Photosynthesis and Productivity of Soybean (Glycine max (L.) Merr.]

The peculiarities of leaf carbon dioxide gas exchange in soybean genotypes grown in field over a large
area and contrasting in duration of vegetation, photosynthetie traits and productivity were studied.
Varietal differences in the daily and ontogenetic changes in photosynthesis and photorespiration were
identified. It was established that the period of the high activity of photosynthetic apparatus in high
productive soybean genotypes lasts for a longer time. The photosynthetie rate and the rate of CO, re-
lease in light due to photorespiration are higher in high productive genotypes. The magnitude of plho-
torespiration in contrast soybean genotypes constitutes about 28-35% of photosynthetic rate. The ratio
between true photosynthesis and photorespiration in genotypes with different productivity is constant
enough during ontogenesis, indicating a direct positive correlation between true photosynthesis and
photorespiration.