Shade Induced Changes in Flower and Pod Number and Flower and Fruit Abscission in Soybean

Abstract

Seed number per unit area is important in determining yield in soybean [Glycine max (L.) Merr.]. Field and greenhouse experiments were conducted to evaluate the role of flowers per plant and flower and fruit abscission in determining pod and seed numbers. Two greenhouse experiments were conducted with the McCall cultivar [Maturity Group (MG) 00] and four cultivars [McCall, Hardin (MG I), Harper (MG III), Essex (MG V)] were used in field experiments in 1989 and 1990. The field experiments used either 0.38‐m (McCall and Hardin) or 0.76‐m rows (Harper and Essex) with a constant seeding rate of 26 seeds per meter. Shade cloth (63% in the greenhouse and 30 and 63% in the field) was placed over plants from R1 to maturity. Additional treatments in the greenhouse included shade from R1 to R4, R4 to R5, R5 to R6, and R4 to R8. Plants were harvested at maturity and flower and pod abscission was determined by counting both the scars marking the point of attachment of flowers and pods, and mature pods. Shade reduced pod numbers and the reductions were due to both increased flower and pod abscission and fewer flowers per plant. Both the number of nodes on the main stem and flowers per node were affected by the shade. Shade during any part of the R1 to R6 period reduced pod numbers in the greenhouse. These data indicate that environmentally induced variation in pod numbers in soybean is a result of both changes in flower and fruit abscission and the number of flowers produced.

Roles of Auxin and Cytokinin in Soybean Pod Setting

“…Soybean plants differentiate abundant floral buds, but a large proportion of them abort during development (Kato, 1964;Abernethy et al, 1977): under normal conditions, pod set percentage is only 20 to 40% (Wiebold et al, 1981;Antos and Wiebold, 1984;Jiang and Egli, 1993). By reducing this abortion, it might be possible to increase the pod number, thereby increasing the yield (Kokubun, 2004).…”

Effects of Source/Sink Ratio and Cytokinin Application on Pod Set in Soybean

“…Under normal growing conditions, pod set percentage ranges from 20 to 40% (Wiebold et al, 1981;Jiang and Egli, 1993). By reducing this abortion, we might be able to increase pod and seed numbers, thereby increasing the yield (Kokubun, 2004).…”

The shoot dry matter accumulation and vertical distribution of soybean yield or yield components in response to light enrichment and shading

“…Enhanced the effectiveness of the soybean leaf photosynthesis under light enrichment is resulting in rapid shoot dry matter accumulation. However shading reduced source of leaf canopy photosynthesis, and decreased under-ground plant dry matter weight (Jiang and Egli, 1993).…”

“…Mathew et al (2000) analyzed the effects of different light-enriched treatment time on soybean yield components and indicated that there are different responses of seed yield to light enrichment started at late vegetative and early pod formation. However, reducing of light intensity through shade will increase young pods or flowers abscission, lengthen internodes of soybean plant, decrease seed yield and increase plant lodging (Ephrath et al, 1993;Jiang and Egli, 1993;Li et al, 2006). Jiang and Egli (1995) stated that duration of shading also was an important factor influencing soybean yield.…”