Daily Variations of Photosynthetic Efficiency of Greenhouse Tomato Plants during Winter and Spring

in Journal of the American Society for Horticultural Science
View More View Less
  • 1 Centre de Recherche en Horticulture, Pavillon de l'Envirotron, Université Laval, Québec, QC, G1K 7P4, Canada
  • | 2 Greenhouse Crops Research Center, Agriculture and Agri-food Canada, Harrow, ON, N0R 1G0, Canada
  • | 3 Centre de Recherche en Horticulture, Pavillon de l'Envirotron, Université Laval, Québec, QC, G1K 7P4, Canada

Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.

Contributor Notes

Corresponding author; e-mail: andre.gosselin@crh.ulaval.ca.
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 213 69 11
PDF Downloads 371 127 9