Characteristics of Reproductive Abortion in Soybean1

Abstract

The abortion of reproductive plant parts is an important, but not well understood, part of the yield production process in many crop plants. The objective of this research was to characterize the effects of growth stage and timing on the abortion process of soybean [Glycine max (L.) Merr.] flowers exhibiting variation in abortion. Soybean plants were grown in a greenhouse (cv. McCall) and for 3 yrs in the field (cv. Kent). The soil types were a Donerail silt loam (Typic Arguidofl), Maury silt loam (Typic Paleudalf), and a Lanton silt loam (Cumulic Haplaquolls). Fully‐opened flowers located on nodes from the middle of the main stem were marked during early (R1) and late (R3) flowering and then observed for 2 or 3 weeks to determine the extent and timing of flower abortion. Defoliation and three different depodding treatments were used to alter abortion. Nineteen percent of the early flowers aborted (failed to produce seed bearing pod) in the greenhouse, but 31 to 48% aborted over yrs in the field. Abortion of late flowers varied from 76 to 92% in two greenhouse experiments and from 69 to 90% in the three field experiments. The abortion process occurred more rapidly in the greenhouse where much of the abortion was apparent by 6 days after flower opening (DAFO), compared with the field where less than 50% of the abortion was apparent by 10 DAFO. The three depodding treatments decreased and defoliation increased flower abortion. Removing all pods from a plant except those at one node, reduced late flower abortion at that node from 69 to 54%. However, removing all pods from only one node of the plant reduced abortion at that node from 69 to 36%. The results of these experiments suggest that the processes controlling abortion operate at the individual node level and that the whole plant source‐sink ratio is of secondary importance.