Inducing a possible state of senescence in developing barley seedlings by applying the α‐chloroacetamide propachlor

Abstract

Summary:Propachlor (5, 50, 500 M) applied to the roots of barley (Hordeum vulgare L.) seedlings after 7 and 10 days, respectively, induces decreasing accumulation of fresh matter and dry matter; shoot length and root length are reduced. There was observed higher Hill activity, but lower O2‐evolution per unit dry weight and per seedling as calculated from Hill measurements. In the herbicide treated seedlings lower amounts of chlorophylls and carotenoids were found with decreasing ratios of chlorophylls/carotenoids and higher ratios of xanthophylls/β‐carotene. The ratios of chlorophyll a/benzoquinones decreased with regard to the control data. The accumulation of the single benzoquinones (on a chlorophyll basis), as related to the respective control values, is greater for α‐tocopherol, less for plastoquinone‐9 and even less for α‐tocoquinone. From the data obtained it is assumed that propachlor induces a state of senescence in the chloroplast. Propachlor seems to antagonize the known effects of exogenous indol‐3‐acetic acid. Questions of interaction of herbicide/phytohormone in this connection are discussed.