RELATIONSHIP BETWEEN PHOTOSYNTHESIS AND RESPIRATION IN GRAPEFRUIT AND KUMQUAT LEAVES

Carbon net balance is determined by the amount of CO₂ that pass in and out by stomata and it affects the biomass production that differs between species because of the photosynthetic and respiratory rates.
With this aim two species of citrus, Fortunella japonica (Thunb.) Swingle and Citrus paradisi Macf., with differences in canopy and fruit size and phenological phases, were compared.
Gas exchanges were measured on the leaves in situ in sunlight to determine CER (CO₂ exchange rate) and in darkness to determine the respiration rate and gross photosynthesis was calculated.
At the same PAR (Photosynthetically Active Radiation) and VPD (Vapour Pressure Deficit) conditions grapefruit leaves, larger and darker green than kumquat ones, showed higher CER. Respiration rates, despite the comparison were carried out on such different leaves, resulted similar between the species, so that carbon net balance resulted better in grapefruit than in kumquat.
Furthermore, CO₂ respiratory release monitored during blooming was markedly higher in both species.

XXVI International Horticultural Congress: Citrus and Other Subtropical and Tropical Fruit Crops: Issues, Advances and Opportunities

C. Germanà, .A. Continella, E. Tribulato

citrus, gas exchange, reflectance, fluorescence

https://doi.org/10.17660/ActaHortic.2004.632.13