INHIBITING INFLUENCE OF THE LEAVES ON THE PHOTOPERIODIC RESPONSE OF NOBLE SPINACH

Abstract

Various portions of intact and partially defoliated long day Nobel spinach plants were given long and short photoperiod treatments, to determine the influence of the leaves and bud on the flower forming stimulus. The bud was relatively insensitive to photoperiod, confirming results of previous workers. When only 1 leaf of intact plants was exposed to a long photoperiod (the remainder given a short photoperiod), floral primordia failed to form; when 3 leaves were exposed, floral primordia formed but no macroscopic buds or flower stalks developed during the exptl. period. If plants were defoliated to 1 and 3 leaves and given a long photoperiod treatment, they flowered almost as quickly as did intact plants so treated. The rate of flower stalk development was greater, however, the larger the number of leaves left on the plants. Evidently, leaves kept in an unfavorable short photoperiod exert an inhibiting influence on flower bud initiation and development in Nobel spinach.