Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 19, 1996
Publication Date: N/A
Interpretive Summary: Soybean currently grown in North America often experience short-term cold temperatures during early growing season. As soybean production is expanding to northern latitudes and high altitudes, cold temperature, particularly periodic short-term cold temperatures could be deleterious to soybean growth and production. Little is known about the extent of damage that occurs, or the nature of the injury that may be caused by low, but not freezing temperatures. Our results showed that 24 hours of 8 degrees C cold temperatures imposed at early growing season and early flowering stages did not significantly affect the early vegetative growth of soybean, but delayed flowering by up to 7 days. The delays in flowering may partially result from decreased leaf photosynthesis and favored vegetative growth over reproductive growth in cold-injured plants. The results will be incorporated in the soybean simulation model which is being used as a management-aid at the farm level.
Technical Abstract: Soybean seedlings often experience short-term cold temperature early in the growing season that may affect soybean subsequent growth. The objective of this study was to evaluate the effects of short-term cold temperature on soybean (Glycin max [L.] Merr. 'Hutcheson') growth, flowering, dry matter partitioning, carbohydrate content, and photosynthesis. Soybean plants were grown in controlled environmental conditions at a range of temperatures and treated with a 8 C for 24 h at V5 and R1 stages. The two cycles of cold temperatures decreased plant dry weight and reduced the partitioning of dry matter into pods for plants grown in day/night temperatures of 23/18, 28/23, or 33/28 C. However, the cold treatments did not affect the number of main stem nodes. The cold treatments delayed R1 for plants grown at 28/23 C, delayed R2 for plants grown at all three temperatures by up to 7 days, and prolonged the time periods between R1 and R2. Leaf photosynthesis was lower in the treated plants than in the control plants at 5h after the treatment and recovered 24h after the growing temperatures were restored. Soluble carbohydrate in leaves was reduced by the short-term cold temperature 5h after the growing temperatures were restored, but these carbohydrate values recovered or increased after photosynthesis had recovered. Our results indicate that cold temperature injury delayed soybean reproductive stages and that the delays may be to some extent attributed to decreased leaf photosynthesis and soluble carbohydrate, and altered dry matter partitioning between vegetative and reproductive growth. The effects of short-term cold temperatures varied, with a greater effect on plants grown at 28/23 C, a near optimum temperature for early dry matter production.