Flavonoid and Isoflavonoid Distribution in Developing Soybean Seedling Tissues and in Seed and Root Exudates
The distribution of flavonoids, isoflavonoids, and their conjugates in developing soybean (Glycine max L.) seedling organs and in root and seed exudates has been examined. Conjugates of the isoflavones daidzein and genistein are major metabolites in all embryonic organs within the dry seed and in seedling roots, hypocotyl, and cotyledon tissues at all times after germination. Primary leaf tissues undergo a programmed shift from isoflavonoid to flavonoid metabolism 3 days after germination and become largely predominated by glycosides of the flavonols kampferol, quercetin, and isorhamnetin by 5 days. Cotyledons contain relatively constant and very high levels of conjugates of both daidzein and genistein. Hypocotyl tissues contain a third unidentified compound, P19.3, also present in multiple conjugated forms. Conjugates of daidzein, genistein, and P19.3 are at their highest levels in the hypocotyl hook and fall off progressively down the hypocotyl. These isoflavones also undergo a programmed and dramatic decrease between 2 and 4 days in the hypocotyl hook. All root sections are predominated by daidzein and its conjugates, particularly in the root tip, where they reach the highest levels in the seedling. Light has a pronounced effect on the distribution of the isoflavones; in the dark, isoflavone levels in the root tips are greatly reduced, while those in the cotyledons are higher. Finally, the conjugates of daidzein and genistein and several unidentified aromatic metabolites are selectively excreted into root and seed exudates. Analysis of seed exudates suggests that this is a continuous, but saturable event. [1]
Carbon and Nitrogen Limitations on Soybean Seedling Development
Carbon and nitrogen limitations on symbiotically grown soybean seedlings (Glycine max [L.] Merr.) were assessed by providing 0.0, 1.0, or 8.0 millimolar NH4NO3 and 320 or 1,000 microliters CO2/liter for 22 days after planting. Maximum development of the Rhizobium-soybean symbiosis, as determined by acetylene reduction, was measured in the presence of 1.0 millimolar NH4NO3 under both levels of CO2. Raising NH4NO3 from 0.0 to 8.0 millimolar under 320 microliters CO2/liter increased plant dry weight by 251% and Kjeldahl N content by 287% at 22 days after planting. Increasing NH4NO3 from 1.0 to 8.0 millimolar under 320 microliters CO2/liter increased total dry weight and Kjeldahl N by 100 and 168%, respectively, on day 22. Raising CO2 from 320 to 1,000 microliters CO2/liter during the same period had no significant effect on Kjeldahl N content of plants grown with 0.0 or 1.0 millimolar NH4NO3. The maximum CO2 treatment effects were observed in plants supplied with 8.0 millimolar NH4NO3, where dry weight and Kjeldahl N content were increased 64% and 20%, respectively. An increase in shoot CO2-exchange rate associated with the CO2-enrichment treatment was reflected in a significant increase in leaf dry weight and starch content for plants grown with 1,000 microliters CO2/liter under all combined N treatments. These data show directly that seedling growth in symbiotically grown soybeans was limited primarily by N availability. The failure of the CO2-enrichment treatment to increase total plant N significantly in Rhizobium-dependent plants indicates that root nodule development and functioning in such plants was not limited by photosynthate production. [2]
Arginine degradation by arginase in mitochondria of soybean seedling cotyledons
Arginase (EC 3.5.3.1) localization was studied in soybean (Glycine max L.) seedling cotyledons. Subcellular fractionation in a discontinuous Percoll gradient showed that arginase was localized in the mitochondrion. Arginine (Arg) uptake by mitochondria was demonstrated by co-sedimentation of [3H]Arg-derived label and the mitochondrial marker enzyme cytochrome c oxidase. Arginine uptake was complete in about 10 min. Since detergent but not NaCl released most label, we conclude that Arg was taken up and not bound to the organellar surface. Arginine transport was not saturable, at least up to 20 mM. Basic amino acids were the best inhibitors of Arg uptake. The uncoupler 2,4-dinitrophenol did not inhibit Arg uptake. At least 30% of L-[guanido-14C]Arg taken up by mitochondria was degraded by arginase in seedling cotyledons, while little or no degradation was detected in mitochondria from developing embryos, even though the Arg uptake level was similar in both mitochondrial preparations. These results are consistent with our previously reported pattern of arginase expression and urea accumulation during embryo development and seed germination (A. Goldraij and J.C. Polacco, 1999, Plant Physiol. 119: 297–303). The lack of Arg degradation allows developing embryos to conserve Arg, the main N-reserve amino acid utilized by germinating soybean. [3]
