Partial Restoration of the High Rate of Plastid Pigment Development and the Ultrastructure of Plastids in Detached Water-stressed Wheat Leaves

Abstract

Detached etiolated wheat (Triticum aestivum L. cv. Chris) leaves accumulated plastid pigments at a high rate, developed chloroplasts with stacked thylakoids, and stored plastid starch when wetted on filter paper in light. A moderate water deficit of - 10 bars markedly reduced the accumulation of chlorophyll and carotenoids in the 8-day-old detached leaves during greening. delta-Aminolevulinic acid treatment of stressed leaf segments resulted in slightly increased pigment accumulations but benzyladenine application restored plastid pigment formation in stressed tissue to within 15% of the pigment content of the nonstressed detached leaves. The addition of delta-aminolevulinic acid to benzyladenine-treated stressed leaf segments improved both chlorophyll and carotenoid formation to nearly the amounts found in nonstressed leaf tissue. Stressed leaf sections developed plastids that were small, lacked starch, contained few thylakoids per granum, and possessed dilated thylakoids. Benzyladenine application to the stressed leaf segments did not restore normal plastid stacking but benzyladenine induced the formation of extended intergranal lamellae and stimulated pigment accumulations in both stressed and nonstressed detached leaves. Starch was absent in plastids of benzyladeninetreated leaf sections.