Canopy position has a profound effect on soybean seed composition

Abstract

Although soybean seeds appear homogeneous, their composition (protein, oil and mineral concentrations) can vary significantly with the canopy position where they were produced. In studies with 10 cultivars grown over a 3-yr period, we found that seeds produced at the top of the canopy have higher concentrations of protein but less oil and lower concentrations of minerals such as Mg, Fe, and Cu compared to seeds produced at the bottom of the canopy. Among cultivars, mean protein concentration (average of different positions) correlated positively with mean concentrations of S, Zn and Fe, but not other minerals. Therefore, on a whole plant basis, the uptake and allocation of S, Zn and Fe to seeds correlated with the production and allocation of reduced N to seed protein; however, the reduced N and correlated minerals (S, Zn and Fe) showed different patterns of allocation among node positions. For example, while mean concentrations of protein and Fe correlated positively, the two parameters correlated negatively in terms of variation with canopy position. Altering the microenvironment within the soybean canopy by removing neighboring plants at flowering increased protein concentration in particular at lower node positions and thus altered the node-position gradient in protein (and oil) without altering the distribution of Mg, Fe and Cu, suggesting different underlying control mechanisms. Metabolomic analysis of developing seeds at different positions in the canopy suggests that availability of free asparagine may be a positive determinant of storage protein accumulation in seeds and may explain the increased protein accumulation in seeds produced at the top of the canopy. Our results establish node-position variation in seed constituents and provide a new experimental system to identify genes controlling key aspects of seed composition. In addition, our results provide an unexpected and simple approach to link agronomic practices to improve human nutrition and health in developing countries because food products produced from seeds at the bottom of the canopy contained higher Fe concentrations than products from the top of the canopy. Therefore, using seeds produced in the lower canopy for production of iron-rich soy foods for human consumption could be important when plants are the major source of protein and human diets can be chronically deficient in Fe and other minerals.

Kansas Field Research 2019

“…Differential seed yield and nutritional quality throughout the plant canopy might be related to nutrient remobilization, branching, and growth rate, as well as the pod-setting and seed-filling variability. According to Huber et al (2016), these differences in seed composition throughout the canopy can be studied to improve soybean quality by harvesting specific portions separately.…”

Comparison and Application of Non-Destructive NIR Evaluations of Seed Protein and Oil Content in Soybean Breeding

“…In soybean, NIR measurements of protein and oil have been extensively used in basic research [17,28,32,43]. These assessments have also been employed in the USDA Uniform Soybean Tests and Regional Quality Testes [44][45][46].…”

“…For instance, seed size and morphological characteristics may cause the spectral variance within seeds of a same cultivar [27]. In addition, the percentage of seed nutrient components within a plant may vary and is associated with seed position where the seed developed [28][29][30]. The difference in seed composition attributed to seed position within a plant is not inheritable.…”

Comparative Analysis of Perennial and Annual Phaseolus Seed Nutrient Concentrations

“…may preferentially partition ion contents to nearby seeds [52]. Position along a plant's stem has been shown to impact nutrient allocation in soybean seeds [23] and grapevine leaves [22]. Future work is needed to comprehensively sample Phaseolus seeds from throughout the plant in order to determine the effect of seed position on nutrient concentrations in this genus.…”

“…Environmental conditions (e.g., production site, soil conditions, temperature patterns) and agricultural practices (e.g., irrigation, fertilizer impacts) can also influence nutritive properties of beans [17][18][19]. Many other factors may also influence nutrient quality, including position of the seed pod along the plant stem, developmental stage, post-harvest processing, and quantity of anti-nutrients (compounds that interfere with nutrient absorption), such as trypsin inhibitors, hemagglutinin, tannin, and phytic acid [15,23]. Quantifying concentrations of essential nutrients and understanding their patterns of covariation in plant species used for food is critical for developing food systems that minimize nutrient deficiencies.…”