Soybean Reproductive Sink Size and Short‐term Reductions in Photosynthesis during Flowering and Pod Set

Egli, D. B.

doi:10.2135/cropsci2009.09.0518

Cited by 44 publications

(28 citation statements)

References 33 publications

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“…On the other hand, at higher densities, photosynthetic rates per plant were lower, as were nitrogen fixation inputs per plant. These results are consistent with studies of photosynthetic rate reduction, in which manipulations of the source, such as shading and defoliation, resulted in reductions in the number and dry weight of grains per plant (Egli, 2010;Proulx and Naeve, 2009). Additionally, with decreases in the supply of photosynthates (source) caused by the same treatments there were decreases in the rates of nitrogen fixation (Neves and Hungria, 1987).…”

Section: Discussionsupporting

confidence: 89%

Plant densities and modulation of symbiotic nitrogen fixation in soybean

Luca

Hungría²

2014

Sci. agric. (Piracicaba, Braz.)

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Soybean nitrogen (N) demands can be supplied to a large extent via biological nitrogen fixation, but the mechanisms of source/sink regulating photosynthesis/nitrogen fixation in high yielding cultivars and current crop management arrangements need to be investigated.We investigated the modulation of symbiotic nitrogen fixation in soybean [Glycine max (L.) Merrill] at different plant densities. A field trial was performed in southern Brazil with six treatments, including non-inoculated controls without and with N-fertilizer, both at a density of 320,000 plants ha −1 , and plants inoculated with Bradyrhizobium elkanii at four densities, ranging from 40,000 to 320,000 plants ha −1 . Differences in nodulation, biomass production, N accumulation and partition were observed at stage R5, but not at stage V4, indicating that quantitative and qualitative factors (such as sunlight infrared/red ratio) assume increasing importance during the later stages of plant growth. Decreases in density in the inoculated treatments stimulated photosynthesis and nitrogen fixation per plant. Similar yields were obtained at the different plant densities, with decreases only at the very low density level of 40,000 plants ha −1 , which was also the only treatment to show differences in seed protein and oil contents. Results confirm a fine tuning of the mechanisms of source/sink, photosynthesis/nitrogen fixation under lower plant densities. Higher photosynthesis and nitrogen fixation rates are capable of sustaining increased plant growth.

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Section: Discussionsupporting

confidence: 89%

Plant densities and modulation of symbiotic nitrogen fixation in soybean

Luca

Hungría²

2014

Sci. agric. (Piracicaba, Braz.)

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“…In this study, individual seed weight and seed number per pod were also not affected by [CO 2 ] enrichment, suggesting that the increase in seed weight with elevated [CO 2 ] was mainly caused by an increase in the number of pods and seeds produced by the greater number of nodes per plant. Seed numbers produced by soybean are also related to canopy photosynthesis during the early reproductive stage (Kokubun and Watanabe, 1981;Egli, 2010). Sameshima (2000) reported that seed number per soybean plant was positively affected by the dry matter production rate during the exponential seed growth phase.…”

Section: [Co 2 ] Effects On Seed Weight Seed [N] and Their Related mentioning

confidence: 99%

Effects of elevated CO2 concentration and temperature on seed production and nitrogen concentration in soybean (Glycine max (L.) Merr.)

Kumagai

Tacarindua

Homma

et al. 2012

J. Agric. Meteorol.

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The effects of elevated carbon dioxide concentration ([CO 2 ]) and temperature and their interactions on leaf photosynthesis, reproductive processes, seed weight and seed nitrogen concentration ([N]) of soybeans (Glycine max (L.) Merr.) were investigated using temperature gradient chambers. Plants were grown under four regimes comprising two levels of [CO 2 ], ambient (LC) and ambient＋ 200 μmol mol -1 (HC), and two levels of temperature, low (LT) and high (HT, LT＋～3℃). Plant and seed weights were significantly increased by elevated [CO 2 ] in both temperature regimes. Increased seed weight under elevated [CO 2 ] was mainly because of the production of more nodes and seeds per plant. Increased temperature significantly increased the number of seeds per plant but decreased individual seed weight in both [CO 2 ] regimes. Increased temperature therefore had no effect on seed weight. The increased seed number per plant in the HT regimes resulted from increased pod numbers per node. The light-saturated photosynthetic rate increased with increasing [CO 2 ] and temperature, presumably resulting in more seeds per plant. The reduction in individual seed weight with increased temperature was attributed mainly to lower individual seed growth rate and fewer cotyledon cells per seed. The reduction in individual seed weight with increased temperature was less pronounced in the HC regime than in the LC regime, and there was a significant interaction between [CO 2 ] and temperature. However, there was no interaction between [CO 2 ] and temperature for seed weight. Neither individual effects nor interaction of [CO 2 ] and temperature were observed for seed [N]. This study raises the possibility that projected increases in atmospheric [CO 2 ] during the 21st century will increase the yield of soybeans without decreasing seed [N] in regions that have near or below optimum temperatures (near 25℃ or above) for soybean yield.

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“…On the other hand, pods and seeds per unit area are associated with canopy photosynthesis or crop growth rate during flowering and pod set (growth stage R1-R5; Fehr and Caviness, 1977) (Schou et al, 1978;Jiang and Egli, 1993;Board and Tan, 1995;Egli, 2010). This association, coupled with the relatively high…”

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confidence: 99%

The Relationship between the Number of Nodes and Pods in Soybean Communities

Egli

2013

Crop Science

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Soybean [Glycine max (L.) Merr.] yield is often associated with the number of pods per unit area, which can be construed to suggest that the number of pod bearing structures (nodes) plays a role in determining yield. This hypothesis was tested in a 2‐yr field experiment at Lexington, KY (38° N latitude). Four cultivars that varied in relative maturity (0.7 to 5.3) and high and low populations (one cultivar) were used to create variation in nodes per square meter. The experiments were planted on 25 May 2010 and 31 May 2011 in 38‐cm rows (19 cm for the high population) and the target populations were approximately 43 (four cultivars), 26 (low population), and 78 (high) plants m−2. Irrigation was used to minimize water stress. There were four replications of each treatment in a randomized complete block design. A 30‐cm section of bordered row was harvested at maturity to determine flower scars, pods, and nodes. The photosynthetically active radiation interception was roughly 90% or above at R1 for all treatments and there was little difference in incident solar radiation or temperature among treatments during flowering and pod set. There was a two‐fold variation in nodes per square meter in both years. Pods per square meter increased in concert with nodes per square meter up to approximately 70% of the maximum node number; above that level there was no change in pods per square meter. At low node levels, pods per square meter seems to be limited by the number of nodes, but at higher node levels there was no relationship between nodes and pods.

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Soybean Reproductive Sink Size and Short‐term Reductions in Photosynthesis during Flowering and Pod Set

Cited by 44 publications

References 33 publications

Plant densities and modulation of symbiotic nitrogen fixation in soybean

Plant densities and modulation of symbiotic nitrogen fixation in soybean

Effects of elevated CO2 concentration and temperature on seed production and nitrogen concentration in soybean (Glycine max (L.) Merr.)

The Relationship between the Number of Nodes and Pods in Soybean Communities

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