Assessment of stigma receptivity via papillar integrity in Kigelia pinnata (Bignoniaceae)

Abstract

The stigma of Kigelia pinnata is spathulate, wet and sensitive to touch. Consisting of two flaps or folds, the inner surface of these stigmatic flaps is papillate. Covered by a prominent papillar zone, each papilla contains lipid and phenolic deposits which remain entrapped below the thick cuticle till the stigma attains receptivity. Gradual unfolding of stigmatic flaps; about 1 h post anthesis, marks the beginning of stigma receptivity. Reaching a peak at 24 h after anthesis, the stigma remains receptive for 48 h. Papillae gradually lose turgidity after 72 h post anthesis and liberate their contents into the outside medium. During this time, stigma receptivity declines sharply as can be made out from the germination of only 10% pollen. Thereafter, none of the pollen deposited on the stigma germinates. The papillar phenology exhibits a close coordination with stigma receptivity indicating that both the processes are proportionately related to each other. Therefore, evaluation of papillar integrity can be used as a quick method to check stigma receptivity in K. pinnata.