Theses and Dissertations

Issuing Body

Mississippi State University


Reddy, K. Raja

Committee Member

Irby, J. Trenton

Committee Member

Phillips, J. Mike

Committee Member

Henry, W. Brien

Committee Member

Shankle, Mark W.

Date of Degree


Document Type

Dissertation - Open Access


Plant Science (Agronomy)

Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Temperature is a major factor affecting plant growth and development at all stages. The objectives of this study were to investigate the temperature effects on all aspects of soybean growth and development. Five experiments were conducted at a wide range of temperatures under optimum water and nutrient conditions at specific growth stages. Two cultivars, Asgrow AG5332 (AG) and Progeny P5333RY (PR) from MG V with different growth habits, were used. All studies except the seed germination were conducted in sunlit plant growth chambers under optimum water and nutrient conditions. The seed germination experiment was conducted in a temperature-controlled incubator. Germination traits were measured during seed germination studies. In other experiments, plant growth, developmental rates, gas exchange parameters, and seed yield and quality were measured. Cultivars did not differ for seed germination and emergence traits. Quadratic functions best described time to 50% germination seed germination and emergence rates. The three cardinal temperatures for seed germination were 8.56°C (base) 27. 96°C (optimum) and 46.92°C (maximum). The base and optimum temperature for seed emergence were 10.6 and 36.7°C, respectively. During the early-season, 0-21 days, root and shoot growth parameters responded similar temperature responses, the root traits have a lower optimum (29.91°C) than the shoot parameters (36.56°C). Cultivars varied in their response to temperature during vegetative development, particularly for growth parameters, and the temperature optimums for various parameters. Node addition rate was not different among the cultivars but increased with increase in temperature. The flowering time (R1) from emergence showed quadratic trends with an increase in temperature up to 28°C and increased slightly at the higher temperatures. The PR cultivar, on an average, took 15 additional days to reach flowering compared AG cultivar across temperatures. Pod and seed yield and individual seed weight and harvest indices showed quadratic trends with maximum values at 25.82 °C for AG and 23.36 °C for PR. The functional algorithms could be helpful for management and in improving crop models.



Soybean||Temperature||root growth||photosynthesis||seed yield||growth and development