XYLEM DEVELOPMENT IN THE GYNOECIUM OF THE APPLE (MALUS-PUMILA L) CV COX ORANGE PIPPIN

Lignification of the xylem within the carpellary bundles of apple flowers spreads acropetally from a point 900-1400 μm below the base of the locules. At the same time, another wave of lignification spreads basipetally from a point just below the stigma. The acropetal spread at first progresses more quickly, but at later stages the number of lignified xylem elements just below the stigma increases rapidly, reaching a peak just as the flower opens. This increase is very localized and the number declines greatly within only 25 % of the stylar distance below the stigma. Lignification of the xylem in the bundles serving other flower parts precedes that serving the gynoecium, and spreads basipetally from a point above the base of the locules. © 1991 Annals of Botany Company.