Growth inhibition of lettuce (Lactuca sativa L.) roots by α-amino acids, 2-amino-3-cyclopropyl-butanoic acid and 2-amino-5-chloro-4-pentenoic acid, isolated from Amanita castanopsidis Hongo

Abstract

The effect of two α-amino acids, 2-amino-3-cyclopropyl-butanoicacid (ACPBA) and 2-amino-5-chloro-4-pentenoic acid (ACPA) on the growth oflettuce (Lactuca sativa L.) roots was investigated. BothACPBA and ACPA at 10−4 significantly inhibitedgrowth of roots of light-grown seedlings, while they had no effect on hypocotylgrowth. The lengths of cortical cells in the mature region of roots that hadbeen exposed to either compound were significantly shorter than those ofcontrolroots. Treatment with ACPBA and ACPA significantly decreased the mechanicalextensibility of root cell walls prior to the start of inhibition of rootgrowth. On the other hand, these compounds did not decrease the osmoticconcentration of the cell sap in root tissues. These results suggest that ACPBAand ACPA inhibit the cell elongation process of lettuce roots by decreasing themechanical extensibility of cell walls.