Stigma-surface Esterase Activity and Stigma Receptivity in Some Taxa Characterized by Wet Stigmas

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Abstract
Stigma-surface esterase activity and stigma receptivity through a sequence of developmental stages of the pistil have been studied in four taxa characterized by having wet stigmas — Petunia hybrida, Nicotiana tabacum, Crinum defixum and Amaryllis vittata. The style is solid in the first two and hollow in the latter two taxa. In all the taxa, stigma—surface esterase could be detected in a thin surface layer (pellicle) from a very early stage of pistil development, irrespective of the presence or absence of the exudate. However, the taxa showed variation in stigma receptivity. In Petunia and Nicotiana, stigmas from pistils of all the stages supported pollen germination and tube growth. In Amaryllis and Crinum, stigmas of only the mature pistils, when the exudate is present on the stigma, supported normal pollen germination and tube growth. It is inferred that in taxa characterized by a wet stigma and solid style, the factors required for pollen germination are present from an early stage of pistil development and the exudate per se is not involved in pollen germination. In taxa characterized by a wet stigma and hollow style, however, the pellicle does not carry the factors required for pollen germination and tube growth; they appear to be present in the exudate.