## 3 Results and Discussion
### Changes in OJIP Transients after Drought and Recovery
White cabbage also showed a positive H band (Figure 1i), but it was more pronounced in drought-stressed seedlings than it was in re-watered ones. Drought stress induced a reduction in the PQ  
Figure 1: Shapes and amplitudes of OJIP transient curves determined in three _Brassica_ seedlings after exposure to drought and subsequent recovery are shown as kinetics of relative variable fluorescence Vt and as difference kinetics \(\Delta\)VOP (**a,f,k**). Difference kinetics \(\Delta\)Vt for the individual bands L (**b,g,l**), K (**c,h,m**), H (**d,i,n**), and G (**e,j,o**) are plotted at different time ranges. The O, J, I, and P steps are indicated in Vt curves. pool size, causing a faster reduction in PQ in all three _Brassica_ crops. Upon recovery, the size of the PQ pool changed from smaller to bigger at different rates for three _Brassica_ varieties. The reduction rate of the PSI acceptor side from the PQ pool is shown as a G band, and it depends on the available NADP\({}^{+}\) molecules [37; 75]. Chinese cabbage showed a positive G band in both drought-stressed and recovered seedlings (Figure 1e), while drought-stressed kale (Figure 1o) showed a positive amplitude that returned to control values after recovery. However, in white cabbage (Figure 1j), both curves were shown to be negative. A positive G band indicated a decrease in the PSII acceptors pool, accompanied by reduced electron transport and a subsequent reduction in the PSI reduction rate [75]. On the other hand, the negative G band seen in white cabbage was suggested to be a compensatory mechanism developed by plants exposed to inadequate and stressful conditions [37; 77]. In such conditions, the number of available NADP\({}^{+}\) molecules increased, which, in turn, increased the activity of PSI [37; 75]. Additionally, it was recently suggested that drought-induced changes in the I-P amplitude, corresponding to the G band, could be associated with the build-up of the cyclic electron flow [78], which would protect PSI from the overreduction of its acceptor side. by drought, resulting in lower electron feeding from OEC [61]. It was also recently suggested that an increase in the named parameters due to a prolonged exposure to stress could diminish the energetic connectivity by detaching light-harvesting antennae from PSII [37]. In addition, the decrease in ET\({}_{0}\)/RC upon the drought exposure, accompanied by the increase in ABS/RC and TR\({}_{0}\)/RC, suggested the transformation of active RCs into dissipative ones [61; 87]. This is corroborated by the increased DI\({}_{0}\)/RC in drought-stressed seedlings, suggesting that this could be a useful protective mechanism in drought-stressed seedlings of white cabbage. Moreover, the unchanged RE\({}_{0}\)/RC indicated low pressure on PSI, preventing its overreduction [83]. Since Chinese cabbage recovered most of the parameters to the control level, it could be assumed that primary reactions were reversibly downregulated and that all trapped energy could be efficiently utilized in the electron transport chain. In white cabbage, however, the damages were more severe, as judged from the high values of energy fluxes, even after recovery, suggesting that white cabbage was the most drought-sensitive variety compared to Chinese cabbage and kale. Minimal fluorescence (F\({}_{0}\), Figure 3a) was shown to be a reliable indicator of the PSII state during stress [88]. An increase in F\({}_{0}\) was observed in Chinese and white cabbage after the drought, while kale showed no significant change. Recovery induced a decrease in the parameter to the control level in Chinese cabbage; however, in white cabbage, the value remained as high as in drought-stressed seedlings. As a parameter associated with the primary photochemistry of PII, its increase suggests that plants subjected to stressful conditions downregulate PSII activity [70; 89]. It was reported recently that the increase in F\({}_{0}\) was the result of disconnected light harvesting antennae from the PSII core complex in chilling stressed sugarcane [90].