Adaptive Significance of the Sculptured Exine of Pollen

Abstract

IT has been widely accepted among botanists that pollen derives nutrients from the surrounding tapetal cells as a consequence of their lytic degeneration, but recent evidence has suggested that in Tradescantia at least, the tapetum does not degenerate as early as previously supposed^1–3. In this plant the tapetal cells reorganize to form a plasmodium which engulfs each pollen grain in a vacuole. At first there is no close association between the exine and the tonoplast of these vacuoles, but as the anther matures an intimate association develops. The tapetal tonoplast expands and comes to line the interbacular cavities closely, greatly increasing the area of membrane which invests the microspore.