Studies Of The Effects And Mechanism Of Salt And Fertilizer On Helianthus Tuberosus L. With Seawater Treatments

Growing plants that are tolerant to seawater is one of options for exploitation of mudflats along the coast. The studies were included pot experiments in the greenhouse and field experiments in Laizhou sea-beach, Shandong Province. Pot experiments using hydroponic culture were carried out to study the effects of seawater and fertilizer on growth, osmotica accumulation, antioxidant enzyme, electrolytic leakage, photosynthetic characteristics and ion distributions of Helianthus tuberosus seedlings. The field experiments were carried out to study the coupling effects of salt and fertilizer application on Helianthus tuberosus irrigated with 0%, 25%, 50% and 75% seawater in 2003 and 2004. The results were showed as below:Pot experiments in the greenhouse:(1) Compared with the control, there were slight changes of FW (fresh weight) and D W (dry weight) of roots and aerial parts of Helianthus tuberosus seedlings treated with 10% and 25% seawater, whereas a significant decrease in both FW and DW occurred after 50% seawater treatment. But the contents of water in aerial parts and roots were the lowest under 50% seawater stress.(2) The activities of SOD (superoxide dismutase), POD (peroxidase) and CAT (catalase) in leaves of seawater-stressed plants were stimulated significantly compared to controlled plants, and the activities increased with seawater concentrations increasing and time lasting. The MDA (malondialdehyde) contents in leaves with 10% seawater were even lower than control, and they with 50% seawater treatment were highest in the term of experiments. Compared with the control, there were slight changes of ELP (electrolytic leakage percentage) in leaves of Helianthus tuberosus seedlings treated with 10% and 25% seawater, whereas ELP increased significantly with the treatment of 50% seawater. With time lasting, the ELP increased more under the stress of 50% seawater.(3) The contents of proline and soluble sugar increased with the seawater concentrations increasing. The contents of proline increased on Day 8 and decreased on Day 12 with the treatments of 10% and 25% seawater. But they increased significantly on Day 8 and onward under 50% seawater stress. The contents of soluble-sugar on Day 8 increased compared to those on Day 4 and decreased on Day 12 withthe treatments of 10%, 25% and 50% seawater. The contents of Na+ and Cl- in the aerial parts increased with the enhancement of seawater concentration. Compared with Na+, the K+ contents were the highest under 25% seawater stress. And the tendencies of Na+, Cl- and K+ in roots were similar with them in the aerial parts.(4) Under the same concentration of seawater, the fresh weight of roots and aerial parts increased with the concentration of nitrogen and phosphorus increasing. The trends of dry weight of roots and aerial parts resembled the trends of fresh weight with the same treatments. Compared with the control, the photosynthetic rates, transpiration rates, water use efficiencies, stomatal conductances and stomatal limitations treated with 10% seawater changed slightly, while they all decreased with the increase of seawater concentration under the concentration of N1 (7.5 mmol L-1) and P1 (1 mmol L-1). The photosynthetic rates, transpiration rates, stomatal conductances and stomatal limitations all increased with the increase of the concentration of nitrogen and phosphorus under the same seawater concentration. The catabatic effects were more significative when the seawater concentration increased. The water use efficiencies decreased with the treatments of control and 10% seawater, while they increased with the treatments of 25% and 50% seawater with the concentration of nitrogen and phosphorus increasing. Compared with the control, the internal CO2 concentrations treated with 10% seawater under the concentration of N1 (7.5 mmol L-1) and P1 (1 mmol L-1) changed slightly. And they increased with seawater concentration increasing. With the concentration of nitrogen and phosphorus increasing, they decreased with the treatments of the same seawater concentration.(5)...