Ecophysiological response of Lippia gracilis (Verbanaceae) to duration of salt stress

Water stress modulates terpene biosynthesis and morphophysiology at different ploidal levels in Lippia alba (Mill.) N. E. Brown (Verbenaceae)

Monoterpenes are the main component in essential oils of Lippia alba. In this species, the chemical composition of essential oils varies with genome size: citral (geraniol and neral) is dominant in diploids and tetraploids, and linalool in triploids. Because environmental stress impacts various metabolic pathways, we hypothesized that stress responses in L. alba could alter the relationship between genome size and essential oil composition. Water stress affects the flowering, production, and reproduction of plants. Here, we evaluated the effect of water stress on morphophysiology, essential oil production, and the expression of genes related to monoterpene synthesis in diploid, triploid, and tetraploid accessions of L. alba cultivated in vitro for 40 days. First, using transcriptome data, we performed de novo gene assembly and identified orthologous genes using phylogenetic and clustering-based approaches. The expression of candidate genes related to terpene biosynthesis was estimated by real-time quantitative PCR. Next, we assessed the expression of these genes under water stress conditions, whereby 1% PEG-4000 was added to MS medium. Water stress modulated L. alba morphophysiology at all ploidal levels. Gene expression and essential oil production were affected in triploid accessions. Polyploid accessions showed greater growth and metabolic tolerance under stress compared to diploids. These results confirm the complex regulation of metabolic pathways such as the production of essential oils in polyploid genomes. In addition, they highlight aspects of genotype and environment interactions, which may be important for the conservation of tropical biodiversity.

The Effects of Irrigation Water Salinity on the Synthesis of Photosynthetic Pigments, Gas Exchange, and Photochemical Efficiency of Sour Passion Fruit Genotypes

The objective of this study was to evaluate the synthesis of photosynthetic pigments, gas exchange, and photochemical efficiency of sour passion fruit genotypes irrigated with saline water under the conditions of the semi-arid region of Paraíba state, Brazil. The experiment was conducted at the experimental farm in São Domingos, PB. A randomized block design was adopted, in a 5 × 3 factorial scheme, with five levels of electrical conductivity of irrigation water-ECw (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1)-and three genotypes of sour passion fruit (Gigante Amarelo-'BRS GA1'; Sol do Cerrado-'BRS SC1'; and Catarina-'SCS 437'. The increase in the electrical conductivity of irrigation water negatively affected most of the physiological characteristics of the sour passion fruit at 154 days after transplanting. Significant differences were observed between sour passion fruit genotypes when its tolerance was subjected to the salinity of irrigation water. There was an increase in the percentage of damage to the cell membrane with the increase in the electrical conductivity of irrigation water, with maximum values of 70.63, 60.86, and 80.35% for the genotypes 'BRS GA1', 'BRS SC1', and SCS 437', respectively, when irrigated with water of 3.5 dS m-1. The genotype 'BRS Sol do Cerrado' showed an increase in the synthesis of photosynthetic pigments when irrigated with water of 3.5 dS m-1, with maximum values estimated at 1439.23 μg mL-1 (Chl a); 290.96 μg mL-1 (Chl b); 1730.19 μg mL-1 (Chl t); and 365.84 μg mL-1 (carotenoids). An increase in photosynthetic efficiency parameters (F0, Fm, and Fv) of the genotype 'BRS Gigante Amarelo' was observed when cultivated with water with high electrical conductivity (3.5 dS m-1).

How is the water footprint of the species Vachellia farnesiana, Amburana cearensis, and Handroanthus impetiginosus influenced by abiotic stresses as water deficit and salinity?

In semi-arid regions, is necessary to explore strategies to mitigate abiotic stresses such as water deficit and salinity. This study aimed to evaluate the stress tolerance capacity of three species subjected to different water regimes and salinity levels, based on dry matter production and water use efficiency (WUE). The species Handroanthus impetiginosus, Vachellia farnesiana, and Amburana cearensis were evaluated in combination with different water regimes (50%, 75%, and 100% of reference evapotranspiration - ET0) and salinity levels (0.18, 1.50, and 1.90 dS m-1). The results show that biomass accumulation increased at 50% and 75% ET0, while the WUE decreased at 100% ET0. The salinity level (1.90 dS m-1) caused reductions in leaf dry biomass (LDB), total dry biomass (TDB), LDB/TDB ratio, and WUE. The negative effects of high salinity on plant height were greater with the application of 75% ET0. The highest WUE was obtained at 50% ET0 for A. cearensis and H. impetiginosus, while V. farnesiana obtained the highest WUE at 75% ET0. A. cearensis exhibited the highest biomass accumulation (2.58 g) and WUE (0.21 g L-1). Overall, the species can tolerate drought and salinity conditions, being sensitive to high salinity concentrations during their initial growth.

