Lagerstedt H B, Langston R G
Department of Plant Sciences, Texas A. & M. University, College Station, Texas.
Plant Physiol. 1967 May;42(5):611-22. doi: 10.1104/pp.42.5.611.
Kinetin has generally been thought to be immobile in plants. This was confirmed in the case of laminar applications in this study, but not in regard to petiole, vein, or root applications. Radioactivity from kinetin-8-(14)C (Kn()) moved freely in the vascular system of several types of leaves. This movement was usually distal to the point of application and seemed to occur with the transpiration stream. Basipetal as well as acropetal translocation of radioactive kinetin was achieved in tobacco leaves. The translocated material was extracted from veinal tissue, shown to be radioactive, and to be able to retard senescence. Similar but less decisive results were obtained from agar blocks inserted into the vascular system of leaves receiving Kn() by petiole uptake.A bioassay employing disks from primary bean leaves was developed for the qualitative determination of substances like kinetin which possess the ability to retard chlorophyll breakdown and plant senescence. The use of radioactive kinetin provided a refinement in this bioassay because treated non-senescent areas could be correlated with exposed areas on radioautographs made from dried leaf disks.Root treatments showed that cotton seedlings did not take up Kn(*) but that similarly treated tobacco seedlings both absorbed and translocated the isotope readily.
人们普遍认为激动素在植物体内是不移动的。本研究中对叶片进行分层施用的情况证实了这一点，但叶柄、叶脉或根部施用的情况并非如此。来自激动素 -8-(14)C（Kn()）的放射性物质在几种类型叶片的维管系统中自由移动。这种移动通常是向施用点的远端，并且似乎与蒸腾流一起发生。在烟草叶片中实现了放射性激动素的向基运输以及向顶运输。从叶脉组织中提取出的转运物质显示具有放射性，并且能够延缓衰老。通过叶柄吸收向接受Kn()的叶片维管系统中插入琼脂块也得到了类似但不太确定的结果。开发了一种使用菜豆初生叶圆盘的生物测定法，用于定性测定具有延缓叶绿素分解和植物衰老能力的物质，如激动素。放射性激动素的使用使这种生物测定法更加精确，因为处理过的未衰老区域可以与由干燥叶片圆盘制成的放射自显影片上的暴露区域相关联。根部处理表明，棉花幼苗不吸收Kn(*)，但同样处理的烟草幼苗既能吸收又能轻易转运该同位素。
