Influence of photoperiod and water supply on production of seed and dry matter in three varieties of soybean, Glycine max (L.) Merr.

In glasshouse experiments soyabeans cv. Improved Pelican, L.Z. and Pennsoy were grown at 30/20 deg C day/night temperatures and under the prevailing natural photoperiod (16.2, 14.2 and 12.7 h in July, Aug. and Sept., respectively) or a controlled 12-h photoperiod. Plants were given 25, 50, 75 or 100% of a standard water application. In a further laboratory experiment, rates of photosynthesis and transpiration were determined under different light intensities. DM production, seed production, water consumption and the rate of photosynthesis did not differ between cv. and there was a rectilinear relationship between seed production and DM production and between DM production and water consumption. Plants given a >12-h daylength did not flower. In the controlled 12-h daylength, productivity/unit of water consumption was smaller than in the prevailing daylength. The rate of photosynthesis was somewhat lower than the rate presented by de Wit for most agricultural crops and the relationship between the rate of photosynthesis and transpiration was curvilinear for short periods. (Abstract retrieved from CAB Abstracts by CABI’s permission