Interaction between the pollen tube and stigmatic cell wall following pollination inBrassica oleracea

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Abstract
Summary: Electron microscopic observations have revealed the stigmatic papilla wall ofBrassica oleraceaL. to be composed of several distinct layers. Measurement of the thickness of the major components of this wall has demonstrated a significant difference in cuticle thickness between the two S (incompatibility) genotypes under study. It is suggested that cuticle thickness is responsible for differences observed in the rates of pollen hydration on the stigma surface. The relevance of tins finding to the genetical control of pseudocompatibility is discussed. Unusually, the pectocellulosic component of the papillar cell wall is composed of three layers. On pollination, the outer layer detaches to permit the elongating pollen tube to pass down the papilla within the wall itself. At the base of the papilla, the tube becomes truly extracellular, growing down in the intercellular spaces between stylar parenchyma cells. Following a bud pollination, the pollen tube may even penetrate the complete cell wall and grow down the length of the cell, invested on one side by the plasma membrane and on the other by the inner face of the pectocellulosic wall. These tubes experience some difficulty in traversing the cell wall at the base of the papillar prior to entering the intercellular spaces of the style.