Seedling growth and photosynthetic response of Pterocarpus indicus L. to shading stress

Exogenous melatonin enhances heat tolerance in buckwheat seedlings by modulating physiological response mechanisms

Melatonin (MT) serves as a potent antioxidant in plant organisms, bolstering their resilience to temperature stress. In this study, the impact of MT on various buckwheat varieties under high-temperature stress conditions (40 °C) was investigated. Specifically, five buckwheat seedling varieties, comprising three sweet buckwheat variants (Fagopyrum esculentum) and two bitter buckwheat types (Fagopyrum tataricum), were subjected to foliar sprays of melatonin at concentrations of 50, 100 and 200 μM, with water at 25 °C employed as a control. Results demonstrated that exogenous MT at different concentrations improved the growth and physiological parameters of buckwheats, ameliorating damage induced by high-temperature stress. Notably, the application of 100 μM MT significantly augmented shoot biomasses of buckwheat seedlings under high-temperature conditions. Furthermore, the MT significantly increased the levels of osmotic adjustment substances and chlorophyll concentrations, enhanced antioxidant enzyme activities, chlorophyll fluorescence parameters, and improved photosynthetic gas exchange parameters in five different varieties of buckwheat. This led to the alleviation of damage to buckwheat seedlings subjected to high-temperature stress. Subsequently, five advanced statistical analysis methods: Principal Component Analysis, Grey Relational Analysis, Path Coefficient Analysis, Membership Function Method, and Coupling Coordination Analysis were employed to delve deeper into the existing data indicators. To summarize, the beneficial effect of exogenous melatonin on seedling growth is primarily achieved through the coordination and regulation of the antioxidant enzyme system and osmotic regulatory substances, ensuring the growth and development of buckwheat seedlings while also improving their heat tolerance. The treatment with a concentration of 100 μM of MT was the most effective.

Biostimulatory Effects of Chlorella fusca CHK0059 on Plant Growth and Fruit Quality of Strawberry

Green algae have been receiving widespread attention for their use as biofertilizers for agricultural production, but more studies are required to increase the efficiency of their use. This study aimed to investigate the effects of different levels of Chlorella fusca CHK0059 application on strawberry plant growth and fruit quality. A total of 800 strawberry seedlings were planted in a greenhouse and were grown for seven months under different Chlorella application rates: 0 (control), 0.1, 0.2, and 0.4% of the optimal cell density (OCD; 1.0 × 107 cells mL-1). The Chlorella application was conducted weekly via an irrigation system, and the characteristics of fruit samples were monitored monthly over a period of five months. The growth (e.g., phenotype, dry weight, and nutrition) and physiological (e.g., Fv/Fm and chlorophylls) parameters of strawberry plants appeared to be enhanced by Chlorella application over time, an enhancement which became greater as the application rate increased. Likewise, the hardness and P content of strawberry fruits had a similar trend. Meanwhile, 0.2% OCD treatment induced the highest values of soluble solid content (9.3-12 °Brix) and sucrose content (2.06-2.97 g 100 g-1) in the fruits as well as fruit flavor quality indices (e.g., sugars:acids ratio and sweetness index) during the monitoring, whilst control treatment represented the lowest values. In addition, the highest anthocyanin content in fruits was observed in 0.4% OCD treatment, which induced the lowest incidence of grey mold disease (Botrytis cinerea) on postharvest fruits for 45 days. Moreover, a high correlation between plants' nutrients and photosynthetic variables and fruits' sucrose and anthocyanin contents was identified through the results of principal component analysis. Overall, C. fusca CHK0059 application was found to promote the overall growth and performance of strawberry plants, contributing to the improvement of strawberry quality and yield, especially in 0.2% OCD treatment.