TRANSPORT OF ASSIMILATE INTO THE SOYBEAN FRUIT AND SEED GROWTH

GARY MICHAEL FADER, Purdue University

Abstract

Relationships between the amount of carbohydrate imported by the soybean {Glycine max (L.) Merrill} fruit, metabolic status of the tissues involved in the transport of assimilate into the fruit, fruit respiration, and seed growth were evaluated. Plants at mid pod-fill were subjected to various light intensities or CO(,2) concentrations to alter the amounts of assimilate available to the fruit. The amount of carbohydrate imported by the fruit, fruit respiration, dry matter accumulation rates of seeds, along with glucose, sucrose, and starch concentrations, adenylate energy charge (AEC), and total adenylate pool ((SIGMA)AdN) in the pod wall, seed coat, and cotyledons were determined for three-seeded fruits located from nodes 6 to 10. The concentration of sucrose remained constant in the pod wall (1.0 mg(.)100 mg dry wt('-1)), seed coat (6.5 mg(.)100 mg dry wt('-1)), and cotyledons (4.5 mg(.)100 mg dry wt('-1)) at moderate and high TC respiration rates, and dry matter accumulation rates of seeds. Furthermore, AEC remained relatively constant in the pod wall (0.55), seed coat (0.24) and cotyledons (0.44) with changes in fruit respiration. This suggests that the amount of sucrose transported to the fruit, and its flux through the sucrose pools of the fruit, was more important to seed growth and fruit respiration than pool size. The average (SIGMA)AdN in the seed coat (1300 (rho)moles(.)mg dry wt('-1)). In addition the (SIGMA)AdN and its increase with increased respiration rate in the send coat suggest an energy dependent process is involved in the transport of sucrose through the seed coat. Starch concentration in the pod wall decreased as TC decreased to low values. However, remobilization of starch only occurred when the assimiliate imported by the fruit could not maintain the sucrose pool of the pod wall.

Degree

Ph.D.

Subject Area

Agronomy

COinS