Pseudo-self-compatibility in Ultraviolet-irradiated Plants of Primula Acaulis (‘pin’ morph)

Apoplastic peroxidase distribution in transmitting tissue of the stylar ‘neck’ was investigated using the DAB cytochemical reaction applied to electron microscopy in non-, self- and cross-pollinated pistils of Primula acaulis (‘pin’ morph) exposed or not to ultraviolet (u.v.) irradiation. In non-irradiated flowers, apoplastic peroxidase activity, which is present in non-pollinated pistils, is increased by self-pollination, whereas cross-pollination causes its disappearance from the central portion of the transmitting tissue. Apoplastic peroxidases localized in the central portion of the transmitting tissue are supposed to play a role in the predisposition of the pistil to reject incompatible pollen tubes and in the rejection mechanism itself. Pistil irradiation with u.v., which induces pseudo-self-compatibility, modified the aforementioned apoplastic peroxidase distribution. Shortly after u.v. irradiation of nonpollinated styles, apoplastic peroxidase activity was absent from the central portion of the transmitting tissue; some hours later peroxidase activity was restored, and 40 h after treatment, the ‘normal’ peroxidase distribution was observed. Our data suggest an u.v.-induced temporary removal of the ‘predisposition for incompatible pollen tube rejection. Moreover, soon after irradiation, the usually observed peroxidase production due to self-pollination was inhibited. Pseudo-self-compatibility, observed when self-pollination was carried out immediately after u.v. irradiation, was due to incompatible pollen tube elongation in a transmitting tissue devoid of apoplastic peroxidases and hindered in the rejection mechanism. However, pseudo-self-compatible pollen tube growth was not accompanied by the dramatic changes in transmitting tissue ultrastructure observed after compatible cross-pollination. The data indicate that, even if incompatible pollen tubes are not ‘rejected’, they are still ‘recognized’ and hindered in their absorption of cellular reserves from the transmitting tissue.

The formation of the tryphine coating the pollen grains of Raphanus , and its properties relating to the self-incompatibility system

The tryphine that coats the pollen grains of Raphanus is tapetally synthesized and is composed of a fibro-granular and a lipidic component. The fibro-granular material is proteinaceous and is secreted by cisternae of the endoplasmic reticulum. The lipidic component is derived, mainly, from degraded elaioplasts. The fibro-granular material is applied to the pollen exine first, followed by the lipidic mass. The tryphine condenses during the final stages of pollen maturation and dries down to form a thick, highly viscous coating. The major part of the condensation appears to result from dehydration. The tryphine, extracted from the pollen by a centrifugal method and mounted in a membrane, appears to be capable of penetrating the outer layers of a stigma of the same species and, if the pollen from which it was derived is incompatible with respect to the stigma, the stimulation of the production of the callosic reaction body in a manner similar to an incompatible pollen tube. It is proposed that, in Raphanus , substances responsible for the initiation of at least two stages in the self-incompatibility system are held in the tryphine.