Regulation of enzyme levels by phytochrome in mustard cotyledons: Multiple mechanisms?

摘要: Phytochrome controls the appearance of many enzymes in mustard (Sinapis alba L.) cotyledons. The problem has been whether effect phytochrome on this organ is due to a common initial action Pfr, e.g. liberation "second messenger". We have compared modulation by light (phytochrome) phenylalanine ammonia lyase (PAL)(+) and ribulosebisphosphate carboxylase (Carboxylase)(+). PAL becomes detectable cotyledons at 27 h after sowing while Carboxylase starts appear only 42 (starting points, 25° C). starting points cannot be shifted light. As major result, case inductive continuous red (given from time sowing) remains fully reversible 756 nm-light up point (27 with full reversibility lost approximately 15 sowing. While induction already saturated very low level Pfr (e.g. saturates response) does not depend irradiance 675 mW m(-2) 67.5 lead same course), graded response over wide range doses depends strongly fluence rate (high response, HIR). It concluded that are separated but differ every regard except both responses mediated phytochrome.The present data support previous conclusion specification temporal spatial pattern development independent even though realization can occur presence (Pfr). seems there no feedback specification.