【摘要】 镉 (Cd)污染和增强紫外线_B(UV_B)辐射对大豆 (Glycinemax)根系分泌物变化的研究表明 ,Cd污染促进了大豆根系有机化合物 (如有机酸、氨基酸、多肽和酰胺等 )的分泌 ,但该分泌作用受增强UV_B辐射的抑制。根系有机硫分泌只受较强胁迫条件促进 ,较高浓度Cd和较强的UV_B辐射对大豆根系有机硫分泌有协同促进作用。氮素含量主要受Cd胁迫影响 ,其变化可能有两方面原因 :1 )Cd胁迫下根系对有机含氮化合物 ,主要是多肽、氨基酸和酰胺的分泌增加 ;2 )Cd胁迫减少了根系对氮素的吸收 ,引起根际环境中残留氮素的升高。增强UV_B辐射对根际环境中氮素有一定影响 ,但不显著。研究结果表明了增强UV_B辐射在一定程度上影响Cd胁迫下大豆根系有机化合物的分泌作用 ,而且可能与大豆根系对重金属毒害的抗性有关更多还原

【Abstract】 An increase in ultraviolet_B （UV_B, 280₃15 nm） radiation reaching the earth’s surface due to depletion of the stratospheric ozone layer and heavy metal pollution due to industrial waste have become serious concerns. In order to understand the influence of enhanced UV_B radiation and heavy metal pollution on plant root growth, physiological metabolism, and tolerance to heavy metals, the effect of cadmium （Cd） associated with enhanced UV_B radiation on the excretion activity of soybean root was investigated. The full amounts of nitrogen, organic carbon, and sulfur excreted by soybean （ Glycine max ） root exposed to Cd 2+ pollution, enhanced UV_B radiation and both in combination were measured using the Kjeldahl method and a CS₃44 carbon and sulfur system （LECO USA）. The results showed that Cd 2+ could enhance root excretion of organic carbon, but the excretion was inhibited by enhanced UV_B radiation. Excretion of organic sulfur compounds was only accelerated by severe stress, that is a combination of higher Cd 2+ concentration and stronger UV_B radiation had a synergistic effect on excretion. Nitrogen content was mainly affected by Cd 2+ . The possible reasons were: 1) Cd 2+ pollution promoted roots to excrete more organic nitrogen compounds, such as amino acids and polypeptides; 2) Cd 2+ decreased absorption ability of roots, and nitrogen uptake from rhizosphere was reduced, thereby resulting in an increase in nitrogen content in the environment of the root. Nitrogen content in the environment could also be affected by enhanced UV_B radiation, but this effect was insignificant. The results indicated that UV_B radiation could alter the composition and proportion of root excretions, and, perhaps, affect plant tolerance to Cd 2+ stress.更多还原