Additional site for pollen germination in carrot.

摘要

Studies were conducted to determine an additional site for the germination of carrot pollen. In order to analyse pollen germination as it occurs in nature, 60 flowers of Daucus carota subsp. sativus in the female phase were randomly picked up in nature and fixed in 70% alcohol. These were later scanned using the decolourized aniline blue fluorescence method. No pollen load was found on 9 gynoecia. In 6 gynoecia, the pollen-pistil interaction pathway was conventional where pollen grains were seen germinating on the stigma. However, in the remaining 45 gynoecia, pollen germination was recorded exclusively on the surface of the stylopodium. Pollen tubes were seen emerging from the pollen grains and entering the ovary. However, these were being attracted to only one of the ovules, while the other remained unfertilized. To confirm whether the pollen grains on the stylopodium affected seed set, stigmatic pollination was experimentally inhibited. The stigmas of 22-36 flowers per umbellet were clipped off during the male phase to check if fruit formation occurred. In another set of experiments, the stigmas of 30-40 flowers per umbellet were sealed with glue during the male phase for the same purpose. After 3 weeks, fruit formation was noticed. On pooling the data of the 2 experiments, an average of 32.87+or-6.45% fruit set was observed per umbellet. In the control, an average of 73.44+or-6.34% fruit was set. Based on these results, pollen germination on the stylopodium leads to fruit formation in D. carota subsp. sativus. Following these observations, 40 gynoecia of wild carrot (D. carota subsp. carota) were also scanned using the fluorescence technique. However, no such observation was recorded in the carpels of wild carrot. These followed the conventional pollen-pistil interaction pathway.