Department of Chemistry and Soil Chemistry, Faculty of Sciences, University of Navarra, P.O. Box 273, 31080 Pamplona (Navarra), Spain.
J Plant Physiol. 2010 May 15;167(8):633-42. doi: 10.1016/j.jplph.2009.11.018. Epub 2010 Feb 24.
Numerous studies have reported the ability of humic substances to increase shoot growth in different plant species cultivated under diverse growth conditions. However, the mechanism responsible for this effect of humic substances is poorly understood. It is possible that the shoot promoting effect of humic substances involves a primary effect on root H(+)-ATPase activity and nitrate root-shoot distribution that, in turn, causes changes in the root-shoot distribution of certain cytokinins, polyamines and abscisic acid, thus affecting shoot growth. We investigated this hypothesis in the present study. The results showed that the root application of a purified humic acid causes a significant increase in shoot growth that is associated with an enhancement in root H(+)-ATPase activity, an increase in nitrate shoot concentration, and a decrease in roots. These effects were associated with significant increases in the shoot concentration of several cytokinins and polyamines (principally putrescine), concomitant with decreases in roots. Likewise, these changes in the root-shoot distribution of diverse active cytokinins correlated well to significant changes in the root-shoot distribution of several mineral nutrients. These results, taken together, indicate that the beneficial effects of humic substances on shoot development in cucumber could be directly associated with nitrate-related effects on the shoot concentration of several active cytokinins and polyamines (principally putrescine).
许多研究报告指出，腐殖质能够促进不同生长条件下多种植物物种的茎生长。然而，腐殖质产生这种效果的机制还不甚清楚。腐殖质促进茎生长的作用可能涉及对根 H(+)-ATP 酶活性和硝酸盐根-茎分布的直接影响，而这反过来又会引起某些细胞分裂素、多胺和脱落酸在根-茎中的分布发生变化，从而影响茎的生长。本研究对这一假说进行了验证。结果表明，纯化腐殖酸施用于根部会显著促进茎的生长，这与根 H(+)-ATP 酶活性增强、硝酸盐向茎中的转移增加以及根减少有关。这些效应与几种细胞分裂素和多胺（主要是腐胺）在茎中的浓度显著增加有关，同时根中的浓度降低。同样，各种活性细胞分裂素和多胺（主要是腐胺）在根-茎中的分布变化与几种矿质养分在根-茎中的分布变化密切相关。这些结果表明，腐殖质对黄瓜茎发育的有益影响可能与硝酸盐对几种活性细胞分裂素和多胺（主要是腐胺）在茎中的浓度的影响直接相关。
