Interactive effects of H 2S and O 3 on the yield of snap beans ( Phaseolus vulgaris L.)

Abstract

Snap beans ( Phaseolus vulgaris L., cv. GV 50) were grown in a field using standard method, and 7.5 m plots were fumigated with concentrations of ozone ranging from 0.046 to 0.127 ppm and hydrogen sulfide from 0.30 to 7.0 ppm in several combinations. Gas mixtures were introduced into the plant canopy by means of a blower and plastic duct assembly with 60 cm walls around each plot, thus eliminating any serious chamber problems. Fumigations for 4 hr/day began after emergence of the first trifoliate leaf and continued throughout the growing period until pod set (day 40). Leaf injury scores and number of leaves were recorded weekly throughout the experimental period. Pod yield, total plant weight, leaf area, branch, raceme, and pod number were measured on ten plants/plot at market maturity 55 days after emergence; bulk harvests were taken at 62 days. A significant dose-response relationship for H 2S was found for leaf visible injury during the vegetative growth period, but no interaction with O 3 was observed. Three regression analyses were used to analyze the data: individual plant responses grouped according to fumigation treatment were regressed on dose, individual regressions for each plot were run, and plot response means were regressed on plot dose means. System response was described most accurately by the first method. Plants harvested at 55 days showed a 58% reduction in total pod fresh weight [from 42.4 g to 20.0 g (983-464 g/m 2)] due to the highest H 2S + O 3 dose compared tothe unfumigated plants. Plants harvested at 62 days had recovered from the air pollution stress and showed only a 1% reduction in pod fresh weight/plant.