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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 effects of nitrogen (N) forms (ammonium- or nitrate-N) on plant growth under salinity stress [150 mmol sodium chloride (NaCl)] were studied in hydroponically cultured cotton. Net fluxes of sodium (Na+), ammonium (NH4+), and nitrate (NO3−) were also determined using the Non-Invasive Micro-Test Technology. Plant growth was impaired under salinity stress, but nitrate-fed plants were less sensitive to salinity than ammonium-fed plants due mainly to superior root growth by the nitrate-fed plants. The root length, root surface area, root volume, and root viability of seedlings treated with NO3-N were greater than those treated with NH4-N with or without salinity stress. Under salinity stress, the Na+content of seedlings treated with NO3-N was lower than that in seedlings treated with NH4-N owing to higher root Na+efflux. A lower net NO3−efflux was observed in roots of nitrate-fed plants relative to the net NH4+efflux from roots of ammonium-fed plants. This resulted in much more nitrogen accumulation in different tissues, especially in leaves, thereby enhancing photosynthesis in nitrate-fed plants under salinity stress. Nitrate-N is superior to ammonium-N based on nitrogen uptake and cotton growth under salinity stress. [ABSTRACT FROM PUBLISHER]

Genotypic differences in potassium (K) uptake and utilization were compared for eight cotton cultivars in growth chamber and field experiments. Four of the cultivars ('SGK3', 'SCRC18', 'SCRC21' and 'SCRC22') typically produce lower dry mass and the other four ('Nannong8', 'Xiangza2', 'Xinluzao12' and 'Xiangza3') produce greater dry mass in K-deficient solution (0.02 mM). The mean dry weight of seedlings (five-leaf stage) of cultivars with greater biomass was 155% higher than that of cultivars with lower biomass yield under K deficiency. However, all the genotypes had similar dry matter yields in K-sufficient solution (2.5 mM). Thus, the four cultivars with superior biomass yield under low K medium may be described as K efficient cultivars while the inferior cultivars may be described as K inefficient. Although seeds of the studied cultivars originated from different research institutes or seed companies, there were little differences in seed K content among them, irrespective of their K efficiency. Consequently, there were no significant differences in K accumulation in seedlings (4 d after germination in a K-free sand medium) just before transferring to nutrient solutions. However, the K efficient genotypes, on average, accumulated twice as much K at 21 d after transferring to K-deficient solution (0.02 mM). A much larger root system as well as a slightly higher uptake rate (K uptake per unit of root dry weight) may have contributed to the higher net K uptake by the K efficient cultivars. In addition, the K efficiency ratio (dry mass produced per unit of K accumulated) and K utilization efficiency (dry mass produced per unit of K concentration) of the K efficient cultivars exceeded those of the K inefficient genotypes by 29% and 234%, respectively, under K deficiency. On average, the K efficient cultivars produced 59% more potential economic yield (dry weight of all reproductive organs) under field conditions even with available soil K at obviously deficient level (60 mg kg-1). We noted especially that the four K inefficient cultivars studied were all transgenic insect-resistant cotton, suggesting that the introduction of foreign genes (Bt and CpTI) may affect the K use efficiency of cotton. [ABSTRACT FROM AUTHOR]