Parrondo R T, Smith R C
Department of Botany, University of Florida, Gainesville, Florida 32611.
Plant Physiol. 1976 Apr;57(4):607-11. doi: 10.1104/pp.57.4.607.
Samples of primary root tissue of corn (Zea mays L.) were aged either in CaSO(4) solution or in humid air, after which they were immersed for 10 minutes in a solution containing 0.1 mm(86)RbCl. Aging in solution, but not in humid air, enhanced the subsequent rate of Rb(+) absorption. Excision of roots before aging was followed by greater enhancement than when exicision followed aging. The time course of aging of 1-cm segments from different portions of the root showed decreasing response with increasing distance from the root cap. The aging response of apical segments (5-15 mm from the root cap) could be detected within 10 minutes and usually reached a maximum within 2 hours. Rb(+) absorption by apical segments (5-15 mm) aged without the tip (0-5 mm) was more than double that by apical segments whose tips were left attached until the end of the aging period. When apical segments without the tip were aged for 2 hours in the CaSO(4) solution in which seedlings had previously been grown for 24 hours, the rate of absorption was only 63% of samples aged in fresh solution. When apical segments were aged for 2 hours in fresh solution containing excised tips floating free in the solution, the rate of Rb(+) absorption was 20% less than in samples aged in solution containing no excised tips. The data presented in this study are interpreted to indicate that a water-soluble metabolite, originating in the root tip and translocated basipetally, inhibits Rb accumulation.
玉米（Zea mays L.）初生根组织样本分别在硫酸钙溶液或潮湿空气中进行老化处理，之后将它们浸入含有0.1 mM（86）RbCl的溶液中10分钟。在溶液中老化而非在潮湿空气中老化，会提高随后的Rb（+）吸收速率。老化前切除根部比老化后切除根部的促进作用更强。来自根不同部位的1厘米切段的老化时间进程显示，随着与根冠距离的增加，反应逐渐减弱。根尖切段（距根冠5 - 15毫米）的老化反应在10分钟内即可检测到，通常在2小时内达到最大值。无根尖（0 - 5毫米）老化的根尖切段（5 - 15毫米）对Rb（+）的吸收是老化期结束时仍保留根尖的根尖切段的两倍多。当无根尖的根尖切段在幼苗先前生长24小时的硫酸钙溶液中老化2小时时，吸收速率仅为在新鲜溶液中老化样本的63%。当根尖切段在含有游离于溶液中的切除根尖的新鲜溶液中老化2小时时，Rb（+）的吸收速率比在不含切除根尖的溶液中老化的样本低20%。本研究中呈现的数据被解释为表明一种源自根尖并向基部运输的水溶性代谢物会抑制Rb的积累。
