Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6-tetramethyl-4-piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro. By comparing the effects of chemical scavengers and physical quenchers, we concluded that proline eliminates singlet oxygen via a physical mechanism, with a bimolecular quenching rate of ca. 1.5-4 10 6 M −1 s −1 . Our data also show that proline can eliminate superoxide in vitro in a process that is likely to proceed via an electron transfer reaction. We could also show that proline does quench both singlet oxygen and superoxide produced in isolated thylakoids. The scavenging efficiency of proline is relatively small on a molar basis, but considering its presence in high amounts in plant cells under stress conditions it may provide a physiologically relevant contribution to ROS scavenging, supplementing other nonenzymatic ROS scavengers of plant cells. | INTRODUCTIONAn important consequence of various environmental stress effects in plants is the production of reactive oxygen species (ROS), including hydroxyl radicals (OH˙), hydrogen peroxide (H 2 O 2 ), superoxide (O 2˙− ), and singlet oxygen ( 1 O 2 ). These species cause damage to proteins, lipids, and other macromolecules and inactivate important cellular functions, such as photosynthesis. Plant cells contain several ROSscavenging molecules, which are utilized to remove or inactivate harmful reactive oxygen forms. These include antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), to remove O 2˙− and H 2 O 2 , respectively, as well as low molecular mass antioxidant metabolites, such as ascorbate, α-tocopherol, glutathione. An important antioxidant metabolite is proline (Pro), which accumulates in large quantities in plant cells in response to exposure to stress effects, especially water deficit, salinity, UV radiation, and heavy metals (Meena et al., 2019; Szabados & Savouré, 2010). Apart from contributing to cellular osmotic adjustment as a compatible solute, Pro also decreases the level of various ROS forms in intact plant systems (Banu et al., 2010

Background: Traditional knowledge plays an important role in the conservation of floral diversity and is often used for the treatment of numerous diseases in local medicinal systems. Diverse cultural groups in the Himalayan regions have their own local indigenous healthcare systems, with medicinal plant applications that differ depending on geography and ecology. Therefore, it is important to understand plant ecological behavior for prioritizing conservation efforts and comprehending the impact of climate change on plant phenological traits. Methods: Ethnopharmacological data was collected through interviews and group discussions using semistructured and close-ended questionnaires from different ethnic groups i.e., Gujjar, Bakarwal, and Kashmiri. The data was subjected to hierarchical cluster analysis and ordination techniques (Principal Component Analysis) using multivariate software.Results: The present investigation documented a total of 32 plant species belonging to 31 genera in 23 families.Across the 23 families, the distribution of species was unequal, half of the species belonged to just 6 families (Asteraceae, Berberidaceae, Lamiaceae, Ranunculaceae, Solanaceae and Amaranthaceae) while the remaining half belonged to 17 families. Amongst the parts of plants, roots were the most utilized plant part with 25% of usage followed by whole plant (22%). Gastro-intestinal disorders were treated with most species (18%), followed by pulmonary infections (13%). A heat map showed two distinctly separated clusters based on the degree of intensity of flowering timing of the flora and month. Based on the conservation assessment, out 19% of all species observed fell in the Critically Endangered category of IUCN, followed by 6% in the Vulnerable category.Conclusions: This study provides the ethnopharmacological and ecological scope of the plants of the Kashmir in the northern Himalaya. There is need to develop strategies to conserve and sustainably harvest these plants in order to maintain their long-term benefits in the medicinal field.

The photosynthetic efficiency in plants is affected by salinity. Focus of this study was to observe the consequences of salinity on the rate of photosynthesis in Moringa (Moringa oleifera L.) plants. Experiment was conducted under field conditions with 3 replicates and data of treated and non-treated plants was collected accordingly. Photosynthetic rate was affected by different levels of salt stress. The change in photosynthetic was attributes were determined by OJIP and light response curve calculations by using Fluor Pen [FP 100-PS (Photon system, Czech Republic)] and DUAL-PAM-100 (Walz, Germany). Salinity stress decreased chlorophyll a fluorescence characteristic. The significant quantity of electron transport (φEo), quantum yield of primary photochemistry (φPo), proficiency per trapped excitation (Ψo) and performance index of photosystem II (PSII). Performance index (PIABS) was also declined with salinity in M. oleifera. Our results showed that electron transport rate and photosynthetic rate were inhibited by salinity in M. oleifera. However, in M. oleifera electron transport pathway of PSII was repressed and found varied in plants which are salt resistant. It was concluded that Y(I), ETR(I), Y(II), ETR(II), and Y(NA) were decreased by increasing salinity while NPQ, Y(ND), Y(NO) and Y(NPQ) increased in plants having resistance to salt stress

Singlet oxygen (1O2) is an important damaging agent, which is produced during illumination by the interaction of the triplet excited state pigment molecules with molecular oxygen. In cells of photosynthetic organisms 1O2 is formed primarily in chlorophyll containing complexes, and damages pigments, lipids, proteins and other cellular constituents in their environment. A useful approach to study the physiological role of 1O2 is the utilization of external photosensitizers. In the present study, we employed a multiwell plate-based screening method in combination with chlorophyll fluorescence imaging to characterize the effect of externally produced 1O2 on the photosynthetic activity of isolated thylakoid membranes and intact Chlorella sorokiniana cells. The results show that the external 1O2 produced by the photosensitization reactions of Rose Bengal damages Photosystem II both in isolated thylakoid membranes and in intact cells in a concentration dependent manner indicating that 1O2 plays a significant role in photodamage of Photosystem II.

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Cyanobacteria can form biofilms in nature, which have ecological roles and high potential for practical applications. In order to study them we need biofilm models that contain healthy cells and can withstand physical manipulations needed for structural studies. At present, combined studies on the structural and physiological features of axenic cyanobacterial biofilms are limited, mostly due to the shortage of suitable model systems. Here, we present a simple method to establish biofilms using the cyanobacterium Synechocystis PCC6803 under standard laboratory conditions to be directly used for photosynthetic activity measurements and scanning electron microscopy (SEM). We found that glass microfiber filters (GMF) with somewhat coarse surface features provided a suitable skeleton to form Synechocystis PCC6803 biofilms. Being very fragile, untreated GMFs were unable to withstand the processing steps needed for SEM. Therefore, we used polyhydroxybutyrate coating to stabilize the filters. We found that up to five coats resulted in GMF stabilization and made possible to obtain high resolution SEM images of the structure of the surface-attached cells and the extensive exopolysaccharide and pili network, which are essential features of biofilm formation. By using pulse-amplitude modulated variable chlorophyll fluorescence imaging, it was also demonstrated that the biofilms contain photosynthetically active cells. Therefore, the Synechocystis PCC6803 biofilms formed on coated GMFs can be used for both structural and functional investigations. The model presented here is easy to replicate and has a potential for high-throughput studies.

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