The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138.
Plant Physiol. 1972 Feb;49(2):155-60. doi: 10.1104/pp.49.2.155.
The natural occurrence of cytokinins existing both in a free form and as a constituent of transfer RNA was examined in serial segments of young seedling roots of pea. Purified ethanol extracts of root apices were resolved into four factors capable of inducing soybean callus tissue proliferation. The most active factor was identified as zeatin or some closely related compound; it produced polyploid divisions and tracheary element differentiation when tested on cultured pea root segments. The terminal 0- to 1-millimeter root tip contained 43 to 44 times more free cytokinin on a fresh weight or a per cell basis than the next 1- to 5-millimeter root segment. Extracts of more proximal segments behind the tip contained no measurable free cytokinin. Acid hydrolysates of transfer RNA exhibited reproducible cytokinin activity. Bioassays revealed that the predominant amounts of free cytokinin and that present in transfer RNA were restricted to the extreme root tip. There was approximately 27 times more free cytokinin than the amount detected in transfer RNA in root apices.
我们在豌豆幼苗根的连续节段中检查了游离形式和作为转移 RNA 成分存在的细胞分裂素的自然发生情况。从根尖的提纯乙醇提取物中解析出四种能够诱导大豆愈伤组织增殖的因子。最活跃的因子被鉴定为玉米素或一些密切相关的化合物；当在培养的豌豆根段上测试时，它会产生多倍体分裂和导管元素分化。在新鲜重量或每细胞基础上，末端 0-1 毫米的根尖比下一个 1-5 毫米的根段含有多 43-44 倍的游离细胞分裂素。尖端后面更靠近的节段的提取物不含可测量的游离细胞分裂素。转移 RNA 的酸水解产物表现出可重复的细胞分裂素活性。生物测定表明，游离细胞分裂素和转移 RNA 中存在的主要物质都局限于极端根尖。在根尖中检测到的游离细胞分裂素比转移 RNA 中的含量多约 27 倍。
