Nutrients‐mediated shift in temporal expression of phytochrome controlled β‐amylase synthesis in mustard (Sinapis alba L.) cotyledons

Abstract

Abstract. In cotyledons of mustard (Sinapis alba L.) seedlings grown with distilled water (DW) phytochrome controlled increase in β‐amylase (E.C. 3.2.1.2) level takes place at about 42 h after sowing (starting point), while the photoresponse escapes from photoreversibility at 30 h after sowing. The temporal onset of starting point is presumed to be determined by innate process of developmental homeostasis, which is not amenable to influence of environmental factors such as light and nutrients. However, the temporal appearance of onset of phytochrome controlled increase in β‐amylase level (starting point) in seedlings grown with Hoagland's nutrient solution (HS) is delayed by 9 h as compared to DW‐grown seedlings. Concomitantly, the temporal appearance of the loss of photoreversibility of phytochrome mediated increase in β‐amylase level (coupling point) is also delayed by 9 h in HS‐grown seedlings. HS does not influence the primary action of phytochrome, the lifetime of components involved in signal chain of above photoresponse and the turnover of β‐amylase enzyme. These results indicate that HS‐induced temporal shift in onset of starting point of above photoresponse is caused by interaction of nutrients with the process of developmental homeostasis. Copyright © 1985, Wiley Blackwell. All rights reserved