Anatomical changes in flower buds of lettuce (Lactuca sativa L.) treated with a GA3-solution for induction of male sterility

GA3 spraying of lettuce induces male sterility. Cafferent types of male sterile flowers developed; flowers with anthers containing some pol en grains which were not liberated (MSI) and flowers with only rudimentary anthers or with no anthers at all (MS2). From anatomical studies it appeared that great differences occurred for the effect of GA3 between flower buds, within buds between florets and within florets. Besides the developmental phase also the type of tissue has a certain influence. The lock-up of pollen grains by remnants of tapetum possibly hampered nutrition and prevented liberation of pollen accounting for the occurrence of MSI flowers. Buds without sporogenous tissue or with tumors instead might develop into MS2 flowers.