Strigolactone is a newly discovered type of plant hormone that has multiple roles in modulating plant responses to abiotic stress. Herein, we aimed to investigate the effects of exogenous GR24 (a synthetic analogue of strigolactone) on plant growth, photosynthetic characteristics, carbohydrate levels, endogenous strigolactone content and antioxidant metabolism in cucumber seedlings under low light stress. The results showed that the application of 10 μM GR24 can increase the photosynthetic efficiency and plant biomass of low light-stressed cucumber seedlings. GR24 increased the accumulation of carbohydrates and the synthesis of sucrose-related enzyme activities, enhanced antioxidant enzyme activities and antioxidant substance contents, and reduced the levels of H2O2 and MDA in cucumber seedlings under low light stress. These results indicate that exogenous GR24 might alleviate low light stress-induced growth inhibition by regulating the assimilation of carbon and antioxidants and endogenous strigolactone contents, thereby enhancing the tolerance of cucumber seedlings to low light stress.

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Lead (Pb) is a heavy metal pollutant and negatively affects agriculture and ecosystems. Pb can cause oxidative stress and abnormal plant growth. The ascorbic acid-glutathione (AsA-GSH) cycle mainly exists in chloroplasts and resists oxidative stress, scavenges reactive oxygen radicals, and maintains normal photosynthesis. However, the dosage related effects of Pb on pakchoi photosynthesis, via oxidative stress and the AsA-GSH system, remains unclear. In this study, various Pb dosage stress models were tested (low: 300 mg/kg; medium: 600 mg/kg; high: 900 mg/kg). Pb stress induced a dose-dependent increase in Pb content in pakchoi leaves (P < 0.05). Principal component analysis showed that Se, B, and Pb were significantly and negatively correlated. Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05). We also found that Vc content, as well as the GSH/GSSG ratio, decreased. Additionally, Pb stress destroyed chloroplast structure, decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD, and attenuated Fv/Fm and Fv/Fo (P < 0.05). In the high-dose group, the contents of chlorophyll a, chlorophyll b, and carotenoids decreased significantly, while the expression of chloroplast development genes (GLK, GLN2) decreased (P < 0.05). Our data suggest that Pb stress leads to dosage-dependent, aberrant photosynthesis by inhibiting the AsA-GSH system in pakchoi. This study expands the Pb toxicology research field and provides indications for screening antagonists.

In this study, we investigated the sex-specific ion uptake and physiological and biochemical responses to combined salinity and calcium treatments of male and female Populus deltoides under waterlogging conditions. Results indicate that both P. deltoides clones were sensitive to salinity and calcium. Under well-watered conditions, salinity stress could especially increase the Na content in female P. deltoides clones, whereas salinity and calcium could increase the K and Ca content in male clones. Waterlogging could evidently stimulate Na content in leaves under salinity, especially in female P. deltoides clones. However, waterlogging had no visible effects on the amount of Ca absorption between the two clones under abundant calcium conditions. The physiological and biochemical responses to combined salinity and calcium exceeded the effects of salinity or calcium individually. However, no significant difference was observed, hence indicating the similar responses of male and female P. deltoides clones. The lower Na content and Na:Ca ratio, and the higher K and Ca content in male clones suggest that the male clones could maintain ion homeostasis better than the female clones. The sexspecific differences in net photosynthetic rate, intercellular CO2 concentration, effective quantum yield of photosystem II, photochemical quenching coefficient, non-photochemical quenching coefficient, photosynthetic electron transport rate, content of superoxide anions, hydroxyl radicals, H2O2, soluble protein, and activities of superoxide dismutase under certain conditions suggest that female P. deltoides clones are more sensitive to salinity, calcium, and the combination of both than their male counterparts.

