biologia plantarum

Biologia plantarum 33:81, 1991 | DOI: 10.1007/BF02897783

Influence of ACC and Ethephon on cell growth in etiolated lupin hypocotyls. dependence on cell growth state

A. Ortuño¹, J. A. Del Rio¹, J. L. Casas¹, M. Serrano¹, M. Acosta¹, J. Sanchez-Bravo¹

¹ Departamento de Biologia Vegetal, Universidad de Murcia, Espinardo, Spain

The possible implication of ethylene on the growth regulation of etiolated lupin hypocotyls was investigated. Excised hypocotyl sections from actively growing seedlings produced ethylene at a rate of 3 nmol h^-1 g^-1 min^-1. The rate of ethylene production was increased about 7 times when sections were treated with 10 mM 1-aminocyclopropane-1-carboxylic acid (ACC). Measurement of endogenous ACC showed that 95 % of total ACC (64.2 nmol g^-1 min^-1) corresponded to conjugated ACC.
Treatments to intact seedlings with the ethylene precursor ACC, and the ethylene generating compound, 2-chloroethyl phosphonic acid (ethephon) during the cell elongation phase of the hypocotyl (from 7 to 21 dage), modified the cell growth of the organ. ACC (1 or 5 mM) or low concentrations of ethephon (0.66 mM) produced a transient decrease in the growth rate without modifying the final length of the hypocotyls. Higher concentrations of ethephon reduced the final length; the younger the seedlings were, the greater the reduction. Simultaneously to inhibition of cell elongation, ethephon produced stimulation of the radial expansion of cells in pith and cortex.
The growth inhibition period, which lasted for 2 days after the treatments, was followed by another period in which the growth rate of treated plants surpassed that of the control. In both cases differences were observed along the hypocotyls due to the different growth status of the cells. It is suggested that the sensitivity to ethylene and the metabolism of ethylene depend on the growth status of the cells.

Received: October 23, 1989; Accepted: June 1, 1990; Published: March 1, 1991  Show citation