Bandurski R S, Schulze A
Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, USA.
Adv Space Res. 1983;3(9):229-35. doi: 10.1016/0273-1177(83)90061-3.
Numerous studies, particularly those of H. Dolk in the 1930's, established by means of bio-assay, that more growth hormone diffused from the lower, than from the upper side of a gravity-stimulated plant shoot. Now, using an isotope dilution assay, with 4,5,6,7 tetradeutero indole-3-acetic acid as internal standard, and selected ion monitoring-gas chromatography-mass spectrometry as the method of determination, we have confirmed Dolk's finding and established that the asymmetrically distributed hormone is, in fact, indole-3-acetic acid (IAA). This is the first physico-chemical demonstration that there is more free IAA on the lower sides of a geo-stimulated plant shoot. We have also shown that free IAA occurs primarily in the conductive vascular tissues of the shoot, whereas IAA esters predominate in the growing cortical cells. Now, using an especially sensitive gas chromatographic isotope dilution assay we have found that the hormone asymmetry also occurs in the non-vascular tissue. Currently, efforts are directed to developing isotope dilution assays, with picogram sensitivity, to determine how this asymmetry of IAA distribution is attained so as to better understand how the plant perceives the geo-stimulus.
众多研究，尤其是20世纪30年代H. 多尔克所做的那些研究，通过生物测定法证实，重力刺激下的植物茎干中，从下侧扩散出的生长激素比从上侧扩散出的更多。如今，我们使用同位素稀释分析法，以4,5,6,7-四氘代吲哚-3-乙酸作为内标，并采用选择离子监测气相色谱-质谱联用法作为测定方法，证实了多尔克的发现，并确定这种不对称分布的激素实际上就是吲哚-3-乙酸（IAA）。这是首次通过物理化学方法证明，在重力刺激下的植物茎干下侧存在更多的游离IAA。我们还表明，游离IAA主要存在于茎干的传导维管组织中，而IAA酯在生长的皮层细胞中占主导地位。现在，通过一种特别灵敏的气相色谱同位素稀释分析法，我们发现这种激素不对称现象也存在于非维管组织中。目前，研究工作致力于开发具有皮克灵敏度的同位素稀释分析法，以确定IAA分布的这种不对称是如何形成的，从而更好地理解植物是如何感知重力刺激的。
