The rate of pistillate and staminate flower differentiation and development of mono- and multi-pistillate-type cucumbers

Abstract

SummaryThe rates of differentiation of pistillate and staminate flower primordia were examined in a mono-pistillate type [‘Excellent fushinari No.1’ (EF1)] and two multi-pistillate (‘NK AN8’ and ‘028’) cucumber cultivars (Cucumis sativus L.). In order to modify the sexual differentiation of flowers from pistillate to staminate at the same nodes, half of the seedlings of all three cultivars were sprayed with AgNO3. The rates of differentiation of leaf and flower primordia did not vary between the three cultivars, nor between the AgNO3-treatment and the control. Sexual identity was discernible when three-to-five flower primordia had differentiated at each node in all cultivars. The number of staminate flower primordia per node increased with time in all cultivars.The rate of differentiation of staminate flower primordia was higher in ‘028’ than in ‘EF1’ and ‘NK AN8’. In contrast, the number of pistillate flower primordia ceased to increase when sexual identity became distinguishable. Only the primary pistillate flower primordium developed in ‘EF1’, while primary and secondary (occasionally tertiary) flower primordia developed in ‘028’. Other pistillate flower primordia at the same node ceased to develop at the sepal formation stage and degenerated. These results suggest that a high rate of differentiation and/or a low rate of degeneration of flower primordia results in the formation of many staminate and pistillate flowers per node in multi-pistillate-type cucumbers.