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Low temperature is a major environmental factor that negatively affects the growth and productivity of plants, such as the tropical fruit Cape gooseberry (Physalis peruviana L.), which is susceptible to cold stress. Therefore, to investigate the effect of the amino acid L-phenylalanine (Phe), L-cysteine (Cys), or sodium selenite (Se) on enhancing antioxidant activities, experiments were conducted on the phenolic compounds, proline content, and membrane stability of Cape gooseberry seedlings under low-temperature stress. The seedlings were exposed for 48 h to a low temperature (4 °C) followed by 24 h of optimal growth conditions. In seedlings treated with Se, we found a high relative water content, good membrane integrity, low ion leakage, and hydrogen peroxide. Additionally, this treatment led to the improvement of photosynthetic pigments and antioxidant activity. The analysis of seedlings under cold stress showed that the Phe enhanced the stomatal conductance and phenol content. Furthermore, low concentrations of Cys resulted in the production of proline and flavonoids, which reduced the negative effects of environmental stress on seedlings and maintained cell membrane integrity. Overall, in this experiment, the use of Se and low concentrations of Cys had a positive effect on the amount of antioxidant compounds, which improved seedling growth under stress conditions. [ABSTRACT FROM AUTHOR]

Lettuce (Lactuca sativa L.) is salt-sensitive, and salinity level can negatively affect yield. The study was conducted to investigate effect of water enriched with seaweed extract to overcome effects of salinity in 'New Red Fire' leafy lettuce cultivation. The highest and lowest leaf free proline content was in plants irrigated with saline water at EC 7 and 1.37 dS m−1. Increasing water EC level from 2.5 to 4 dS m−1 resulted in 9.3% increase in leaf total soluble solid content. The highest leaf vitamin C content was in plants treated by Chlorella vulgaris seaweed solution. Salinity levels could be classified into three groups: 1.37 and 2.5 dS m−1 (least damaging), 4 and 5 dS m−1 (tolerance threshold) and 7 dS m−1 (most damaging). Chlorella vulgaris seaweed solution appeared to neutralize adverse effects of salinity on plant fresh weight, free proline content, total soluble solid content, photosynthetic pigments content, radical scavenging activity, anthocyanin content, phenol and flavonoid content, peroxidase enzyme activity and leaf vitamin C content. Irrigation 'New Red Fire' with water enriched with Chlorella vulgaris seaweed extract is strongly recommended to overcome effects of salinity on lettuce morphological and physiological characteristics. Salinity levels higher than 5 dS m−1 can seriously damage 'New Red Fire' qualitative and quantitative properties. [ABSTRACT FROM AUTHOR]

In this study, the effects of four concentrations of humic acid (0, 0.5, 1, and 1.5 kg ha−1, HA applied to the soil) and kinetin (0, 25, 50, and 75 mg L−1, KT, foliar sprayed) on vegetative growth, yield and biochemical attributes of radish cv. Watermelon, grown in two seasons of spring and autumn, were investigated. Results showed that, the number of leaves per plant, leaf area and chlorophyll content increased with application of HA and KT in both seasons, while the high levels of treatments had no significant effect on leaf number per plant and chlorophyll content in spring season. The root diameter, fresh weight and yield increased significantly with application of HA and KT in both seasons, though, this increase was noticeable in the autumn season. Our results also showed that radish root treated by HA and KT exhibited higher root firmness, vitamin C, anthocyanin content and total soluble solids (TSS), especially in autumn cultivation. Macronutrient contents of root including magnesium (Mg), phosphorus (P), potassium (K), nitrogen (N), and calcium (Ca) were significantly enhanced by HA and KT, however high concentration of KT in combination with high concentration of HA decreased some nutrient contents. Generally, the results of this study demonstrated that cultivation season is one of the most important management tools to minimize the negative effects of high temperature during root development. In addition, the benefits of KT spray combined with HA were inconsistent between both seasons, but showed more in the autumn crops. [ABSTRACT FROM AUTHOR]

In this experiment, the exogenous application of hydrogen sulfide (H2S; 1, 2 or 3 mM) and phenylalanine (PA; 2.5, 5, or 7.5 mM) to alleviate chilling injury and enhancing antioxidant activity and membrane stability of eggplant fruits (Solanum melongena cv. Hadrian) during storage at 7℃ for 21 days was investigated. Results indicated that H2S and PA alleviated chilling injury and reduced electrolyte leakage percentage and malondialdehyde accumulation. Exogenous application of H2S and PA maintained significantly higher levels of proline, total phenols, and flavonoids. It was also found that H2S and PA reduced the hydrogen peroxide accumulation with up-regulated activities of superoxide dismutase, catalase, and ascorbate peroxidase. These results indicated that H2S and PA alleviated chilling injury of eggplant fruit may through the enhancement of reactive oxygen species scavenging system activity, proline, and phenolic accumulation. [ABSTRACT FROM AUTHOR]