The effect of the suspensor and gibberellic acid on Phaseolus vulgaris embryo protein content

The role of the suspensor in the early development of the dicot embryo has not yet been defined. It has been described as merely an anchor and also as the major route of nutrients into the embryo. In order to further elucidate the role of the suspensor, early 0.2-mm and late heart stage 0.5-mm Phaseolus vulgaris (var. Taylor's Horticultural) embryos have been examined in tissue culture. It is known that Phaseolus embryos in culture at low osmotic potential will germinate precociously and that embryos in culture at high osmotic potential will either fail to grow or form callus. Optimum sucrose concentrations for continued, normal embryonic development of 0.2 mm and 0.5 mm P. vulgaris in tissue culture with Gamborg B5 medium were determined to be 12 and 6%, respectively. Protein content was examined in embryos and suspensors. Results showed that both 0.2- and 0.5-mm embryos required an attached suspensor for maximum protein content. Protein levels were substantially decreased when the embryo was cultured detached from or without the suspensor. Gibberellic acid at 10(-6) to 10(-7) M restored the protein content to that of freshly excised embryos.