Climate Change–Induced Stress Reduce Quantity and Alter Composition of Nectar and Pollen From a Bee-Pollinated Species (Borago officinalis, Boraginaceae)

Abstract

In temperate ecosystems, elevated temperatures, and drought occur especially during spring and summer, which are crucial periods for flowering, pollination, and reproduction of a majority of temperate plants. While many mechanisms may underlie pollinator decline in the wake of climate change, the interactive effects of temperature and water stress on the quantity and quality of floral nectar and pollen resources remain poorly studied. We investigated the impact of temperature rise (+3 and +6°C) and water stress (soil humidity lower than 15%) on the floral resources produced by the bee-pollinated species Borago officinalis. Nectar volume decreased with both temperature rise and water stress (6.1 ± 0.5 μl per flower under control conditions, 0.8 ± 0.1 μl per flower under high temperature and water stress conditions), resulting in a 60% decrease in the total quantity of nectar sugars (mg) produced per flower. Temperature rise but not water stress also induced a 50% decrease in pollen weight per flower but a 65% increase in pollen polypeptide concentration. Both temperature rise and water stress increased the total amino acid concentration and the essential amino acid percentage in nectar but not in pollen. In both pollen and nectar, the relative percentage of the different amino acids were modified under stresses. We discuss these modifications in floral resources in regards to plant–pollinator interactions and consequences on plant pollination success and on insect nutritional needs.

Not just flowering time: A resurrection approach shows floral attraction traits are changing over time

“…Nonetheless, it appears likely that there is a temporal increase in investment in pollinator attraction, and that this result is driven by populations at northern latitudes. Changes in floral rewards in response to climate change also align with previous findings indicating that both temperature and water availability can alter nectar volume and sugar content (Descamps et al, 2018(Descamps et al, , 2021Phillips et al, 2018) as well as pollen count and viability (Bishop et al, 2017;Descamps et al, 2021). This is the first paper to use the resurrection approach to examine the potential that traits responsible for plant-pollinator interactions may be evolving over time, concomitant to decreases in pollinator abundance and dramatic environmental changes due to a changing climate.…”

Sweet solutions: nectar chemistry and quality

“…Warming, atmospheric CO 2 and nitrogen enrichment have complex interactive (and sometimes antagonistic) effects on nectar sugars and amino acids of pumpkin Cucurbita maxima [ 135 ]. Temperature rise and water shortage have varied effects on floral resources of Borago officinalis : both stresses decrease nectar volume and thus total sugars, both increase the total nectar amino acids and change their composition, but pollen is more affected by high temperature than by drought [ 88 ]. For a review of the metabolic changes occurring in flowers in response to climate change, see [ 136 ].…”

“…Pollen is a potential source of nectar amino acids, especially as it is far richer in these compounds, e.g. 1000× higher than in nectar on a per flower basis [ 88 ]. Contamination with pollen falling into nectar could lead to high levels of proline and other amino acids [ 89 , 90 ].…”

Climate Change Impacts on Broussenetia papyrifera Pollens - Metabolome Investigations and Prospects of Allergy Prevalence

“…The morphological studies and biochemical analysis of pollens through FTIR show that environmental variables (temperature and precipitation), have significant effect on pollen proteins and lipids contents. Such climate roles affecting pollens biochemical composition have been verified in several studies [33,45–48], and increasing prevalence of pollen allergenicity [49]. Findings of this research are unique which may help in determining the temperature effects on activation of reactive oxygen species (ROS), heat shock proteins (HSP), and oxidative stress mechanisms in pollens.…”