Effects of Leaf Area on Photosynthetic Rate, Light Penetration, and Grain Yield in Barley1

Abstract

Related barley (Hordeum vulgare L.) lines, with small‐ and large‐leaf areas were developed and used to study the effect of leaf area on photosynthesis, light penetration, and grain yield. An infrared gas analyzer was used to measurep hotosynthesis of flag leaves in the laboratory and photosynthesis of plant canopies in the field. Light penetration into plant canopies was measured with tube solarimeters. LAI, grain yield, and the components of yield were determined in field plots.Photosynthetic rates per unit leaf area in the laboratory were similar in small and large flag leaves; thus, total photosynthetic activity per leaf was about twice as great in the large flag leaves. In field comparisons, however, no consistent differences in photosynthetic rates of small‐ and large‐leaf canopies could be detected, even though LAI's were greater in large‐ than in small‐leaf canopies by 19% in Population I and by 33% in Population II. Photosynthesis in the barley canopies as a whole was limited by lack of light throughout the entire range in intensity of solar radiation.In yield trials large‐leaf lines exceeded small‐leaf lines in flag leaf area by 70% and in LAI by 25%. Lines with small leaves produced more heads and higher grain yields than lines with large leaves when plants did not lodge. Where lodging occurred, however, large‐leaf lines had higher kernel weights and were higher yielding. We postulate that large leaves favor higher kernel weights and that small leaves favor production of more culms.