Kinraide T B, Parker D R
Appalachian Soil and Water Conservation Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Beckley, West Virginia 25802-0867.
Plant Physiol. 1987 Mar;83(3):546-51. doi: 10.1104/pp.83.3.546.
Aluminum is a major constituent of most soils and limits crop productivity in many regions. Amelioration is of theoretical as well as practical interest because understanding amelioration may contribute to an understanding of the mechanisms of toxicity. In the experiments reported here 2-day-old wheat (Triticum aestivum L. cv Tyler) seedlings with 15-millimeter roots were transferred to solutions containing 0.4 millimolar CaCl(2) at pH 4.3 variously supplemented with AlCl(3) and additional amounts of a chloride salt. Root lengths, measured after 2 days in the test solutions, were a function of both Al activity and the cation activity of the added salt. Percent inhibition = 100 {Al(3+)}/({Al(3+)} + K(m) + alpha{C}(beta)) where {Al(3+)} is the activity of Al(3+) expressed in micromolar, {C} is the activity of the added cation expressed in millimolar, and K(m) (= 1.2 micromolar) is the {Al(3+)} required for 50% inhibition in the absence of added salt. For Ca(2+), Mg(2+), and Na(+) the values of alpha were 2.4, 1.6, and 0.011, respectively, and the values for beta were 1.5, 1.5, and 1.8, respectively. With regard to relative ameliorative effectiveness, Ca(2+) > Mg(2+) approximately Sr(2+) >> K(+) approximately Na(+). Other cations were tested, but La(3+), Sc(3+), Li(+), Rb(+), and Cs(+) were toxic at potentially ameliorative levels. The salt amelioration is not solely attributable to reductions in {Al(3+)} caused by increases in ionic strength. Competition between the cation and Al for external binding sites may account for most of the amelioration.
铝是大多数土壤的主要成分，在许多地区限制了作物生产力。改良不仅具有理论意义，也具有实际意义，因为了解改良有助于理解毒性机制。在本文报道的实验中，将根长15毫米的2日龄小麦（普通小麦品种泰勒）幼苗转移到含有0.4毫摩尔氯化钙（pH 4.3）的溶液中，该溶液分别添加了不同量的氯化铝和额外的氯化物盐。在测试溶液中培养2天后测量的根长，是铝活性和添加盐的阳离子活性的函数。抑制百分比=100×{Al(3+)}/({Al(3+)} + K(m) + α{C}(β))，其中{Al(3+)}是以微摩尔表示的Al(3+)活性，{C}是以毫摩尔表示的添加阳离子活性，K(m)（=1.2微摩尔）是在不添加盐的情况下50%抑制所需的{Al(3+)}。对于Ca(2+)、Mg(2+)和Na(+)，α值分别为2.4、1.6和0.011，β值分别为1.5、1.5和1.8。关于相对改良效果，Ca(2+)＞Mg(2+)≈Sr(2+)＞＞K(+)≈Na(+)。还测试了其他阳离子，但La(3+)、Sc(3+)、Li(+)、Rb(+)和Cs(+)在可能具有改良作用的水平下具有毒性。盐的改良作用并非完全归因于离子强度增加导致的{Al(3+)}降低。阳离子与铝争夺外部结合位点可能是大部分改良作用的原因。
