Calcium and phytochrome control of leaf unrolling in dark-grown barley seedlings

✍ Scribed by Neil Viner; Garry Whitelam; Harry Smith

• Book ID: 104753048
• Publisher: Springer-Verlag
• Year: 1988
• Tongue: English
• Weight: 425 KB
• Volume: 175
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00392429

✦ Synopsis

The red light-stimulated component of unrolling in sections from 7-d-old dark-grown barley (Hordeum vulgare L.) leaves is inhibited by ethyleneglycol-bis-(fl-aminoethyl ether)-N,N,N',N'tetracetic acid (EGTA). A free-Ca 2+ activity of less than 40 gM restores the ability to respond to red light, but only if supplied within 1 h of red light. Magnesium ions are an ineffective substitute. At least two processes in unrolling appear to be Ca 2 +-sensitive.

Fluence-response measurements indicate that the levels of the far-red-absorbing form of phytochrome (Pfr) still present 4 h after red-light treatment should be above saturation for the unrolling response; consequently, loss of Pfr does not explain the loss in effectiveness of Ca 2 + during prolonged EGTA treatment. However, if a further red-light treatment is given simultaneously with Ca z+ addition 4 h after the initial light stimulus, then full unrolling occurs in EGTA-treated sections. These data indicate that, under normal circumstances, a functional change in the properties of Pfr must occur, uncoupling it from the transduction chain.