Stigma receptivity in comfrey (Symphytum officinale L.) during the course of anthesis

Abstract

Timing and duration of stigma receptivity in comfrey (Symphytum officinale L., Boraginaceae), a species with a dry-type stigma, were studied using two methods based on enzymatic activity (Peroxtesmo Ko and Perex tests) as well as on observations of pollen germination in hand-pollinated flowers of various stages. Moreover, structural changes of stigmatic tissue in relation to stigma receptivity were noted. In comfrey flowers the receptivity period lasted about 4-5 days. It started at the time of flower opening but full receptivity was concomitant with pollen exposure. Flowers at the final life stage did not show restricted receptivity. The stigma was covered with short, unicellular papillae. With the beginning of receptivity, papillae arrangement loosened. Receptivity only occurred at the basal part of the papillae. Germination of pollen grains started 3 hours after pollination. The results obtained with the Peroxtesmo Ko receptivity test were in line with the test for pollen germination. The Perex test wa...