In order to evaluate morphological and physiological traits related to drought tolerance and to determine the best criteria for screening and identification of drought-tolerant genotypes, we grew two tolerant genotypes (MCC392, MCC877) and two sensitive genotypes (MCC68, MCC448) of chickpea under drought stress (25% field capacity) and control (100% field capacity) conditions and assessed the effect of drought stress on growth, water relations, photosynthesis, chlorophyll fluorescence and chlorophyll content in the seedling, early flowering and podding stages. Drought stress significantly decreased shoot dry weight, CO2 assimilation rate (A), transpiration rate (E), and Psii photochemical efficiency (Fv/Fm) in all genotypes. In the seedling and podding stages, Psii photochemical efficiency was higher in tolerant genotypes than in sensitive genotypes under drought stress. Water use efficiency (WUE) and CO2 assimilation rate were also higher in tolerant than in sensitive genotypes in all investigated stages under drought stress. Our results indicated that water use efficiency, A and Fv/Fm can be useful markers in studies of tolerance to drought stress and in screening adapted cultivars of chickpea under drought stress.

Exposure of green algae Chlorella vulgaris to short-term UV-B radiation (280 nm – 315 nm) induced several changes in the function of photosystem II (PS II) studied by means of chlorophyll fluorescence (FL) and oxygen evolving. The intensity of photosynthetic oxygen evolving intensity of algae suspension decreased in a similar way to the FL parameter values in proportion to the applied dose of UV-B radiation (0.0, 3.2, 6.4, 12.8 kJ·m-2). The correlation between photosynthetic oxygen evolving intensity and FV/FO ratio was better than that between photosynthetic oxygen evolving intensity and FV/FM. The vitality index (Rfd) in the UV-B irradiated algae strongly decreased, compared to the control, which indicates inhibition of potential CO2 fixation and cooperation between light and dark reactions of photosynthesis. It may indicate damage of Rubisco.

Diurnal measurements of photosynthetic pr ocesses, effective quantum yield of photosystem II ( F PSII ), photosynthetic electron transport rate (ETR) were done in three domi− nant species of Arctic tundra ( Silene acaulis , Dryas octopetala , Salix polaris ) in Petunia− bukta, Spitsbergen. Daily courses of net photosynthesis (P N ) were calculated from chloro− phyll fluorescence data and daily photosynthesi s evaluated. The short−term field measure− ments were carried out in summer 2009, and 2010. Fluorometric parameters ( F PSII and ETR) were measured each 5 minutes as well as microc limate characteristics of the site for 10 (2009) and 8 days (2010), respectively. In all species photosynthetic ETR was well related to incident photosynthetically active radiation a nd leaf temperature. In general, D. octopetala exhibited slightly lower ETR than the other two speci es. Estimated maximu m photosynthetic rate (P Nmax ) reached 17.6, 21.4, and 22.9 μmol CO 2 m −2 s −1 for S. polaris , S. acaulis ,and D. octopetala , respectively. Daily photosynthesis reach ed comparable values in all species, D. otopetala , however, exhibited slightly lower values than the other two species both for overcast and fully sunny days (3.9 and 13.4 mmol CO 2 m −2 d −1 , respectively). The range of daily photosynthesis for S. polaris and S. acaulis studied, reached the ranges of 4.6–6.9 and 14.6–15.2 mmol CO 2 m −2 d −1 for overcast and fully sunny day, respectively.

The depletion of natural resources such as freshwater and cropland makes it necessary to find a new solution for sustainable food production. Aquaponic systems seem to be a great alternative to traditional agriculture, however, there are still many unknowns that need to be explored. It is already known how fish stocking affects water quality in aquaponic systems, but not how it affects the plants’ growth, and especially on chlorophyll fluorescence. In this study, we examined how the density of 0, 2, 4, 8, and 16 stocking fish in five aquaria affects lettuce growth. The first tank was only a hydroponic system with plants but without fish (control). In the remaining four aquaria – 2, 4, 8 and 12 specimens of common carp fry with an average weight of 20 grams (average 8.5–33.2 g) were placed in the aquaponic growing system. Physicochemical analysis of water was conducted to determine the levels of pH, electrical conductivity ( EC), N-NO ₃, N-NO ₂, N-NH ₄, P-PO ₄, O ₂ and physiological parameters of plants (nitrogen balance index – NBI, chlorophyll content index – CCI, quantum yield – QY, flavonoid content – Flv) were analysed. The results showed that fish stocking density has different effects on plant physiological parameters, but in most cases, was insignificant. It seems that the greater number of fishes and higher density indirectly causes growth inhibition (lower photosynthetic efficiency) due to the increase of N-NO ₃ and a decrease of O ₂ in the water.

