3.1 Chlorophyll a fluorescence induction and JIP test
We used a JIP-test (Strasser et al., 2004) to unravel the effect of salt
stress on most of PSII parameters in both SV and SA .
Results depicted in Figure 2 were derived from the fast phase Chla fluorescence induction curve, i.e. the OJIP curve. Salt stress
treatment experiments show that, for SV , even moderate NaCl
concentration (50 mM) increased the Fo level (data not shown) and the
J-test of OJIP induction curves (data not shown). However, SAshowed no/or slight difference in the OJIP induction curves for moderate
(250 mM) and high (550 mM) NaCl concentrations compared to the control
without NaCl. Therefore, the function of PSII was not affected forSA ; however, it was strongly inhibited and/or damaged forSV even at relatively low NaCl concentration (50 mM). To study in
detail the effects of NaCl on PSII in these two species, we evaluated
the PSII parameters using the JIP-test (Fig 1, Table S1; Strasser et
al., 2004). The JIP-test was evaluated from SV (A, B and C) andSA (D, E and F) exposed for 5 (A, D), 10 (B, E) and 15 days (C,
F) to different NaCl concentrations. Herein, we observe that after 5
days of exposure to 100 mM NaCl, PSII parameters showed apparent change
in SV (Figure 2A, green spider). The salt effect became more
pronounced after 10 days of exposure to salt at either 50 or 100 mM
(Figure 2B, red and green spiders). However, for SA , the
deviation in the PSII parameters calculated with JIP-test was much less
and observable only for high NaCl concentration (550 mM) after 10 and 15
days’ exposure (Figure 2E-F, black spider). Therefore, PSII of SVwas more sensitive to salt stress, as compared to SA .