Temperature rise and water stress modify floral signals of bee-visited plants

« Floral signals are a key element for the interactions between plants and their pollinators. However, climate changes alter the abiotic constraints faced by plants, increasing mean temperatures and water stress events. These stresses may affect flower development and reward production, thus altering floral signals. It is well known that the plant reproductive phase is particularly sensitive to these abiotic stresses. Modification of floral signals can disrupt the plant-pollinator interactions. To estimate such changes in floral biology and interactions with pollinators, we investigated the consequences of temperature rise and water stress on plant growth, floral biology and reward production of several bee-visited species. The species were selected based on their attractiveness to pollinators and high reward production: Borago officinalis, Echium plantagineum, Echium vulgare and Impatiens glandulifera. Plants were placed for 5 weeks under three temperature regimes (21, 24, and 27°C) and two watering regimes (well-watered and water-stressed). The reproductive growth was affected by both stresses. Water stress decreased flower number per plant particularly at 24°C and 27°C. Both stresses reduced the flower size: the corolla surface of water-stressed plants at 27°C was 40% to 60% lower than the corolla surface of well-watered plants at 21°C, depending on the plant species. The decrease of these two parameters – flower number and corolla surface - resulted in a reduced floral display for pollinators. Both stresses also decreased reward production. For example, the sugar content of B. officinalis nectar decreased from 3.9 ± 0.3 mg per flower in the well-watered plants at 21°C to 1.3 ± 0.4 mg per flower in the water-stressed plants at 27°C. In this species, the total pollen quantity was not affected, but the pollen viability decreased from 79 ± 4 % in the well-watered plants at 21°C to 25 ± 9 % in the water-stressed plants at 27°C. A similar trend was observed for the other studied plants with a decrease of nectar quantity and sugar concentration and a decrease of pollen viability. Our results showed that abiotic stresses related to climate changes induce flower modifications that might most likely affect pollinator behavior. Studying the consequences on insect behavior constitutes the next step of our project. »

Affiliations

UCLouvainSST/ELI/ELIA - Agronomy

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Descamps, C., Quinet, M., & Jacquemart, A.-L. (2018). Temperature rise and water stress modify floral signals of bee-visited plants. Annual Meeting of Plant Ecology and Evolution, Meise. https://hdl.handle.net/2078.5/22763