Effects of Date and Growth Regulators on the Culture of' Immature Zygotic Embryos of North American Ginseng

Abstract

As the zygotic embryo of North American ginseng (Panax quinquefolius L.) matured during stratification over 203 days it grew from 0.75 to 5.2 mm. Embryo excision and culturing on media containing different concentrations of two growth regulators, gibberellic acid (<TEX>$GA_3$</TEX>, 1 to 10 <TEX>${\mu}M$</TEX>) and benzyladenine (BA, 1 to 5 <TEX>${\mu}M$</TEX>), during stratification, showed that shoot and root number and the shoot, root and cotyledon length increased with increased stratification time. Gibberellic acid was the more effective growth regulator for increasing shoot and root number and shoot, root and cotyledon lengths. Immature embryos (stratified for up to 63 days) needed growth regulators for further development. Cultures on <TEX>$GA_3$</TEX> at the last culture date (stratified for 203 days) when embryos were mature, produced multiple shoots but there was no effect of <TEX>$GA_3$</TEX> concentration. Benzyladenine inhibited shoot and root growth regardless of embryo stratification. Growth regulators had little effect on cotyledon length of mature embryos. Embryos cultured on <TEX>$GA_3$</TEX> combined with BA were green on all culture dates whereas greening in the control and BA treatments increased with culture date. The BA treatments induced 100% swelling of the embryos on the final culture date while in the control and <TEX>$GA_3$</TEX> treatments there was no swelling. There was little or no curling in the control and BA treatments and a linear decrease in curling with culture date in the <TEX>$GA_3$</TEX> and <TEX>$GA_3$</TEX> + BA treatments.