several of them are, in fact, controlled by the same basic light reaction.
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