EFFECTS OF GROWTH REGULATING CHEMICALS ON THE OPENING OF VEGETATIVE AND FLORAL BUDS OF PEACH AND PEAR

Application of certain growth regulatinig substanices to the stein and leaves of plants often affects the rate of growth of the terminal and lateral buds. This effect has attracted the attention of many investigators, but up to now vegetative, rather than flower buds, have been studied (2, 3, 8). In general, the application of some of the growth regulating chemicals in relatively high concentrations, to the stems of succulent plants retards the growth of the vegetative buds. In some experiments these have been mixed with lanolini to form a paste, and then applied to the cut surface of decapitated stems with the result that the growth of buds below the treatment was inhibited (6). In other experiments, these substances inhibited bud growth when applied either directly to the buds or to the outer surface of the stem near the buds (5, 6). In a few experimenits the application of certain of these substances stimulated the growth and development of vegetative buds (1, 9). It has been reported that iaphthalenieacetic acid retarded the opening of the floral buds of the peach (10). If this were true under widely different conditions in the orchard (especially near the season of blooming) that fact would be of practical interest in coiniectioni with the prevenition of frost injury, since unopened buds are less sensitive to injury by cold than is the expanded flower. In some instances the delay of a week in blooming might mealn that severe frost injury could be avoided. In these experiments (10) WINKLEPLECK dissolved the acid in water at the rate of 125 mg. per liter, and the solutioin was then sprayed on the trees in the orchard prior to blossomiing. The treated trees reached full bloom eleven days later than did comparable unsprayed trees. This result indicated that the growth of the buds was retarded during the last stages of swelling and the opening of the petals was appreciably delayed. The petals of flowers on the treated trees were smaller than those on coiitrol trees, and the rate of maturation of fruit was delayed, but the final size of the fruit was not affected by treatment. In the experiments here reported results at varianee with the above mentioned were obtained. The methods employed consisted in usilngY different amoulnts of growth regulating substanees applied as sprays to branches of peach and pear trees both in the greenhouse and uncder orchard coniditions. 16