EFFECT OF BENZOIC ACID AND ITS DERIVATIVES ON PLANT METABOLISM: 6- EFFECT OF CHLOROBENZOIC ACID DERIVATIVES ON THE CARBOHYDRATE METABOLISM OF STARVED AND SUCROSE-FED ETIOLATED BARLEY LEAVES
The effects of chlorobenzoic acids on respiration, sucrose absorption, and carbohydrate metabolism of etiolated barley leaves were studied. The results showed that respiration was retarded to the same extent irrespective of position of substitution, in the presence of these substances; inhibition was more pronounced at higher concentrations of chlorobenzoic acids. At low concentrations, o-chlorobenzoic acid enhanced sucrose uptake and p-chlorobenzoic inhibited uptake while at higher concentrations, both compounds inhibited sucrose uptake by etiolated barley leaves.Tissue analysis for carbohydrates showed a decrease in all carbohydrate fractions of treated leaves compared to the control samples. Even the sucrose-fed treated samples showed a carbohydrate content similar to that of the samples starving in distilled water in spite of the variable amounts of sugars absorbed by such samples.These observations, together with excretion of some copper-reducing substances that disappeared after clearing, support the previous suggestion (4) that the tissue carbohydrates were mostly transformed to non-sugar substances that might have been excreted as a result of increased permeability in the presence of the chlorobenzoic acids. This suggestion, together with the possibility of deactivation of the respiratory dehydrogenases, may explain the reduced rates of respiration of the treated samples.