Effect of gibberellic acid on the formation and development of antheridia and oogonia in Chara vulgaris L.

Abstract

The experiments were performed on <em>Chara vulgaris</em> thalli cultivated in axenic conditions. It has been found that application of GA₃ at concentrations of 10^-9 -10^-4 M has no effect on the numbers of developing antheridia and oogonia. GA₃ stimulates the gemmation of capitular cells thus increasing the number of filaments in antheridia (by 45% when 10^-8 M is used). The number of mitotic cycles preceding the differentiation of spermatozoids is not significantly modified by this gibberellin. The number of spermatozoids in antheridia increases by about 20% when 10^-8 -10^-6 M GA₃ concentrations are used. GA₃ shortens the duration of spermatogenesis (by 2.5 days, at 10^-7 M concentration). This effect is due to a shortening of the mitotic cycles in filaments. On the other hand, the time of spermatozoid differentiation, which in the control material lasts about 5.3 days, is not changed significantly by GA₃. GA₃ hastens the maturation of oogonia and the formation of oospores - both effects are proportional to the GA₃ concentration used.