INTERRELATIONSHIPS BETWEEN CYTOPLASMIC CA2-MEMBRANE CONDUCTANCES DURING COMPATIBLE AND INCOMPATIBLE POLLINATIONS OF BRASSICA-NAPUS PAPILLAE( PEAKS, POLLEN HYDRATION AND PLASMA)

We have investigated Ca2+-involving cell signaling, plasma membrane po tentials and conductances and callose formation during early stages of pollination of papillae of Brassica napus. Using fluorescence imaging of calcium green-1, we found that application of a range of pollen ty pes and controls all rapidly produced small localized peaks in papilla r cytoplasmic [Ca2+]. This response was more frequent in compatible th an incompatible interactions and was correlated with subsequent hydrat ion of the applied pollen grains, indicating that it may be a differen tial prerequisite of the compatible signaling pathway leading to succe ssful pollinations. In contrast, a slight trend to increased plasma me mbrane conductance (but with no indications of action potential-like r esponses) and also callose deposition in papillae adjacent to pollen g rains followed pollination in both SC and SI interactions, indicating that alterations in plasma membrane permeability and callose depositio n during early phases of pollination are not primary determinants of t he fate of attempted pollinations.