EFFECT OF SALT STRESS (NACl) ON WHOLE PLANT CO2-GAS EXCHANGE IN MANGO
Three representative days with 24 measurements for every hour a day were selected in each experiment, showing that low NaCl concentrations (15 and 30 mM) reduced A and RD six days after the treatments started. After 3 more days and an increase to 60 mM NaCl a significant reduction of A was measured compared to control plants. In another experiment NaCl-salinity reduced A in both rootstock cultivars without clear difference, but M. indica '13–1' had lower RR compared to M. indica 'Turpentine' and higher CG. No significant differences in mineral contents were measured, but M. indica '13–1' had absolute higher Na+, Cl- and Ca2+ contents in leaves. M. indica '13–1' compared directly with M. zeylanica showed clear differences. At 60 mM NaCl A was 8 μmol CO2 m-2s-1 in M. zeylanica and only 3 μmol CO2 m-2s-1 in M. indica '13–1'. In M. zeylanica a higher RR was measured. Significant lower Na+ contents were found in roots and young leaves of M. zeylanica as compared to M. indica '13–1'. The K+ contents and K/Na ratio were significantly higher in roots of M. zeylanica.
Physiological characterization of whole plant CO2 gas exchange under controlled environment conditions may be a useful tool for plant description. Data indicated only small differences in salt tolerance between M. indica '13–1' and M. indica 'Turpentine'. Promising higher tolerance may exist in M. zeylanica.