The increasing salinity of water in reservoirs is caused by climate change. On the other hand, an increase in salinity promotes the group species, halophytes that tolerate or need NaCl for growth. The aim of this study was to identify the response of facultative halophytes’ photosynthetic apparatus efficiency ( PE) to water salinity. The study covered the spiny water nymph ( Najas marina L.) population in four mining subsidence reservoirs. Najas marina is a facultative halophyte which means that it can occur in both fresh and salt water. This plant has the characteristics of the species invasive, such as rapid biomass growth, and wide ecological tolerance. Water salinity, described by conductivity, in the reservoirs ranged from 646 to 3061 μS∙cm ^–1. PE was expressed in terms of chlorophyll a fluorescence parameters, which were collected in situ using a Pocket PEA device. Water parameters using a YSI ProDSS probe were identified. Data analysis was performed using OJIP test and s the non-parametric Spearman’s rank test (p ≤ 0.05). The relationship between chlorophyll a fluorescence parameters and water parameters showed that conductivity, salinity, water clarity, and nitrate content statistically significantly affected PE (p <0.05). Generally, the higher salinity e.g. more than 3000 μS∙m ^–1, supports PE of facultative halophyte at the stage of optimum development in the vegetation season.

Drought significantly impacts the growth and yield of forage grasses, particularly its effect on Dactylis glomerata photosynthetic apparatus during the initial phase of development remains largely unknown. This study investigated the effects of drought on physiological parameters of various D. glomerata varieties. The seedlings obtained after seed germination under optimal and simulated drought conditions by PEG 6000 (three variants) were planted in small pots filled with garden substrate. Over a span of 42 days, the plants were initially kept well-watered (70% capillary water capacity, CWC), after which half of the seedlings from each variant were subjected to drought. This drought stress was applied during the tillering phase for 12 days. Subsequently, the plants were rehydrated (at 70% CWC) and allowed to recover for 14 days. Throughout both drought and recovery periods, measurements were taken. Leaf chlorophyll fluorescence parameters were assessed, and the JIP-test analysis was utilised to provide detailed insights into the functionality of D. glomerata photosynthetic apparatus under drought stress and post-recovery conditions. Several parameters were identified as indicative of the plants’ sensitivity to drought, such as performance indices PI _ABS and PI _tot, along with quantum yield parameters Ψ _E0, φ _E0, and φ _P0. The results highlighted that var. Minora and Tukan exhibited greater tolerance to water deficit when compared to the other varieties studied. They showed a large increases in PIABS and PItot values after drought stress as well as after the re-watering (recovery period) compared to control plants. This suggests their potential for better adaptation to drought conditions.