The effect of leaf age on the photosynthetic rate of themeda triandra forsk¹

Abstract

The apparent photosynthesis of progressively older leaves of Themeda triandra was recorded in a controlled environment by means of gas exchange measurements. Photosynthetic rate increased with increasing leaf age and was maximal in the third fully expanded leaf. Thereafter, photosynthesis dropped sharply, but the photosynthetic rate of the oldest green leaf was still 55 % of that of the most efficient leaf. The implication is that old green leaves can probably still play an important role in initiating regrowth after defoliation of younger leaves.