The Alleviation Effect of Silicon on Seed Germination and Seedling Growth of Tomato Under Salinity Stress
This study was conducted to evaluate the effectiveness of silicon (Si) application under salinity levels on seed germination and growth characteristics of tomato seeds. A laboratory experiment was performed on completely randomized design with two levels of salinity (25 and 50 mM NaCl) and 2 concentration of Si (1 and 2 mM) with 4 replications. Germination percentage, germination rate, seedling shoot and root length, fresh and dry weight of seedling and mean germination time was measured. Seed germination of Lycopersicon esculentum L. was significantly affected by salinity levels, Si and their interaction. Germination characteristics of tomato seeds decreased drastically by increasing NaCl concentrations. However, 1 mM Si had positive effects on seed germination characteristics and improved germination percentage, germination rate and mean germination time. Si alleviated the harmful effect of salinity stress on tomato seed germination at almost all germination characteristics.
Humic Acid Decreased Hazardous of Cadmium Toxicity on Lettuce (Lactuca sativa L.)
The binding of Cd to humic acid was studied. The influence of a Cd-humic complex on enzyme activities (superoxide dismutases, peroxidases), availability of Cd, and biomass compared with the behavior of no treatment (control). It was examined through a hydroponics system in lettuce. Treatments were: control (no additions), humic acid (0, 100 and 1000 mg·L-1), and Cd (0, 2 and 4 mg·L-1). Enzyme activities increased significantly with increasing rates of cadmium. A significant increase (P<0.05) in cadmium content of leaves result in a considerable decrease in the biomass (P<0.05). It can be concluded that the humic acid applied in the media led to a decrease the metal adsorption by plant. This material can be used to reduce the availability and mobility of heavy metals in the soils, too.