VAPOR-PHASE ACTIVATION, INTRACELLULAR MOTILITY AND GERMINATION IN THETRIPORORATE POLLEN OF EPILOBIUM-ANGUSTIFOLIUM

The germinability of newly released pollen of Epilobium angustifolium in liquid medium is low, but it is enhanced by a short period in an at mosphere of 85-95% RH without access to liquid water or solutes. Durin g this period the thickened pectic layers of the intine at the germina tion apertures of the grains are eroded and prospective tube tips emer ge. Concomitantly polarised movement of organelles begins in the veget ative cells, and wall precursor vesicles (P-particles) accumulate at t he apertures. In pollen held continuously in the humid environment tra nsition to cylindrical growth follows, with the establishment of the i nverse-fountain pattern of circulation in the apical part of the tubes .