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Roots absorb water and nutrients from the soil, give mechanical support to plants, and supply hormones that affect many physiological and biochemical processes. Roots also exert control over whole-plant growth and development by synthesizing plant hormones and controlling the uptake of mineral nutrients. Coronatine (COR) is an analogue of jasmonic acid and is a chlorosis-inducing non-hostspecific phytotoxin with an alleviative effect on plant growth under stress conditions. A 2-year field study was conducted to determine the effect of COR on the physiological and biochemical attributes of the root and the seed yield of soybean (Glycine maxL. Cv. Zhonghuang 13). COR was foliar-applied at 10 nM during the 7-trifoliolate leafs stage. Root dry weight was significantly increased on average by 37% with COR over the 2 years. The root nitrogen concentration increased by 19.2%, phosphorus concentration by 23.3%, and potassium concentration by 31.2% following COR application. The content of cytokinins was increased by 31.5% and 46.0%, while that of abscisic acid was decreased by 45.0% and 25.5% with COR over the 2 years. Seed yield was increased 7.0% in 2008 and 9.6% in 2009, respectively, due to COR application. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate the effect of silicon (Si) on soybean seedlings under (combined) drought and ultraviolet-B (UV-B) radiation stresses. Specifically, we determined dry matter accumulation and partitioning of the mineral elements in different organs of soybean seedlings using the inductively coupled plasma mass spectrometry (ICP-MS). The amount of dry matter accumulated in root, stem, and leaf of seedlings treated with (combined) drought and UV-B radiation stresses were lower than that of the control. Also, the content of macroelements in seedlings under the combined stress was lower than in those under control conditions. Changes in the contents of microelements varied according to the intensity of drought, UV-B radiation, and the organs of soybean. The relationship between the contents of mineral elements and the accumulation of dry matter also varied similarly. These results demonstrated that drought and UV-B radiation induced an alteration in the distribution of mineral elements in root, stem and leaf, leading to decreases in dry matter accumulation and inhibition of soybean growth. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate the potential of silicon (Si) for alleviating Ultraviolet-B (UV-B) radiation stress based on changes in biomass, physiological attributes and photosynthetic characteristics of two soybean (Glycine maxL.) cultivars, Kenjiandou 43 (‘K 43’) and Zhonghuang 35 (‘ZH 35’). The cultivars were raised with and without Si in the greenhouse, and then subjected to ambient, ambient + 2.7 kJ m−2d−1and ambient + 5.4 kJ m−2d−1of UV-B radiation. Depending on cultivar, plants suffered severe growth limitations under UV-B radiation, but the application of Si alleviated the adverse effects on growth and development by increasing the stem length, net photosynthetic rate (PN) and leaf chlorophyll content. Concurrently, it decreased the stomatal conductance (Sc) and intercellular carbon dioxide (CO2) concentration (Ci). In response to the UV-B radiation stress, the antioxidant enzyme activities of superoxide dismutase (SOD) increased by 41.2–72.7%, peroxidases (POD) by 49.5–85.7%, malodialdehyde (MDA) by 6.7–20.4% and soluble protein by 4.2–7.6%. The overall results indicated that media treatment with Si might improve soybean growth under elevated UV-B radiation through positive changes in biomass and some physiological attributes that were dependent on cultivar. [ABSTRACT FROM PUBLISHER]

LOS 5/ ABA 3 gene encoding molybdenum cofactor sulphurase is involved in aldehyde oxidase ( AO) activity in Arabidopsis, which indirectly regulates ABA biosynthesis and increased stress tolerance. Here, we used a constitutive super promoter to drive LOS 5/ ABA 3 overexpression in soybean ( Glycine max L.) to enhance drought tolerance in growth chamber and field conditions. Expression of LOS 5/ ABA 3 was up-regulated by drought stress, which led to increasing AO activity and then a notable increase in ABA accumulation. Transgenic soybean under drought stress had reduced water loss by decreased stomatal aperture size and transpiration rate, which alleviated leaf wilting and maintained higher relative water content. Exposed to drought stress, transgenic soybean exhibited reduced cell membrane damage by reducing electrolyte leakage and production of malondialdehyde and promoting proline accumulation and antioxidant enzyme activities. Also, overexpression of LOS 5/ ABA 3 enhanced expression of stress-up-regulated genes. Furthermore, the seed yield of transgenic plants is at least 21% higher than that of wide-type plants under drought stress conditions in the field. These data suggest that overexpression of LOS 5/ ABA 3 could improve drought tolerance in transgenic soybean via enhanced ABA accumulation, which could activate expression of stress-up-regulated genes and cause a series of physiological and biochemical resistant responses. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine if treatment with silicon (Si) may improve nutrient uptake by soybean under ultraviolet-B (UV-B) radiation stress. Soybean (Glycine max L.) cultivars, 'Kennong 18' (K 18) and 'Zhonghuang 13' (ZH 13), were grown in hydroponic cultures under ambient and supplemental levels of ultraviolet-B (UV-B, 280-315 nm) with and without Si. Supplemental UV-B radiation simulating 30% stratospheric ozone depletion significantly decreased plant biomass by 74.9 to 135.6%, increased leaf nitrogen (N) and phosphorus (P) by 9% and 16%, respectively, decreased leaf magnesium (Mg) contents by 9%, and calcium (Ca) by 24%. UV-B radiation caused a substantial increase in the allocation of P, potassium (K) and Ca to roots compared with stem and leaves, presumably to ensure sustained nutrient uptake under the stress. Silicon application improved the uptake of P and Mg by 11%, which favored the partitioning of dry mass to shoots under UV-B radiation and the allocation of tissue P and Ca to roots. The overall changes due to Si supported a reasonable increase in dry mass of the 'K 18' cultivar. [ABSTRACT FROM AUTHOR]

Abstract: Silicon (Si) may be involved in metabolic, physiological, and/or structural activity in higher plants exposed to abiotic and biotic stresses. This has not yet been determined due to the absence of direct evidence that it is part of the molecule of an essential plant constituent or metabolite. The aim of this study was to investigate the effect of silicon on soybean seedlings under drought and ultraviolet-B (UV-B) radiation stresses. The relative leaf water content (RWC), which was the main factor resulting in reduced growth in response to drought, increased 19.0% and 30.0% with Si application under drought and drought+UV-B stresses, respectively. Under UV-B radiation, the anthocyanin and phenol levels decreased 91.5% and 10.0% in the treatment of Si. Ultraviolet-B radiation and drought stress caused great membrane damage, as assessed by lipid peroxidation and osmolyte leakage, but Si application significantly reduced the membrane damage. Catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and hydrogen peroxide were observed under stress conditions. Proline increased primarily in drought-stressed seedlings and may be the drought-induced factor with a protective role in response to UV-B and silicon. Photosynthesis (P N) increased following Si application by 21.0%, 18.3% and 21.5% under UV-B radiation, drought and the combination, respectively. The physiological and biochemical parameters measured indicated that the UV-B light had more adverse effects on growth of soybean seedlings than drought, but the data also showed that Si could alleviate seedling damage under these stress conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Coronatine enhanced photosynthesis and 14C translocation under drought stress. [•] Coronatine-treated plants had better membrane stability and water status under drought stress. [•] Coronatine-treated plants exhibited higher antioxidant enzyme activities during drought stress. [•] Coronatine alleviated biomass reduction under drought stress. [Copyright &y& Elsevier]