Micronutrients Distribution in Soybean Plant with Zn, Fe, and Mn Application
In order to investigate the effect of some of micronutrients application on micronutrient distribution, partitioning, and their ratio in different parts of soybean plant; we conducted an experiment in field conditions at Kermanshah, Iran, 2010 and 2011. Three levels of zinc (0, 20, 40 kg.ha-1 from ZnSo4 source); iron (0, 25, 50 kg.ha-1 from FeSo4 source) and manganese (0, 25, 40 kg.ha-1 from MnSo4 source) were applied. Based on results, it was found that Zn and Mn concentrations increased within the plant with micronutrient fertilizers application. The highest Zn concentration was observed in pod, but Maximum Fe and Mn concentrations recorded in leaves. With increases in soybean old and reach to full maturity stage, the Zn, Fe, and Mn content in tissue plant were decreased. The results indicated that with Zn application [Zn]/[Fe] and [Zn]/[Mn] ratios in seed increased. With Fe fertilizer application [Zn]/[Fe] ratio was decreased, but had no effect on [Zn]/[Mn] ratio. [4]
Effect of Plant Growth Regulators and Their Time of Application on Yield Attributes and Quality of Soybean
Plant growth regulators play important roles in plant growth and development, but little is known about the roles of plant growth regulators in yield components and seed qualities of soybean. In this study, salicylic acid, gibberellic acid (GA3), kinetin and distilled water (control) were sprayed to soybean (BARI Soybean-6) at the vegetative stage, flower initiation stage, pod initiation stage, flower + pod initiation stage in the pot experiment under field condition during November, 2013 to March, 2014. Treatments were arranged in a Randomized Complete Block Design (RCBD) with five replications. The different plant growth regulators and their time of application showed significant effect on number of pods plant-1, pod length, number of seeds pod-1, 100-seed weight, stover yield, biological yield, harvest index, seed grading (% by weight), protein and moisture content in seed of soybean. Salicylic acid gave the highest number of seeds pod-1, harvest index, small size seed, protein and moisture content in seed (1.60, 39.06%, 19.47%, 44.56% and 12.91%, respectively). Kinetin spray produced the maximum 100-seed weight (11.58 g). Application of growth regulators at vegetative stage produced the highest stover yield (6.46 g plant-1), flower initiation stage gave the larger size seed (59.09%), pod initiation stage showed the maximum pod length (2.43 cm), highest moisture content in seed (13.50%) and spray at flower + pod initiation stage produced the maximum 100-seed weight (12.00 g), harvest index (43.42%), medium size seed (32.53%), protein content in seed (44.31%). Among the treatment combinations the application of salicylic acid at flower and pod initiation stage showed the highest yield attributes and maximum protein content compared to those of other growth regulators.[5]
Reference
[1] Graham, T.L., 1991. Flavonoid and isoflavonoid distribution in developing soybean seedling tissues and in seed and root exudates. Plant physiology, 95(2), pp.594-603.
[2] Williams, L.E., Dejong, T.M. and Phillips, D.A., 1981. Carbon and nitrogen limitations on soybean seedling development. Plant Physiology, 68(5), pp.1206-1209.
[3] Goldraij, A. and Polacco, J.C., 2000. Arginine degradation by arginase in mitochondria of soybean seedling cotyledons. Planta, 210(4), pp.652-658.
[4] Kobraee, S., NoorMohamadi, G., HeidariSharifAbad, H., DarvishKajori, F. and Delkhosh, B., 2013. Micronutrients distribution in soybean plant with Zn, Fe, and Mn application. Annual Research & Review in Biology, pp.83-91.
[5] Khatun, S., Roy, T.S., Haque, M.N. and Alamgir, B., 2016. Effect of plant growth regulators and their time of application on yield attributes and quality of soybean. International Journal of Plant & Soil Science, pp.1-9.