Chlorosis in a Tree Fern (Cyathea cooperi) Induced by Brief Heat Stress

Abstract

Chlorosis occurred in a frond of Cyathea cooperi (Hook. ex F. Muell.) Domin exposed briefly to air temperatures up to 41.2°C during expansion. Pinnule anatomy and cellular organization were generally unaffected, but chloroplast development was impaired. Chlorophyll concentration was reduced to less than 5% of normal, and grana were few in number and attenuated. Stroma thylakoids were almost completely absent, starch grains did not develop and membrane-bound vesicles were numerous and sometimes large. Previously matured fronds were not injured visibly by high temperatures.