PHOTOSYNTHETIC BIOLOGY OF NATIVE AND CULTIVATED FRAGARIA

Significant genetic variability in photosynthetic processes and characteristics exist within the genus Fragaria. Understanding the photosynthetic biology of this genus is important for adapting horticulturally-important types to the cultivated environment, and for genetic enhancement of physiological processes. While complex and poorly understood, the photosynthetic biology of Fragaria is an excellent model system for physiological research. Fruit production has a major influence on photosynthetic processes, and potential limitations to productivity can be elucidated. Fruiting and deflowered plants have many vegetative, physiological and biochemical differences. Changes in structure and function of the photosynthetic apparatus of the chlorophyll (chl) spectra can be characterized and monitored using fourth derivative spectroscopy. Signals from chl at Cb630, Cb649, Ca693 and Ca684 are stronger in leaves of fruiting plants and are associated with higher rates of CO₂ assimilation (A). Ca693 is strongly correlated with chl content and is sensitive to developmental and environmental cues.

Fragaria chiloensis is a progenitor of the cultivated strawberry and has a high photosynthetic capacity. The physiological basis for this observation may be related to a number of factors including leaf anatomy and carboxylation potential. Mesophyll surface area and Rubisco levels likely play a role. Another factor may be enhanced light harvesting capacity and energy transfer through PSI and PSII. Strong activity at Cb630, Cb649, Ca684 and Ca703 in association with higher rates of A suggest that photosynthetic potential can be limited by the ATP and NADP supply which drive carboxylation. Biotic and abiotic stresses impact physiology and productivity at this level. While levels of control and genetic regulation of these processes are still open to speculation, a clearer picture is emerging by which plant carbon dynamics may be better regulated and enhanced.