Plant Physiol.
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Plant Physiology 68:107-110 (1981)
© 1981 American Society of Plant Biologists

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Articles

Cytokinin-Induced Wall Extensibility in Excised Cotyledons of Radish and Cucumber 1

Jerry Thomas2, Cleon W. Ross3, Chris J. Chastain4, Nancy Koomanoff and John E. Hendrix

Elizabeth Van Volkenburgh

Department of Botany and Plant Pathology, Colorado State University, Fort Collins, Colorado 80523, Department of Botany, University of Washington, Seattle, Washington 98195

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.

2 Present address: Department of Botany and Microbiology, Arizona State University, Tempe, AZ 85281.

3 To whom reprint requests should be addressed.

4 Present address: Department of Botany, University of Illinois, Urbana, IL 61801.

1 This work was supported by National Science Foundation Grants PCM76-11915 and PCM78-04304.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1981 by the American Society of Plant Biologists