Water stress and nitrogen supply affect floral traits and pollination of the white mustard,Sinapis alba(Brassicaceae)

Abstract

Changes in environmental conditions are likely to have a complex effect on the growth of plants, their phenology, plant-pollinator interactions, and reproductive success. The current world is facing an ongoing climate change along with other human-induced environmental changes. Most research has focused on the impact of increasing temperature as a major driving force for climate change, but other factors may have important impacts on plant traits and pollination too and these effects may vary from season to season. In addition, it is likely that the effects of multiple environmental factors, such as increasing temperature, water availability, and nitrogen enrichment are not independent. Therefore, we tested the impact of two key factors—water, and nitrogen supply—on plant traits, pollination, and seed production in Sinapis alba (Brassicaceae) in three seasons defined as three temperature conditions with two levels of water and nitrogen supply in a factorial design. We collected data on multiple vegetative and floral traits and assessed the response of pollinators in the field. Additionally, we evaluated the effect of growing conditions on seed set in plants exposed to pollinators and in hand-pollinated plants. Our results show that water stress impaired vegetative growth, decreased flower production, and reduced visitation by pollinators and seed set, while high amount of nitrogen increased nectar production under low water availability in plants grown in the spring. Temperature modulated the effect of water and nitrogen availability on vegetative and floral traits and strongly affected flowering phenology and flower production. We demonstrated that changes in water and nitrogen availability alter plant vegetative and floral traits, which impacts flower visitation and consequently plant reproduction. We conclude that ongoing environmental changes such as increasing temperature, altered precipitation regimes and nitrogen enrichment may thus affect plant-pollinator interactions with negative consequences for the reproduction of wild plants and insect-pollinated crops.

Seasonal variation in the response of a monoecious crop to increased temperature and fertilizers

“…reduction in the duration of visits to staminate flowers. Several studies have found that an increase in temperature (0.7 to 4°C), negatively affects the attractiveness of plants to their pollinators due to a decrease in vegetative growth, production and size of flowers, and the production and quality of nectar (Petanidou and Smets, 1996;Saavedra et al, 2003;Sato et al, 2006;Hoover et al, 2012;Liu et al, 2012;Scaven and Rafferty, 2013;Takkis et al, 2015;Mu et al, 2015;Descamps et al, 2018;Descamps et al, 2020;Akter and Klecǩa, 2022). Discrepancies with these studies may be because these have focused on plants from temperate regions (i.e., latitudes greater than 32°), where more drastic temperature changes are expected (Saavedra et al, 2003;Feeley et al, 2017).…”

“…Even when tropical plants may be less vulnerable to higher temperatures than temperate plants, studies about the response of their interactors (mutualists and antagonists) to these changes are needed to understand whether plant species are prone to persist under climate change scenarios. Moreover, further studies should examine the effects of other main drivers of global change (i.e., nitrogen deposition, increasing atmospheric carbon dioxide, water availability; see Hoover et al, 2012;Akter and Klecǩa, 2022) on main crops to have a better vision of what the future holds in terms of food security.…”

“…Particularly, the global temperature increase expected in the short term (i.e., 1.2−1.8°C from 2021 to 2040; IPCC, 2022) is expected to affect the physiology, phenology, and performance of various plants (Peñuelas and Filella, 2001;Hedhly et al, 2009;Schweiger et al, 2010;Prasad et al, 2008). For instance, it has been found that the increase in temperature rises the abortion of flowers and modifies the size of their reproductive organs (Saavedra et al, 2003;Sato et al, 2006;Scaven and Rafferty, 2013;Geŕard et al, 2020;Akter and Klecǩa, 2022), decreases nectar quantity and quality (Petanidou and Smets, 1996;Keasar et al, 2008;Mu et al, 2015;Takkis et al, 2015;Descamps et al, 2018;Akter and Klecǩa, 2022), and reduces pollen viability (Fahad et al, 2015;Descamps et al, 2018). This in turn, may decrease the number of visits and richness of floral pollinators, resulting in lower fruit and seed production (Schweiger et al, 2010;Hoover et al, 2012;Scaven and Rafferty, 2013;Kerr et al, 2015).…”

“…On the other hand, different studies have shown that the input of nutrients into the soil increase the production and size of flowers, lengthen the flowering period, and improve the quality and quantity of nectar (Lau and Stephenson, 1993;Gardener and Gillman, 2001;Muñoz et al, 2005;Burkle and Irwin, 2010;Hoover et al, 2012;Gao et al, 2021). Given that pollinators show a greater preference for plants that have a greater floral display (Mitchell et al, 2004;Akter and Klecǩa, 2022), larger flowers (Conner and Rush, 1996) or flowers with better quality in rewards (Cnaani et al, 2006); the addition of soil fertilizers should benefit the interaction of plants with their pollinators, and thus, their reproductive success (Campbell and Halama, 1993;Hoover et al, 2012;Fernandez et al, 2019). For example, plants of Ipomopsis aggregata that received fertilizer produced larger flowers and more nectar, had longer flowering periods and received more visits than plants that received no supplementary fertilizer (Burkle and Irwin, 2010), while plants of Chuquiraga oppositifolia exposed to nitrogen enrichment produced more flowers than control plants, which benefited the frequency of pollinator visits (Muñoz et al, 2005).…”

Impacts of soil nutrition on floral traits, pollinator attraction, and fitness in cucumbers (Cucumis sativus L.)

“…Here, we present one of the first studies examining the influence and interaction of nitrogen and phosphorus soil nutrients on a plant's floral traits, including reward nutritional quality, and directly testing these effects on pollinator attractiveness and plant fitness 16 , 18 , 19 , 26 . We studied the plant’s complete life cycle and measured the effects of nitrogen and phosphorus nutrient concentrations and ratios ranging from limitation to surplus.…”