Effects of three phenolic acids on chlorophyll content and ions uptake in cowpea seedlings

This study was conducted to test the hypothesis that interfering with chlorophyll metabolism and ion uptake may be mechanisms through which some phenolic acids inhibit the growth of cowpea seedlings. Three concentrations (10(-4) M, 5 × 10(-4) M, and 10(-3) M) of each of syringic, caffeic, and protocatechuic acids were used to test their effects using sand-culture medium. It was found that seedling growth, chlorophyll a, total chlorophyll, chlorophyll a/b ratio, and the uptake of N, P, K, Fe, and Mo were significantly reduced by most of the test concentrations of the phenolic acids. However, chlorophyll b content and the Mg uptake were not significantly affected by all the phenolic acid concentrations. Calcium uptake was significantly inhibited by 5 × 10(-4) M and 10(-3) M of caffeic acid and 5 × 10(-4) M of protocatechuic acid. In most cases, the reduction in dry weight was parallel to the reduction in chlorophyll content and ion uptake, and the reduction in chlorophyll was also parallel to the reduction in ion uptake. The relationships among the inhibition of dry weights, chlorophyll content, and ion uptake are briefly discussed.