Abstract
Flowering and pod set pattern were examined in racemose inflorescences of cowpea ( Vigna unguiculata). Anthesis occurs in acropetal succession where basal flowers set into pods while those at the distal end abscise either as flowers or immature pods. Increase in the time lag between anthesis on successive racemes reduced chances of pod set in flowers that are produced late. Application of triiodobenzoic acid (TIBA) to the pedicel of the dominant developing pod enhanced transport of 14C sucrose to the upper racemes indicating that auxin transport from the dominant sink suppresses metabolite transport to recessive sinks thereby inhibiting development. The signal auxin moving from early produced dominant sink accelerates abscission of later formed sinks. This was tested in experiments using well defined debladed cotton ( Gossypium hirsutum) petiole explants. In the various explants used, application of IAA to one of the petioles hastened abscission of untreated petioles. However, inhibition of IAA transport by TIBA overcame auxin induced abscission. Radiolabel studies using 14C IAA indicate that high concentration of diffusible IAA moving from a dominant sink inhibits basipetal movement of IAA from other competing sinks, thereby causing accelerated abscission. These observations support the hypothesis that diffusible IAA moving from a dominant sink acts as a correlative signal regulating abscission of other recessive sinks.
Published Version
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