Thomas J, Ross C W, Chastain C J, Koomanoff N, Hendrix J E
Department of Botany and Plant Pathology, Colorado State University, Fort Collins, Colorado 80523.
Plant Physiol. 1981 Jul;68(1):107-10. doi: 10.1104/pp.68.1.107.
The mechanism of cytokinin-induced cell expansion in cotyledons excised from dark-grown seedlings of radish (Raphanus sativus L.) and cucumber (Cucumus sativus L.) was studied. Cotyledons were incubated in dim light with or without 17 micromolar zeatin for periods up to 3 days. Fresh weights and osmotic potentials were measured daily. Cell wall extensibility properties were measured before and after the growth period. Also, experiments in which radish cotyledons were grown in mannitol solutions of various concentrations were performed. Comparisons of growth rates and increases of tissue osmotic potentials (toward zero) during growth without mannitol indicate that wall extensibility increased during the growth period and that this extensibility was enhanced by zeatin.Extensibility values derived from growth rates in mannitol provided indirect evidence of zeatin-increased wall extensibility. These conclusions were verified by direct measurements of plasticity with an Instron extensiometer. Thus, growth stimulation of excised cotyledons by cytokinins apparently involves wall loosening, in addition to previously demonstrated increases of K(+) absorption and formation of reducing sugars.
研究了细胞分裂素诱导萝卜（Raphanus sativus L.）和黄瓜（Cucumus sativus L.）黑暗中生长的幼苗子叶细胞扩张的机制。将子叶在弱光下培养，添加或不添加17微摩尔玉米素，培养3天。每天测量鲜重和渗透势。在生长前后测量细胞壁伸展性。此外，还进行了萝卜子叶在不同浓度甘露醇溶液中生长的实验。比较无甘露醇生长期间的生长速率和组织渗透势（趋于零）的增加表明，生长期间细胞壁伸展性增加，且玉米素增强了这种伸展性。从甘露醇中生长速率得出的伸展性值间接证明了玉米素增加了细胞壁伸展性。这些结论通过使用英斯特朗延伸仪直接测量可塑性得到了验证。因此，细胞分裂素对离体子叶的生长刺激显然除了先前证明的钾离子吸收增加和还原糖形成外，还涉及细胞壁松弛。
