## 3 Results and Discussion
### Changes in OJIP Transients after Drought and Recovery
However, it has been recently reported that stabile F\({}_{0}\), in combination with stable TR\({}_{0}\)/RC (Figure 2c), as observed in kale, reflects constant trapping by active RCs that are able to reduce Q\({}_{\text{A}}\)[64]. The energetic connectivity between PSII complexes is an important feature for evaluating specific energy fluxes, and plants with higher connectivity utilize light energy more efficiently than plants with lower connectivity [86]. The connectivity parameter (\(p\)) is related to the initial phase of Chl transients and can be used to estimate the redox state of PSII electron acceptors [91] and the PQ pool [92]. A low connectivity between PSII units lowers the excitation pressure and thus protects PSII in stressful conditions. Our investigation revealed a significant increase in \(p\) only in white cabbage after drought stress compared to the control, while recovery-induced connectivity dropped to the control value (Figure 3f). Increased PSII connectivity was also reported in young grapevine leaves [93] as well as in _Phalenopsis  
Figure 2: Spider plots represent selected JIP-test parameters that characterize PSII functioning in three _Brassica_ seedlings: Chinese cabbage (**a**), white cabbage (**b**) and kale (**c**), subjected to drought followed by recovery. Each dataset is normalized to the respective controls (watered seedlings) separately for each variety (control = 1). Asterisks (*) signify differences between the treatments and the corresponding control, while double-asterisks (***) represent significant differences between both the control and recovery at \(p\leq 0.05\) (ANOVA, HSD). plants at low light conditions [86]. Even though the F\({}_{0}\) increased, the positive L band (Figure 1g) in drought-stressed white cabbage suggested the lower connectivity of PSII units. However, an increase in the connectivity parameter suggested a possible defense mechanism that prevents the overreduction of the PQ pool and thus lowers the damage to PSII [37]. It was suggested that S\({}_{\text{m}}\), together with PI\({}_{\text{total}}\) (Figure 2), could reflect the vitality of the plants subjected to certain environmental stress [94]. The S\({}_{\text{m}}\) parameter describes the normalized total area above the OJIP curve, reflecting multiple-turnover events. It is also an equivalent measure for the number of electrons transported by PSII to reach the maximum fluorescence intensity and close all RCs [94]. There was a decrease in S\({}_{\text{m}}\) in Chinese and white cabbage (Figure 3b) upon the drought, while in kale, there was no difference compared to the control. After recovery, the S\({}_{\text{m}}\) values in all varieties reached the control values. The decrease in S\({}_{\text{m}}\) upon drought, as well as the positive H band (Figure 1d,i), suggested that Q\({}_{\text{A}}\) could be reduced but not re-oxidized, since it cannot perform multiple turnovers as fast as the control seedlings due to the limited electron transport [95; 96]. The strength of the inner factors that endorse reactions in PSII is described as the SFI or the structural and functional index [44; 64]. Drought induced a decrease in SFI in Chinese and white cabbage (Figure 3c) compared to the control. While the SFI increased to the control values in Chinese cabbage after recovery, in white cabbage, the SFI remained as low as it was in drought-stressed seedlings. Various stressful conditions, such as salinity [97], PEG\(-\)induced drought stress, and salt stress [98; 99; 100], provoked changes that caused the instability of photosystems.