Effect of soil water deficit on flowers and plant-pollinator interactions of two blueberry cultivars - Arthropod-Plant Interactions
Pollination is a key ecosystem service currently threatened by multiple environmental pressures, including climate change. Drought increases plant physiological stress, reducing the resources available for reproduction and potentially affecting flower traits, mutualistic interactions and fruit production. In blueberry, previous studies have shown that post-harvest drought can reduce flower production in the following year, but its effects on plant-pollinator interactions and fruit set remain poorly understood. Here, we investigated how low water availability influences flower display size, volatile emissions, and nectar rewards, and how these potential changes affect pollinator behavior and fruit production in two insect-dependent blueberry cultivars (‘Bluecrop’ and ‘Duke’). Starting at bud break and continuing throughout flowering, half of the plants of each cultivar were exposed to controlled water deficit, while the remaining plants were well-watered. Overall, our results demonstrate that northern highbush cultivars ‘Bluecrop’ and ‘Duke’ differ in several floral traits, yet no significant interaction between cultivar and water treatment was detected, indicating that the response to water deficit was not cultivar dependent. In both cultivars, water deficit reduced nectar production, which likely decreased visitation rates by floral visitors, leading to a decline in fruit set. The solitary bee Anthophora plumipes accounted for the vast majority of visits and showed a preference for control flowers. Our results show that water deficit may influence floral traits linked with pollinator attraction and fidelity and, subsequently, impact the floral visitor behavior and fitness of highbush blueberry.
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