Autecological studies on Audouinia capitata. 3. Pollination

Autecological studies on Audouinia capitata (Bruniaceae). 3. Pollination biology
J.H. de Lange C. Boucher J.J.A. van der Walt
1993 South African Journal of Botany 59: 135-144
DOI:10.1016/S0254-6299(16)30747-5

Flower production in Audouinia capitata is highest during the first post-fire season. Self-pollinated flowers produced a mean of only 0.8% fruits bearing seeds. This seed set was increased 17-fold by natural insect-mediated cross-pollination. Hand cross-pollination induced an approximately 5-fold increase in seed set when compared to natural cross-pollination. Germination and initial pollen tube growth are normal following self- as well as cross-pollination. Selfing, however, is characterized by abnormal pollen tube growth at the stylar base, resulting in cessation of growth except in the case of occasional pollen tubes. By one week after cross-pollination, pollen tubes have penetrated the egg apparatus. Average in vitro germination of pollen and frequencies of small underdeveloped microspores in 20 populations varied from 2.5 to 28.4% and from 2.0 to 23.7%, respectively, with large interplant variations within populations in both germination (0 – 79.6%) and underdeveloped microspores (0 – 61.0%). The prevalence of non-viable pollen and insufficient insect-mediated transfer of pollen between the plants which have an insignificant ability to produce seed following self-pollination, are limiting factors in reproduction.

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"Fires induce markedly increased flower production which gradually decreases with time after fire. The flowering season is protracted, extending from May to the end of September in the Cape of Good Hope Nature Reserve. Receptive flowers in the larger populations were present for approximately 3 months and on individual plants from approximately 3 weeks to 2 months."

"A. capitata has a limited ability to set seed in the absence of cross-pollination. A 17-fold increase in seed production was evident following natural insect-mediated cross-pollination. The use of pollen with high in vitro germination capabilities in hand cross-pollination, resulted in an approximately S-fold increase in seed set compared to natural cross-pollination. Even in the absence of insect activity, considerable self-pollination was evident, the extent depending on the difference in height between stigma and anthers, with averages ranging from 11 to more than 100 pollen grains per stigma for the different flower types investigated. "

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Publicado el junio 16, 2022 07:29 TARDE por tonyrebelo