Stomatal responses to biotic and abiotic stress

Diversity in the ecological distribution of plant species across a vast array of environments and/or ecological niches is indicative of the adaptive capacities of individual species to maintain optimal biological functioning through the exploitation of evolved competitive advantages. This ability to exploit particular environments through morphological and/or physiological adaptation is fundamental to the ecological range of species and of particular relevance in predicting the expansion/contraction or fundamental altering of ecosystems with predicted environmental change.Elevated atmospheric carbon dioxide concentrations have been shown to alter physiological, morphological and developmental traits of extant plant species to varying degrees and often provoke acclamatory responses where plants are grown under sustained enrichment regimes over extended time periods. Despite this, contemporary evolutionary responses amongst extant plant species that coincide with modern, anthropogenically driven CO2 rise have not, as yet, been demonstrated.This thesis combines a long term free-air carbon dioxide enrichment experiment with short term growth chamber and diversity trials in order to assess the implications of moderate levels of atmospheric carbon dioxide enrichment in a semi natural European grassland system. Complementary use of these experimental protocols allows for the isolation of significant environmental effects and an assessment of their true ecological implications.Results presented here demonstrate a persistent alteration to certain key physiological traits amongst the offspring of plants exposed to long term [CO2] enrichment. Significantly these observations are not uniform across all species which indicates a differential capacity to demonstrate a heritable response to increasing atmospheric CO2 between species in this particular grassland community. Findings in this instance may have serious implications for biodiversity, ecosystem dynamics and productivity in temperate grasslands. Further, the incorporation of a diversity trial as part of this research demonstrated that investigations of evolutionary responses in the context of their biotic communities are essential although considerably more complex then studying responses to abiotic factors in isolation.