For large-scale industrial applications, it is highly desirable to create effective, economical electrocatalysts with longterm stability for the hydrogen evolution reaction (HER) at a large current density. Herein, we report a unique motif with crystalline CoFe-layered hydroxide (CoFe-LDH) nanosheets enclosed by amorphous ruthenium hydroxide (a-Ru(OH) 3 /CoFe-LDH) to realize the efficient hydrogen production at 1000 mA cm −2 , with a low overpotential of 178 mV in alkaline media. During the continuous HER process for 40 h at such a large current density, the potential remains almost constant with only slight fluctuations, indicating good long-term stability. The remarkable HER performance can be attributed to the charge redistribution caused by abundant oxygen vacancies in a-Ru(OH) 3 /CoFe-LDH. The increased electron density of states lowers the charge-transfer resistance and promotes the formation and release of H 2 molecules. The water-splitting electrolyzer with a-Ru(OH) 3 /CoFe-LDH as both an anode and a cathode in 1.0 M KOH demonstrates stable hydrogen production and a 100% faradic efficiency. The design strategy of interface engineering in this work will inspire the design of practical electrocatalysts for water splitting on an industrial scale.

In this study, ‘Xinli No. 3’, ‘Shengli rootstock’, ‘Shenli rootstock’ and ‘Shengzhen No. 1’ were used as rootstock, and ‘Jinchun No. 39’ cucumber was used as scion to study the effects of different rootstock on the yield and quality of grafted cucumber, and to select high quality rootstock suitable for cucumber grafting. Different rootstock affected the survival rate, phenology, the height of plant, stem diameter, growth potential, yield and quality of cucumber grafting. Among them, the survival rate of ‘Shenli rootstock’ grafted cucumber is the highest, and the growth of ‘Shengzhen No. 1’ grafted cucumber is relatively the strongest. There was no significant difference in fruit tuber, melon edge, thorn color and pulp crispness between self-rooted seedling (CK) and each rootstock grafting combination. The average yield of ‘Xinli No. 3’ grafted cucumber plot was not significantly different from that of self-rooted seedlings (CK). The length of ‘Shenli rootstock’ and ‘Shengli rootstock’ grafted cucumber was significantly higher than that of self-rooted seedlings (CK), and the length of ‘Shengzhen No. 1’ Grafted Cucumber was significantly higher than that of self-rooted seedlings (CK). The contents of vitamin C and soluble protein of ‘Shengli rootstock’, ‘Shenli rootstock’ and ‘Shengzhen No. 1’ grafted cucumber were significantly higher than those of self-rooted seedlings (CK), and the contents of soluble sugar were lower than those of self-rooted seedlings (CK). Therefore, ‘Shengzhen No. 1’ and ‘Jinchun No. 39’ have strong compatibility with cucumber. As rootstocks, the grafted cucumber plants not only have strong growth potential and high yield, but also significantly increase the content of soluble protein and vitamin C.

Lead (Pb) stress can cause oxidative stress and abnormal plant growth. The ascorbic acid-glutathione (AsA-GSH) cycle mainly exists in the chloroplast and is involved in resisting oxidative stress, scavenging reactive oxygen radicals in the chloroplast, and maintaining normal photosynthesis. However, whether Pb can affect the photosynthesis of pakchoi in a dose-dependent manner through the oxidative stress and AsA-GSH system is unclear. In this study, the low-dose (300 mg/kg), medium-dose (600 mg/kg) and high-dose (900 mg/kg) Pb stress models were established. In this experiment, methods such as ICP-MS, detection of photosynthetic characteristics and fluorescence characteristics, qRT-PCR, principal component analysis and correlation analysis were used. The results showed that Pb stress induced a dose-dependent increase in Pb content in pakchoi leaves. Principal component analysis discovered that Se, B and Pb were significantly negatively correlated. Pb stress caused an increase in MDA content and the decrease in SOD, GSH-Px and T-AOC activities. We also found that the Vc content and the GSH/GSSG ratio decreased. In addition, Pb stress resulted in the decreases of Pn, Tr, Gs, Ci, and VPD, and attenuated Fv/Fm and Fv/Fo. In the high-dose group, the contents of chlorophyll a, chlorophyll b and carotenoids were significantly decreased, and the expression of chloroplast development genes (GLK, GLN2) were abnormal. Taken together, our data suggests that Pb stress leads to aberrant photosynthesis in a dose-dependent manner by inhibiting the AsA-GSH system in pakchoi. The study expands the field of Pb toxicology research and provides indications for screening antagonists.