Intraraceme Competition in Field‐Grown Soybean¹

Abstract

Abscission probability for positions within a soybean [Glycine max(L.) Merr.] raceme may not be equal. The influence of the two most proximal pods on abscission probability and growth of remaining pods within a raceme was studied using the soybean cultivar ‘Williams’. Plants were field grown (1982, Beltsville silt loam, Typic Fragiudult; 1983, Mattapeake silt loam, Typic Hapludult). Treatment consisted of removing or not removing the two most proximal (raceme Positions 1 and 2) pods. More flowers were produced at Node 8 than at either Node 10 or 12. Abscission probabilities for Positions 1, 2, 3, 4, and 5 of untreated racemes were 4, 10, 56, 77, and 99%. Removal of proximal pods decreased the abscission probability at Position 3 in five out of six instances (Nodes 8, 10, 1982; Nodes 8,10, and 12,1983) and at Position 4 in four of six instances (Node 8, 1982; Nodes 8, 10, and 12, 1983), but usually did not increase individual pod or seed weights. In most instances, individual pod and seed weights were smaller at Position 4 than at Position 1. The presence of proximal pods on soybean racemes interfered with the development of distal pods and increased the abscission probability of reproductive structures borne at distal positions.

Accelerating yield potential in soybean: potential targets for biotechnological improvement

“…Egli & Bruening (2002) hypothesized that competition for assimilate from early developing pods is a main factor in flower and pod abortion. This is based on their findings that flowering in soybean follows a bi‐modal distribution, with 100% pod survival in the first cohort and <60% in the second, which is consistent with previous reports (Huff & Dybing 1980; Spollen, Wiebold & Glenn 1986). The asynchronous and extended duration (>30 days) of flowering in soybean was identified as a possible cause of late‐flower abortion, as the large sink strength of fast‐growing pods that were initiated early would demand preference for available photoassimilate and lead to shedding of less‐developed pods.…”

Flower Abortion Caused by Preanthesis Water Deficit Is Not Attributed to Impairment of Pollen in Soybean

“…The magnitude of abortion varies with the position on the plant, being greater in the branches, the lower part of the main stem and the top nodes of the main stem (Hansen and Shibles, 1978; Wiebold et al, 1981; Gai et al, 1984; Heindl and Brun, 1984). Within individual racemes, the proximal positions exhibit a higher pod‐set percentage than do the distal positions (Huff and Dybing, 1980; Dybing et al, 1986; Spollen et al, 1986a; Carlson et al, 1987; Wiebold, 1990; Wiebold and Panciera, 1990; Kokubun and Honda, 2000). The physiological mechanism controlling reproductive abortion, however, remains unclear.…”

Flower abscission in soybean as affected by assimilate supply and hormone levels

“…It is thought that ABA may stimulate the increased production of invertase resulting in more glucose for the growing pod. Conversely, Spollen et al (1986) found no changes in ABA levels when pod survival was increased in distal pods of a raceme, by the removal of proximal pods.…”