Growth parameters, the content of proline and flavonoids. Na+ and K+ion accumulation in the shoots of four species of halophytes from the family Chenopodiaceae inhabiting the territory of the South...

With continued population growth, increasing staple crop production is necessary. However, in dryland areas, this is negatively affected by various abiotic stresses, such as drought and salinity. The field screening of 10 improved genetic lines of pear millet originating from African dryland areas was conducted based on a set of agrobiological traits (i.e., germination rate, plant density, plant maturity rate, forage, and grain yields) in order to understand plant growth and its yield potential responses under saline environments. Our findings demonstrated that genotype had a significant impact on the accumulation of green biomass (64.4% based on two-way ANOVA), while salinity caused reduction in grain yield value. HHVBC Tall and IP 19586 were selected as the best-performing and high-yielding genotypes. HHVBC Tall is a dual purpose (i.e., forage and grain) line which produced high grain yields on marginal lands, with soil salinization up to electrical conductivity (EC) 6–8 dS m⁻¹ (approximately 60–80 mM NaCl). Meanwhile, IP 19586, grown under similar conditions, showed a rapid accumulation of green biomass with a significant decrease in grain yield. Both lines were tolerant to drought and sensitive to high salinity (above 200 mM NaCl). The threshold salinity of HHVBC Tall calculated at the seedling stage was lower than that of IP 19586. Seedling viability of these lines was affected by oxidative stress and membrane peroxidation, and they had decreased chlorophyll and carotenoid biosynthesis. This study demonstrated that ionic stress is more detrimental for the accumulation of green and dry biomass, in combination with increasing the proline and malonic dialdehyde (MDA) contents of both best-performing pearl millet lines, as compared with osmotic stress.

Chenopodium quinoa is a genetically diverse crop that can adapt to a wide range of environments, including temperatures and salinities. However, only a few studies have assessed the combined effects of two or more environmental factors on C. quinoa. Here, we investigated the effects of salinity (300 mM NaCl), elevated temperature (35 °C), and their interaction with growth, water–salt balance, the efficiency of photosystem II (PSII), the activity of cyclic electron transport (CET) around photosystem I (PSI), Rubisco and PEPC enzyme content, and the expression of photosynthetic genes. We found that elevated temperature did not decrease the biomass but caused a significant increase in the water and potassium content of C. quinoa leaves. The decrease in PSII efficiency under elevated temperature was accompanied by an increase in the expression of genes encoding the components of PSII (psbA) and linear electron transport (FDI), as well as the main photosynthetic protein Rubisco (rbcL). Moreover, the strongest effect was induced by the combined effect of elevated temperature and salinity, which induced high oxidative stress (a threefold increase in MDA), a threefold decrease in the biomass, a twofold decrease in PSII efficiency, and a two- to eightfold decrease in the expression of the photosynthetic genes psbA, FDI, and rbcL. PSI was more tolerant to all forms of stress; however, the combined effect of elevated temperature and salinity downregulated the expression of PGR5 and FNR1, which may diminish the role of PGR5/PGRL1-dependent CET in favor of the NDH-dependent CET of PSI. The obtained data on the functioning of photosystems and the expression of photosynthetic genes under combined stress (elevated temperature and salinity) can make a significant contribution to understanding the mechanisms of tolerance of C. quinoa to multiple stresses under climate change conditions.

The review discusses up-to-date concepts of interrelations between photosynthesis and respiration. It considers the quantitative ratio of the processes in the leaf and that in the whole plant...

The thermal stability of plants with different types of photosynthesis Chenopodium quinoa Willd. (C₃) and Amaranthus retroflexus L. (C₄-NAD) to short-term elevated temperature (35°С, eT) at ambient (400 ppm, aCO₂) and elevated (800 ppm, eCO₂) CO₂ concentration was investigated. Growth parameters, water, proline, and MDA content, CO₂/H₂О gas exchange parameters, the functioning of PS I and PS II, and the content of key photosynthetic (Rubisco, PEPC) and photorespiratory (GDC) enzymes were analyzed. Under control conditions, C₄-type plants, compared with the C₃-type, show higher values of dry biomass growth, intensity of visible photosynthesis, transpiration, and PS I activity and lower proline content. The photosynthetic and stomatal apparatus of both types was sensitive to eT, which manifested itself in a decrease in the intensity of apparent photosynthesis and transpiration. In addition, suppression of light reactions (PS II) and intensity of photorespiration (according to GDC) was observed in the C₃-species and an increase in the content of proline in the C₄-species. Under eCO₂ conditions, the C₃-species showed a decrease in the intensity of photorespiration, while oxidative stress (twofold increase in the content of MDA) was accompanied by reduced intensity of apparent photosynthesis, transpiration, and increased intensity of dark mitochondrial respiration in the C₄-species. A softening effect of eCO₂ on thermal stability data for C₃- and C₄-plants was not established. With the combined action of eCO₂ and eT, both types exhibited oxidative stress, reduced efficiency of PS II and apparent photosynthesis, and activation of dark respiration. However, differences were also observed: oxidative stress was accompanied by a decrease in the increase in dry biomass and water content in tissues, as well as suppression of photorespiration, in the C₃-species, while there was a decrease in the intensity of transpiration and an increase in the content of PEPC in the C₄-species. Reduced WUE with combined action of eCO₂ and eT in plants of the C₄-species was less significant than the C₃-species. The different response of quinoa plants (C₃) and amaranth (C₄) on the combined effect of climatic factors of elevated temperature and CO₂ concentration is discussed.

We studied the effects of wheat (Triticum aestivum L.) seed presowing treatment with 0.05 mM salicylic acid (SA) on its endogenous content and the ratio of free to bound forms in seedling shoots and roots. During two-week-long seedling growth, we observed a gradual decrease in the total SA content in shoots but not in roots. In shoots, the content of conjugated SA increased and that of its free form reduced. Seed presowing treatment with SA reduced total content of endogenous SA in both seedling shoots and roots. The content of free SA reduced intensely in shoots and somewhat less in roots. Such reduction was supposed to occur due to the disturbance in SA biosynthesis. These were accompanied by the increases in the shoot and especially root biomass and length, stimulation of total dark respiration, and changes in the ratio between respiratory pathways. In the roots, we observed an increased proportion of cytochrome respiration, whereas in the shoots — alternative cyan-resistant respiration. We also observed changes in the plant antioxidant system. A degree of lipid peroxidation was stronger in shoots than in roots. Pretreatment with SA resulted in MDA 2.5-fold accumulation in shoots, whereas its content in roots reduced by 1.7 times. We concluded that the type and intensity of SA effects on plant growth, energetic balance, and antioxidant status were related to changes in its endogenous content and redistribution between free and conjugated forms.