Negative Effects of Pollen Drought Stress on Floral Volatiles, Floral Nectar, Pollinator Behavior, and Seed Production in Ocimum basilicum Plants

Abstract

Ocimum basilicum is an aromatic plant belonging to the family of Lamiaceae. Many biotic and abiotic factors particularly drought stress  influences its reproduction. Drought stress can harm the pollen grains of O. basilicum plants and disrupt the production of floral volatiles,  reduce floral rewards for pollinators, decrease pollinator activity, and ultimately result in a decline in the seed set. These detrimental  impacts highlight the importance of sufficient pollen availability for the successful reproduction and survival of plant species. The  reproduction in plants is significantly impacted by drought stress, as it can directly or indirectly alter the attraction of pollinators. In this  study, the effect of drought stress in O. basilicum plants was investigated by comparing drought- with no drought-stressed plants in  order to examine various elements including: (1) nectar quantity and quality (2) pollen production (3) flower volatile emissions (4)  pollinator visitation rates from both domesticated and wild species, and (5) the plant’s' reproductive outcomes, which contributes to the  knowledge of the relationship between drought stress and pollination on O. basilicum. The planting was done in two different locations  within the Saran division of Bihar state in India, first one is Chapra town and second one is Siwan town, in June 2019. The result indicated  that plants with drought conditions, in contrast to drought free plants, produced a reduced quantity of pollen and had a decrease of the  number of flowers and the volume of nectar produced per flower. Furthermore, drought affected plants produced nectar with a lower  percentage of sucrose in relation to the total sugar content. Bees visiting rate was low compared to control plants and plants emitted  more Z-3-hexenol, C4H8O, C5H10O, and Isovaleraldehyde. Moreover, this study utilized HPLC analysis to investigate the impact of  drought stress on the floral nectar of O. basilicum plants. The findings revealed significant changes in nectar composition, highlighting  the susceptibility of plantpollinator interactions and seed production to environmental stress factors.