The structure of the transmitting tissue of Arabidopsis thaliana (L.) and the path of pollen tube growth

Abstract

 The compatible response in flowering plants is a complex process involving a series of cell communication events leading the pollen tube through the gynoecium to the ovule. We provide the first description of pollen tube growth in vivo in Arabidopsis thaliana. The structure and composition of the transmitting tissue of the septum are examined at the light microscope and transmission electron microscope levels. We demonstrate that once pollen tubes leave the extracellular matrix (ECM) of the central septum, they adhere to and travel along the ECM of the septum epidermis. This ECM, which surrounds the pollen tubes, is secreted through breaks in the cuticle of the septum surface. The transmitting tract ECM stains strongly for acidic polysaccharides. Monoclonal antibodies to esterified and low-esterified homogalacturonans (pectins) do not localize to this ECM. Yariv phenylglycoside and monoclonal antibodies to arabinogalactan proteins (AGPs) provide evidence that AGPs are a component of the septum epidermal ECM.