Changes in the Amount and Composition of Stylar Canal Exudate after Self- or Cross-pollination in Self-incompatible Lilium longiflorum Thunb.

Abstract

Pollen tubes of self-incompatible Lilium longiflorum Thunb. grow in stylar canal exudates. Changes in the amount and composition of the exudate after self- and cross-pollination were investigated.
Stylar canal exudate injected into stylar canal promoted the growth of self-incompatible 'Hinomoto' pollen tubes. The promotion was more enhanced as the amount or concentration (expressed by carbohydrate concentration) of stylar canal exudate was increased. No significant difference was found in length between incompatible pollen tubes after injection at 80 mg•ml^-1 carbohydrate concentration and cross-compatible 'Georgia' pollen tubes. Carbo-hydrate and protein contents of stylar canal exudate from self- or cross-pollinated pistils decreased as pollen tubes grew longer. Little difference between the contents of the canal exudates from self- and cross-pollinated pistils was observed. Sugar composition and molecular weight distribution of arabinogalactans which are main components of the canal exudate showed little differences by self- or cross-pollination. When pistils were administered ¹⁴C-glucose, the rates of incorporation of radioactivity into the canal exudates were not different between self- and cross-pollinated pistils. However, the amount of ¹⁴C incorporated into pollen tubes after cross-pollination was twice that fixed by pollen tubes after self-pollination. An interpretation of this phenomenon is that cross-pollination stimulated the secretion of the canal exudate more than did self-pollination.
Based on our findings, we attribute self-incompatibility in Lilium to the lack of stimulation of stylar exudate by a self pollen. This leads to an insufficient supply of canal exudate required for pollen tube growth.