POLLEN-TUBE DISTRIBUTION IN THE KIWIFRUIT (ACTINIDIA-DELICIOSA A. CHEV. LIANG,C.F.) PISTIL IN RELATION TO ITS REPRODUCTIVE PROCESS

High resolution light and fluorescence microscopy were used to investi gate the structural and cytochemical features of the kiwifruit (Actini dia deliciosa) pistil and to follow the pollen tube pathway after poll ination. The multicarpellary ovary is syncarpous only at the ovary lev el thus leaving 30-40 free styles on top. The fusion of the longitudin ally-folded carpels to form the syncarpous ovary forms a central paren chymatous axis, the columella, from which the ovules radiate outwards into the ovary cavity. A prominent cup shaped depression on the colume lla at the top end of the ovary, termed the pollen tube distributor cu p (PTDC) was detected. Pollen tubes from the stigma travel through the transmitting tract and enter the PTDC from where they are distributed towards the ovary. Even when pollination is restricted to two stigmas , the PTDC seems to ensure that the pollen tubes are evenly distribute d around the ovary resulting in an even distribution of seeds. This su ggested role of the PTDC which could compensate for over and under pol lination of individual stigmatic arms is another adaptive feature whic h plays a crucial role in the reproductive process of kiwifruit. The s ignificance of this structure for pollination by insects is discussed. (C) 1998 Annals of Botany Company.