Low Temperature Development under Intermittent Light Conditions Results in the Formation of Etiochloroplasts

Abstract

Summary The effects of developmental temperature on etioplast to chloroplast conversion were examined in winter rye ( Secale cereale L. cv. Muskateer) upon exposure to intermittent light. One cycle of intermittent light is defined as exposure to 2 min of incandescent light (10 µE m- 2 ·s -1 ) followed by 118 min of darkness. Although 5 °C intermittent light seedlings developed almost 2-fold higher chlorophyll levels after 48 to 80 cycles than 20 °C seedlings, both exhibited similar maximum photosystem I activities. Development of maximum photosystem I and photosystem II activity was delayed at 5 °C relative to that observed at 20 °C. Etiolated seedlings exposed to 48 cycles of intermittent light at 20 °C exhibited the normal light-dependent breakdown of prolamellar bodies and protochlorophyllide oxidoreductase followed by the appearance of thylakoid membranes. In contrast, the plastids developed at 5 °C appeared to be etiochloroplasts which exhibited prolamellar bodies, high levels of protochlorophyllide reductase in addition to thylakoid membranes. We suggest that during chloroplast biogenesis intermittent light at low developmental temperature inhibits the plastid proteases involved in the light-dependent breakdown of protochlorophyllide reductase.