Reproductive biology of Withania somnifera (L.) Dunal.

摘要

The morphological and functional characteristics of flowers contributing to the reproductive success in AGB002, a wild morphotype of W. somnifera collected from Rajasthan, India, were studied. Pollen transfer experiments were also conducted to investigate the effects of pollen source on fruit set, seed set and seed germination. The treatments were autogamy (pollination with pollen from the same flower), open pollination and xenogamy (pollination with pollen from the cultivated morphotype AGB025, followed by bagging). Synchronous stigma receptivity, anther dehiscence, and the close proximity of anthers and stigma predisposed this species to autogamy. AGB002 exhibited a predominant self-compatible nature. Autogamy and open pollination resulted in high fruit set (81.83+or-1.94 and 86.66+or-1.74%), whereas xenogamy resulted in a very low fruit set (3.59+or-0.85% on average). Seeds as a result of crossing were also characterized by poor germination (approximately 8-26%). Fruit set, seed set and seed germination were greater when AGB002 was used as the pollen source. Pollen viability was high (90.5+or-0.52%) during the peak flowering season (April-June), but was low (80-83% by acetocarmine test, and 65-70% by TTC test) during the post-monsoon season (September). In AGB-025, pollen viability was high (83.5+or-0.80%) during peak flowering (February-May) and was reduced (71-75% by acetocarmine test, and 61-64% by TTC test) during sporadic flowering in September. The pollen grains remained viable for 24 h under field conditions and for 3-5 days when stored under low temperatures (10 degrees C). The high pollen load on the stigma and stiff pollen competition within a flower, with approximately 817 pollen grains available for siring one ovule, greatly reduced the possibility for cross pollination.