Effects of light and growth regulators on the reversibility of the senescence in attached leaves of barley.

Abstract

Senescence of intact barley seedlings (Hordeum vulgare) judged by the loss of chlorophyll, was induced by putting them in the dark. Reversal of senescence by application of light was also observed. The chlorophyll content recovered after two days in the light, but seedlings were unable to recover their initial level of pigment after four days in the dark, This suggests the onset of an irreversible stage in senescence from the fourth day. Supply of kinetin to the leaf after two or four days in the dark induces a slight increase in chlorophyll content. Whereas reversion of the senescence is obtained immediately after the dark period, the same treatment with abscisic acid accelerates the loss of chlorophylls and retards the reversion by light treatment.