Kinetic Study on the Development of the Capacity to Accumulate Chlorophyll <italic>A</italic> without a Lag Phase during Continuous Far-Red Irradiation in <italic>Pharbitis nil</italic> Seedlings

Abstract

To analyze how the capacity to accumulate chlorophyll a (Chi a) without a lag phase develops by continuous far-red light (FR) irradiation, the time course of the capacity was investigated under various FR-dark conditions in Pharbitis seedlings. The capacity, which is negligible in darkness, rapidly developed on transfer to continuous FR irrespective of the age of the seedlings, the maximum level being attained about 18-24 h after the onset of.FR irradiation. The-capacity gradually decreased thereafter whether in darkness or under extended FR irradiation. When the seedlings pretreated by 6-12 h of FR followed by 66-60 h darkness (which have no capacity) were exposed to the second FR irradiation for up to 72 h, the level of the capacity acquired during the second FR irradiation was the lower the higher the level acquired by the first FR irradiation. A possible mechanism which determines the time course of the development of the capacity is discussed.