Salt stress is one of the main factors disturbing the physiology of organisms, including epigeic lichens inhabiting roadsides, due to de-icing salts used in winter seasons. The aim of the research was to study the effect of acute salt stress in various doses on the chlorophyll fluorescence parameters of chlorolichens, i.e., Cladonia furcata, C. mitis, Diposchistes muscorum, and cyanolichens, i.e., Peltigera didactyla, and P. rufescens, which naturally grow inland in the vicinity of roads. We also aimed to study changes in the photosynthetic efficiency of lichens over time and their responses to rainfall simulations in the days following exposure to salt stress to test whether liquid water supply improves photosynthetic efficiency. Salt stress led to a reduction of it in cyanolichens in most experimental groups, while in chlorolichens only treatment with 2.9-3.9M NaCl solutions significantly decreased F_V/F_M. Exposure to acute salt stress significantly affected fluorescence transient curves in all studied species. With respect to chlorolichens, a marked decrease of FM was observed and the flattened shape of the transient curves after treatment with the highest salt doses was the most apparent. Significantly greater disturbances were observed in cyanolichens in which the induction curve lost its sigmoid characteristics after treatment with solutions with a concentration greater than 0.35M. Furthermore, in all lichen species, increased values of ABS/RC and DI ₀/RC and decreases in PI _ABS, ET ₀/RC and TR0/RC as well as quantum yields and efficiencies were observed. Simulated rainfall resulted in a significant increase in the photosynthetic efficiency of chlorolichens to a level corresponding to healthy lichens almost throughout the duration of the whole experiment. On the contrary, in the case of cyanolichens, significant increases in F_V/F_M after water treatment were found only after exposure to low salt doses and, at the latest, 24 h after the stress. Although many cyanobacteria developed adaptations to survive in highly saline environments, cyanobionts present in inland lichen species seem to be highly susceptible to salt stress. We concluded that the time when rainfall occurs after exposure to salt stress is a crucial factor affecting the potential regeneration of PSII efficiency. Regeneration after rainfall is an important aspect for epigeic lichens occurring near roadsides, where, during the winter season, they are exposed to de-icing salt for a long time, and rainfall may partially compensate for their disturbances and increase their photosynthetic efficiency, enhancing the possibility of survival.

Abiotic stressors contribute to growth restriction and developmental disorders in plants. Early detection of the first signs of changes in plant functioning is very important. The objective of this study was to identify chlorophyll fluorescence parameters that change under phosphorus deficiency stress in cucumber. In this work, a trail to study the early changes caused by phosphorus deficiency in cucumber plants by analysing their photosynthetic performance is presented. Chlorophyll- a fluorescence (ChF) parameters were measured every 7 days for a period of 28 days. Measurements were made separately on young and old leaves and on cucumber fruit. Parameters that decreased during the stress were: p2G, PI _abs, PI _total, RE_o/CS _o, and TR_o/CS_o. P deficiency decreased total electron carriers per RC ( EC_o/RC), yields ( TR_o/ABS ( F_v/F_m), ET_o/TR_o, RE_o/ET_o, ET_o/ABS and RE_o/ABS), fluxes ( RE_o/RC and RE_o/CS_o) and fractional reduction of PSI end electron acceptors, and damaged all photochemical and non-photochemical redox reactions. Principal component analysis revealed a group of ChF parameters that may indicate early phosphorus deficiency in cucumber plants. Our results are used in the discovery of sensitive bioindicators of phosphorus deficiency in cucumber plants. Most JIP test parameters are linked to mathematical equations, so we recommend using of advanced statistical tools, such as principal component analysis, which should be considered very useful for stress identification. It has also been shown to be more effective in multivariate methods compared to univariate statistical methods was demonstrated.

The vitality of lichens and their growth depend on the physiological status of both the fungal and algal partner. Many epiphytic lichens demonstrate high specificity to a habitat type and hygrophilous species are, as a rule, confined to close-to-natural forest complexes. Tolerance to desiccation stress and the rate of photosynthesis activation upon thallus hydration vary between species. Analyzes of chlorophyll fluorescence and photosynthesis efficiency have been widely applied to determine the viability of lichens. The aim of this study was to determine the activation photosynthesis rate upon hydration in epiphytic lichens exposed to short-term desiccation stress and to find potential links between their activation pattern and ecological properties. The results proved that even highly sensitive hygrophilous lichens, i.e., Cetrelia cetrarioides, Lobaria pulmonaria, Menegazzia terebrata, do not exhibit any delay in the restart of the photosynthesis process, compared to mesophytic or xerophytic ones. All examined lichens achieved nearly 100% of their maximum photosynthetic efficiency just one hour after they had been supplied with a relatively small quantity of water. Moreover, the increase in photosynthesis efficiency, measured at 20-minute intervals upon hydration, started from a relatively high level. In addition, the differences in the content of photosynthetic pigments and water holding capacity between species did not affect the general pattern of activation, which is comparable across various lichens. It can be concluded that healthy hygrophilous lichens do not require long hydration time to regain a high level of photosynthesis efficiency after a short rainless period. This fact supports the idea of applying chlorophyll fluorescence analysis in the field to assess vitality of lichens and the condition of their natural habitat.