Impacts of ozone pollution on nectar and pollen quality and their significance for pollinators /

Abstract

This thesis explores the impacts of ozone pollution on the nutritional quality of nectar and pollen. We report the use of HPLC and HPIC to quantify the amino acids and carbohydrates in nectar and the development of a microwave-assisted acid hydrolysis to quantify the proteinbound amino acids available in pollen, allowing back-calculation to estimate total protein content. Utilising ten cultivars of broad bean (Vicia faba L.), exhibiting considerable variation in response to ozone, we explored what parameters are meaningful when attempting to determine the impacts of ozone (reductions in biomass, seed yield etc.) and whether these measures are consistent with the influence of the pollutant on pollen quality. We found little correlation between impacts on pollen quality and any usually-measured plant traits affected by ozone. We concluded that ozone influences pollen qualities in two ways; (i) exposure to ozone during plant growth influences the allocation of proteins to pollen, and (ii) ozone may cause direct oxidative damage to pollen once dehisced from anthers. We investigated the impact of ozone on the allocation of amino acid and carbohydrate resources to nectar and pollen, using broad bean (Vicia faba L.) as a convenient model. Plants grown in O3 and exposed to charcoal/purafil® filtered air (CFA) at flowering allocated significantly more sucrose and amino acids into their nectar than plants in other fumigation treatments. We discovered a reduction in the amount of free amino acids recoverable from the outer surface of the pollen in all treatments subject to O3 exposure, but most significant in plants maintained throughout in O3. We also found a significant shift in the proportions of amino acids in the respective ozone treatments. The final experimental thesis chapter explored the potential impact of ozone-induced changes in nectar quality on bee behaviour. Simulated ozone-induced changes in nutrient composition of nectar were employed in an olfactory conditioning assay using honeybees. Bees trained with nectar matching that of plants subject to O3 and exposed to CFA at flowering demonstrated an initially improved rate of learning, but association with reward decreased rapidly, whereas those trained with nectar matching that of plants from CFA was sustained.