Effects of Light and Temperature Parameters on Net Photosynthetic Carbon Dioxide Fixation by Whole Plants of Five Lupin Species ( Lupinus albus L., Lupinus angustifolius L., Lupinus luteus L., Lupinus mutabilis Sweet. and Lupinus polyphyllus Lindl.)

Abstract

Net photosynthetic CO uptake by whole plants of five lupin species 2 ( Lupinus albus L., Lupinus angustifolius L., Lupinus luteus L., Lupinus mutabilis Sweet. and Lupinus polyphyllus Lindl.) was measured and modelled in laboratory conditions by an infrared gas analyser at six levels of photosynthetic photon flux density (PPFD: 0, 176, 352, 528, 704 and 880 w mol m -2 s -1 ) and four temperatures (5, 17, 22 and 29°;C). Measured net photosynthetic CO 2 uptake for all lupin species in all experimental conditions was 10.34 mg CO 2 dm -2 h -1 with a standard deviation ( - SD) of 10.24 and standard error ( - SE) of 0.71 mg CO 2 dm -2 h-1 . The mean value of net photosynthetic CO 2 uptake in all experimental conditions was 9.86 for L. albus , 12.71 for L. angustifolius , 10.92 for L. luteus , 7.77 for L. mutabilis and 10.04 CO 2 dm -2 h -1 for L. polyphyllus . A hyperbolic equation was formulated to illustrate the relationship between light and temperature as independent variables and net photosynthetic CO 2 fixation as the dependent variables ( r 2 =0.91). At temperatures from 17.1 to 20.1°;C and level of PPFD of 880 w mol m -2 s -1 the maximal net photosynthesis varied from 25.0 to 27.0 mg CO 2 dm -2 h -1 depending on species (25.0 for L. albus , 26.0 for L. angustifolius and L. luteus , 27.0 for L. mutabilis and 26.7 for L. polyphyllus ). The differences in net photosynthetic CO 2 fixation were more clearly observed at low temperatures (9.2–;12.5°;C) and at a low level of PPFD (220 w mol m -2 s -1 ), and varied from 9.1 to 12.2 mg CO 2 dm -2 h -1 ( L. albus 9.1, L. angusti folius 10.6, L. luteus 11.0, L. mutabilis 12.2 and L. polyphyllus 12.0). It is concluded that the response of net photosynthetic CO 2 fixation to parameters of light and temperature can be used in the ecological description of lupin species diversity. Future studies are needed to clarify this response at both the cellular and molecular levels.