Photosynthesis during progressive water stress in interior spruce (Picea glauca (Moench) Voss): Physiology and protein composition

lthough the stress responses of conifers have been extensively investigated in terms of growth and survival, the ramifications for the perennial photosynthetic apparatus are not well characterized. Coping with excess radiation is particularly important for conifers because the structurally expensive needles usually support multiple seasons of photosynthesis, surviving a range of conditions limiting carbon dioxide fixation. This thesis represents the first detailed characterization of a coordinated set of photosynthetic responses to progressive water stress by young interior spruce (Picea glauca (Moench) Voss X P. engelmanni Parry hybrid complex). Analysis of photosynthesis at the tissue and thylakoid membrane levels revealed a pattern of down-regulation that corresponded generally to that described for other species; however, it differed in that protective mechanisms were initiated during a moderate level of stress.;As water potentials declined, an integrated repertoire of mechanisms to cope with excess light energy unfolded. As mild water stress developed at water potentials below ;Details of the thylakoid response to water stress were obtained by immunoquantification of proteins using antibodies to two of the oxygen-evolving enhancer proteins (OEE1 and OEE2), the D1 reaction centre protein, cytochrome...