EFFECTS OF 3 PHENOLIC-ACIDS ON CHLOROPHYLL CONTENT AND GROWTH OF SOYBEAN AND GRAIN-SORGHUM SEEDLINGS

Experiments were designed to test the hypothesis that interference with chlorophyll [Chl] metabolism may be one mechanism of inhibition of plant growth in allelopathic interactions. Effects of ferulic, p-coumaric, and vanillic acids on soybean and grain sorghum growth and chlorophyll content were quantified and compared after seedlings were treated with these compounds in a nutrient culture. Following a 6 day treatment cycle, dry weights of soybean seedlings were reduced by both 10-3 M and 5 .times. 10-4 M treatments of ferulic, p-coumaric and vanillic acids. Soybean weight reductions in each case were paralleled by a significant reduction in the concentration (.mu.g Chl/mg dry wt) of Chl a and b and total Chl in the unifoliate leaves. Sorghum seedling growth was also reduced by each of the compounds at the 5 .times. 10-4 M level, but leaf Chl concentration was not below that of control plants.