Effect of carbon dioxide enrichment on chlorophyll content, starch content and starch grain structure in Trifolium subterraneum leaves

Abstract

Trifolium subterraneum (cv. Dinninup) responds to enriched atmospheric CO 2 in a manner similar to that described by Madsen (1968 and 1976) for tomato. In immature leaves, the total chlorophyll content per unit dry weight and the chlorophyll a:b ratio are significantly lower in plants grown at 0.10 vol% CO 2 . Although fully expanded mature leaves partially overcome the deficit in chlorophyll content, the chlorophyll a:b ratio remains substantially lower in these high CO 2 grown plants. The large amount of starch accumulated as irregularly shaped grains appears to disrupt normal chloroplast structure in clover plants grown in enriched atmospheric CO 2 . These results indicate the chlorotic appearance of leaves from high CO 2 grown clover plants is due to a decrease in chlorophyll content per dry weight possibly resulting from large starch grains and starch accumulation altering normal chloroplast structure and function.