Translocation Pattern of Soybeans as Affected by Growth Substances and Maturity1

Abstract

‘Chippewa’ soybeans (Glycine max L. Merr.) were planted in 38 cm rows, 8 cm apart within the row in 1968 and 1969. Two growth substances, 2‐chloroethylphosphonic acid (Echrel) and N‐dimethylamine succinamic acid (Alar), were applied at the third trifoliolate leaf stage. Specific leaves of treated and non‐treated plants were fed 50 µc of 14CO2 for 5 min at four stages of maturity. Plants were harvested at 1/2 hour to one week after feeding, and radioactivity in plant parts was determined. Maturity affected translocation more than did growth substances. There were two distinct patterns of translocation. The first occurred before pods started to fill and was characterized by non‐specific transport to meristematic regions above the fed leaf. Translocation during rapid pod filling was primarily to pods at the axil of the fed leaf and at the second axil below the fed leaf. As plants approached maturity, a greater proportion of the total assimilate was translocated from the fed leaf. Growth substances did not affect the translocation pattern of soybeans. However, plants treated with Ethrel transported more 14C photosynthate to pods at the axil of the fed leaf.