tailieunhanh - Báo cáo lâm nghiệp: "Effects of a calcium deficiency on stomatal conductance and photosynthetic activity of Quercus robur seedlings grown on nutrient solution"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài: "Effects of a calcium deficiency on stomatal conductance and photosynthetic activity of Quercus robur seedlings grown on nutrient solution. | 325 Ann Sci For 1996 53 325-335 Elsevier INRA Original article Effects of a calcium deficiency on stomatai conductance and photosynthetic activity of Quercus robur seedlings grown on nutrient solution M Ridolfi1 o Roupsard 2 JP Garrec 1 E Dreyer 2 1 Équipe pollution atmosphérique 2 Équipe bioclimatologie et écophysiologie unite d ecophysiologie forestiere Centre de Nancy Inra 54280 Champenoux France Received 23 November 1994 accepted 29 June 1995 Summary The effects of a calcium deficiency on stomatai functions and photosynthesis were investigated in Quercus roburseedlings grown on a nutrient solution. A severe calcium deficiency did not perturb stomatai reactivity to abscisic acid and stomatai aperture in darkness was only slightly increased. On the other hand stomatai conductance under full light and net co2 assimilation rates decreased to one-half of the controls. A slowdown of stomatai opening during dark-light transitions was detected in the deficient leaves. Low Ca2 availabilty could reduce the light activation of chloroplastic enzymes involved in organic osmoticum production in the guard cells. The reduction of net co2 assimilation was associated with a maintenance of the co2 mole fraction in the substomatal spaces and with a stability of the photochemical efficiency of photosystem II PS II in dark-adapted leaves. Combined measurements of gas exchange and photochemical efficiency allowed the computation of the co2 mole fraction at the site of carboxylation in the chloroplast which decreased significantly in the Ca-defi-cient leaves. This result suggests that a lower co2 availability at the carboxylation site was the major factor limiting co2 assimilation under calcium deficiency. calcium deficiency stomata photosynthesis chlorophyll fluorescence Quercus Correspondence and reprints Abbreviations A net co2 assimilation rate pmol rrr2 s1 gc g . stomatai conductance to co2 and to water vapour pmol nr2 S 1 Cj Cc co2 mole fractions in the substomatal spaces and in