The validity of using a single soybean variety to evaluate the growth regulatory activity of chemicals

Abstract

Forty six soybean (Glycine max [L.] Merr.) varieties were evaluated for their vegetative response to a foliar application of abscisic acid, benzyladenine, or o-methoxyphenyl phosphinic acid (OMPA). Varietal responses to each chemical ranged from no effect to severe growth retardation. When the same varieties were evaluated for their response to water stress, the length of time required for severe wilting ranged from 48 h to 120 h. A cluster analysis was used to relate the coefficient of parentage of the varieties with their response to chemicals or water stress. The response of a variety to one of the chemicals did not predict the response to a different chemical. Further, the response of a variety to a chemical did not predict the response of a similar variety to the same chemical. The water stress rating was neither related to the chemical responses nor to the coefficient of parentage for the varieties in the test. The effects of night interruption and darkness were more pronounced on northern than on southern varieties, analogous with the pattern of reproductive regulation by photoperiod.