科研之友
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摘要
The levels of stomata!, mesophyll and biochemical limitations in CO2 assimilation of 'Bluecrop' highbush blueberry leaves were compared at two different levels of leaf water potential. The leaf water potentials were -1.49 and -1.94 MPa in daily-irrigated (DI) and non-irrigated (NI) shrubs, respectively. The NI shrubs represented plants under moderate water stress. Mesophyll conductance (g(m)) and chloroplastic CO2 concentration (C-c) were estimated by combined measurements of gas exchange and chlorophyll fluorescence under various intercellular CO2 concentrations (C-i). Net CO2 assimilation rates (A(n)) as a function of C-c were used for calculating maximum carboxylation efficiency (alpha(cmax)) at the real sites of CO2 assimilation. Maximum A(n) (A(nmax)) from the light response curves at 400 mu mol mol(-1) air of ambient CO2 concentration (C-a) were lower in the leaves of NI shrubs than in those of DI ones. However, electron transport rates were higher in the leaves of NI shrubs than in those of DI ones. The decrease in CO2 assimilation following water stress may be caused by a decrease in g(m) rather than a decrease in stomatal conductance (g(s)) according to limitation analysis. Limitation rates by g(s), calculated at 400 mu mol mol(-1) air of C-a in A(n)-C-i curves, were not significantly different between the leaves of DI and NI shrubs. However, limitation rates by g(m) from A(n)-C-c curves were significantly higher in the leaves of NI shrubs than in those of DI ones. Maximum carboxylation efficiency (alpha(cmax)) values calculated from the A(n)-C-c curve, contrary to those calculated from the A(n)-C-i curve, were higher in the leaves of NI shrubs than in those of DI ones. Consequently, mesophyll limitation than stomatal and biochemical limitations mainly down-regulated the photosynthesis in the leaves of 'Bluecrop' blueberry shrubs during moderate water stress.
- 出版日期2012-12
