Pectin dynamic and distribution of exchangeable Ca2+ in Haemanthus albiflos hollow style during pollen–pistil interactions

Abstract

In this report, the localization and spatial distribution of two categories of pectin, high and low methylesterified, on the background of dynamic in loosely bound calcium (Ca(2+)) in Haemanthus hollow style were studied before and after pollination. In the style transmitting tract of unpollinated pistil, mainly high-methylesterified pectins were present, both in the transmitting tract epidermis and in the style canal. After pollination, an increase in the level of two investigated categories of pectin was observed, but the amount of high-methylesterified one in each period of time analyzed was permanently higher. Locally, in the regions of the style canal penetrated by pollen tubes, process of pectin de-esterification was initiated. However, pollination caused an increase of loosely bound Ca(2+) level in the style transmitting tract, this process appears to be not linked with pectin de-esterification and possible Ca(2+) release after the lysis of Ca(2+) cross-linked de-esterified pectin. Instead, it seems to be based on Ca(2+) exocytosis from the transmitting tract epidermis cells providing a source of Ca(2+) for pollen tubes growing in Haemanthus hollow style.