Comparative genetic, biochemical and physiological analysis of sodium and chlorine in wheat

Plant with a great diversity shows several responses towards the biotic and abiotic stresses. Among these abiotic stresses, salinity is the main damaging factor as it reduces the yield of wheat plant with moderate salt tolerance. For its survival, plant undergoes through some genetic, biochemical and physiological changes to tackle the stress. This review mainly describes the conditions where various ions present in the soil, especially sodium and chlorine, enter into the plant and the genes or proteins involved with survival mechanism against the damage in plants. Salt stress causes alteration in enzymatic activity and Photosynthesis, oxidative stress, damage of cellular structure and components and ionic imbalance. Ion toxicity stress occur due to accumulation of excessive sodium ion and chloride ion. Transcriptional factors TaPIMP, TaSRG and TaMYBsdu 1 play key role in gene expression mechanism to overcome the stress. High affinity potassium transporter gene family is responsible for salt tolerance in wheat plant. HKT1;4 and HKT1;5 genes are responsible for Na exclusion in Triticum monococcum. Forty QTLs were found with the marker assisted selection in bread wheat for salinity tolerance and some morphological traits, 5 QTLs were related to sodium ion exclusion. In bread wheat, salt stress tolerance mechanism is mainly an exclusion of Na⁺ ions but also include K⁺ ion concentration. The salinity tolerant germplasm MW#293 provides an opportunity for the development of future salinity tolerant bread wheat.

Fullerenol regulates oxidative stress and tissue ionic homeostasis in spring wheat to improve net-primary productivity under salt-stress

The effects of fullerenol nanopriming (0, 10, 40, 80 and 120 nM concentration) on salt stressed-wheat (0 and 150 mM NaCl) were investigated under natural conditions. Salinity resulted in a shift in wheat growth pattern in the form of LAR (+ 40.9% increase) and RGR (+ 13.4% increase) while decreased NAR (- 31.7%). It also disturbed shoot and root biomass, ion uptake and reduced chlorophyll contents. Despite increase in enzyme activities, higher ROS generation (+ 48.1% O₂^- anion; and + 62.2% H₂O₂) and lipid peroxidation (+ 40.8% MDA) were detected in salt-stressed wheat plants. Possibly, the increases in enzyme activities were not up to the level to completely counteract the salinity induced oxidative stress. Nanopriming with fullerenol improved NAR (+ 8.77% to 23.2%), ROS metabolism and decreased indicators of oxidative stress. Hydropriming treatment also promoted NAR recovery by 21.9% than control plants. Compared to Na⁺ ions, improvements in shoot relative concentrations of K⁺, Ca²⁺ and P also recorded along with soluble sugars and amino acids, which improved osmotic balance. These biochemical modifications contributed to improvements in grain yield attributes (+11.8% to 18.3% in 100 grain-weight) than salinity stressed control. Hydropriming also contributed to a recovery in grain yield attributes by 12.6%. Above all, the harvested seeds from fullerenol treated plants also showed better germination and seedlings growth traits. Conclusively, we report non-toxic, growth-promoting effects of fullerenol nanoparticles on wheat crop and as a way forward; we suggest its exogenous application to recover crop productivity under saline environments.

Responses of antioxidative enzymes and gene expression in Oryza sativa L and Cucumis sativus L seedlings to microcystins stress

Microcystins (MCs) have become an important global environmental issue, causing oxidative stress, which is an important toxic mechanism for MCs in plants. However, the regulating mechanism of antioxidative enzymes in plants in adapting to MCs stress remains unclear. We studied the dynamic effects of MCs at different concentrations (5, 10, 50 and 100 μg/L) in rice and cucumber seedlings on relative growth rate (RGR), and reactive oxygen species and malondialdehyde (MDA) content, and antioxidative enzyme activities, during a stress period (MCs exposed for 1, 3, 5 and 7 d) and recovery period (7 d). During the stress period, MCs at 5 μg/L inhibited RGR in cucumber and promoted RGR in rice. The contents of superoxide anion (O₂·^-), hydrogen peroxide (H₂O₂) and MDA increased and RGR declined in both crops with time and intensity of MCs stress. For cucumber, all these parameters responded earlier to MCs stress, and O₂·^-, MDA and RGR were more responsive to MCs stress than in rice. Moreover, catalase (CAT) and peroxidase (POD), and the relative expressions of CAT genes increased in both crops at 5-100 μg/L MCs, whereas relative expression of POD genes increased only in cucumber. Diversely, superoxide dismutase (SOD) response to MCs in cucumber leaves was later than for rice. MCs at 100 μg/L decreased the relative expression of SOD genes in cucumber but did not change SOD activity. During the recovery period, all the above indicators in both crops were higher than the control and lower than in the stress period. Conversely, RGR was lower than in the control and higher than in the stress period, except for cucumber which was lower, and MDA content higher than the stress period at 100 μg/L MCs. Overall, these results indicated that cucumber was more sensitive to MCs than rice, and SOD, CAT and POD play an important role in plant response to MCs stress.