Silicon alleviates salinity stress in licorice (Glycyrrhiza uralensis) by regulating carbon and nitrogen metabolism

Salt stress is one of the key factors that limits the cultivation of Glycyrrhiza uralensis Fisch. (G. uralensis) in the northern part of China. In this study, three salt treatments (including 21, 42 and 63 ds/m NaCl/kg dry soil) and four Si (silicon) concentrations (including 0, 1.4, 2.8 and 4.2 ds/m SiO2/kg K2SiO3 in dry soil) were tested using G. uralensis as the plant material in a pot experiment with three replications. The results showed that the application of various concentrations of Si increased sucrose synthetase (SS), sucrose phosphate synthetase (SPS) and glutamine synthetase (GS), as well as nitrate reductase (NR) activities, and promoted carbon and nitrogen metabolism. Si application also increased the root dry weight of G. uralensis. Multilevel comparative analysis showed that the application of 2.8 ds/m SiO2 was the optimum rate for improved growth and yield of G. uralensis under different salt levels. This study provides important information that can form the basis for the cultivation of high-yielding and high-quality G. uralensis in saline soils.

Sugar Metabolism and Relative Enzyme Activities during Fruit Development and Ripening of Papaya

This study examined the relationship between the activity of fruit enzymes involved in metabolizing sucrose and sugar accumulation during fruit development, to clarify the role of these key enzymes in sugar accumulation in papaya fruit. Papaya fruit (Carica papaya L. cv. Sunset) were harvested from 14 to 140 days after anthesis (DAA). Fruit dry matter persent, total soluble solids (TSS), and sugar composition and the activity of enzymes: sucrose phosphate synthetase (SPS), sucrose synthetase (SS), and acid invertase were measured. `Sunset' papaya matured 140 days after anthesis during the Hawaii summer season and in about 180 days in cool season on the same plant. Fruit flesh dry matter persent, TSS, and total sugar did not significantly increase until 30 days before harvest. Sucrose synthetase was very high 2 weeks post-anthesis, then decreased to less than one-third in 42 to 56 DAA, then remained relatively low during the rest of fruit development. Seven to 14 days before fruit maturation, SS increased about 30% at the same time as sucrose accumulation in the fruit. Acid invertase activity was very low in the young fruit and increased more than 10-fold 42 to 14 days before maturation. SPS activity remained very low throughout the fruit development and was about 40% higher in mature-green fruit. The potential roles of invertase and sucrose synthetase in sugar accumulation will be discussed.

Effect of low temperature stress on the expression of sucrose synthetase in spring and winter wheat plants. Development of a monoclonal antibody against wheat germ sucrose synthetase

A monoclonal antibody against wheat germ sucrose synthetase is developed and characterized. Its use in studying the effect of cold acclimation on the expression of sucrose synthetase in winter and spring wheat plants is described. The antibody shows cross-reactivity with sucrose synthetase from maize and pea plants, as well as carrot cells. A gradual accumulation of the enzyme as a function of time spent at 2 °C is observed in both wheat varieties. In contrast, an initial sharp rise in the mRNA level is observed, which agrees with the previously reported response of maize plants subjected to anaerobic stress.Key words: cold tolerance, antibodies, protein expression, sucrose synthetase.