The role of leaves in sex expression in hemp and spinach.

When shoots of young plants of hemp (Cannabis sativa L.) and spinach (Spinacea oleracea L.) were cultured as cuttings and allowed to regenerate advenitious roots, ca. 80-85% became female (formed pistillate flowers) regardless of whether the leaves were left on the plants or were cut off (except for the 2-3 uppermost ones) after the beginning of adventitious-root formation. But when the leaves were cut off and the cuttings treated with gibberellic acid (GA3, 25 mg/l) ca. 77-80% of the plants became male (formed staminate flowers). The result was quite similar when roots and leaves of young hemp plants were removed at the same time and the cuttings treated with GA3. It is suggested that the leaves play an essential role in sex expression in hemp and spinach and that this role is related to gibberellin synthesis in the leaves.