Water stress reduces flower and seed production in wild mustard plants

Rebecca J. Höfer, Tina Lindner, Manfred Ayasse, Jonas Kuppler

This is a plain language summary of a Functional Ecology research article which can be found here.

Climate change will lead to reduced precipitation, which can cause a water deficit in the soil, leading to water stress in plants. It is known that water stress in plants alters floral characteristics such as morphology, phenology or floral scent. These changes, in turn, can affect the attractiveness of plants to pollinators, likely resulting in reduced pollen transfer and pollination, and consequently less seed production. On the other hand, water shortage can reduce the availability of resources that plants need to produce and maintain flowers. This results in fewer flowers produced per plant and reduced seed set. However, it is not well known which of the two aspects has a stronger impact on the reproductive success of plants.

Photo of a Sinapis arvensis individual in the drought-stressed treatment (credit: Rebecca Höfer)

In this study, we manipulated water availability ranging from daily irrigation to several days without irrigation. We then measured various floral characteristics such as floral scent, flower size, flowering time and reward quantity (i.e. pollen and nectar), observed flower visitors, and counted the number of visits to each plant individual. After the flowering season, we harvested the ripe seeds as an indicator of reproductive success. We found that plants suffering from water deficit produce fewer flowers, which directly resulted in reduced fruit and seed production. Furthermore, we found that the number of flowers visited per day was reduced when plants had a shorter flowering period. The fewer flowers of a plant visited per day, the lower the seed mass, as flowers were not pollinated. However, this effect of flower visitation on seed production was weaker than the overall reduction in flower production per plant. To conclude, our results indicate that total flower production is more important for plants’ reproductive success than pollinator visits, at least in this generalist plant species.


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