Structure and cytochemistry of the stigma and pollen-pistil interaction in Zephyranthes

Abstract

The stigma in Zephyranthes candida and Z. citrina is of the dry type with a continuous cuticle-pellicle. In some papillae, however, the terminal portion of the cuticle-pellicle is lifted upwards and occasionally even disrupted by the accumulation of a secretion product below it. Both non-specific esterases and acid phosphatases are present on the stigma surface. The style is solid with a central core of transmitting tissue which has conspicuous intercellular spaces containing a matrix that includes proteins, polysaccharides and pectic substances. Zephyranthes citrina is self-compatible while Z. candida is self-incompatible. Followng incompatible pollination in Z. candida, pollen germination is normal but pollen tube growth is inhibited at the junction of the stigma and style. Self-incompatibility can be overcome by bud pollination. Protein synthesis is necessary for pollen germination in both species. Concanavalin A binds to the stigma surface of both species, but does not affect pollen tube penetration in Z. candida. In crosses between the two species typical unilateral incompatibility is observed when Z. candida is used as the pistillate parent.