| In this thesis, pot experiments, physico-chemical property test andsimulated leaching trails were conducted to determine the effects and mechanisms ofsuper absorbent polymers on 1) water saving, 2) promoting plant growth, 3) Nitrate-N,ammonium-N, amide-N and water retention in super absorbent polymer-amended soillessplant growth medium and 4) drought-resistance of cucumber seedlings. In addition,formulations of soilless media and factors of diminished super absorbent polymersabsorption property were studied. The results were as follows:Treatments including T5, T7, T10. T11, T13 and T14 were superior to vegetable soil andother treatments and could further study or spread application.? The absorption capabilities of super absorbent polymers were not significantlyinfluenced by varied pH values between pH 6~8.The differences absorption capabilities of super absorbent polymers were significant in distilled water, tap water and two soil solution. All polymers absorbed more distilled water than others treatments.All polymers absorption capabilities decreased with the sodium chloride solution concentration increased, especially when the concentrations of sodium chloride solution were lower than 0.020M.At same equivalent concentration, polymers absorptions of solutions comprising monovalent cations (i.e. NH4+, Na+, K+) were generally greater than for divalent species (e.g. Mg2+, Ca2+).(D Accumulated water loss of the treated growth medium decreased and the days to wilting point of plant delayed with polymers rates increased. At early period, high application rates suppressed, but as time went on, promoted plants growth. The effects of super absorbent polymers on dry weiht and water use efficiency of plant varied with different SAPs and mass percent in a soilless medium. There were extremely positive correlations between water use efficiencies of plant and mass percent of SAPs in a soilless medium. The effects of Mulpine super absorbent polymers KL and B were superior to 98 Kehan super absorbent polymer KH1 and Starch poly acrylonitrile graft co-polymers D under exhausted condition.Under equal service water, Mulpine super absorbent polymers B and KL polymers promoted plants growth, while KHi and KH2 inhibited plants growth.In decreaser service water experiment, Mulpine super absorbent polymers KL - Band 98 Kehan super absorbent polymer KH1 promoted plants growth, but the effect of 98 Kehan super absorbent polymer KH2 on plants growth was not significant.In conclusion, the application effect of super absorbent polymer B was the best one of the five polymers under three water conditions.Water retention by the growth medium increased with polymer rates increased linearly. 4.03-8.34% of applied amide-N was recovered in the resulting leached of the polymer-amended media, while 34.17~52.55% of the nitrate-N was recoverd, and only 3.85~6.26%of the ammonium-N was recovered. In urea treatment, super absorbent polymer not only promoted cucumber seedlings fresh weight and dry weight by 5.3-32% and 5.5~25.5% respectively, but also had clear advantages in promoting N content and total N in cucumber seedlings. Super absorbent polymers increased urea utilization percent by 6~22%. But in ammonium nitrate treatments, plant dry weight and N content in plant were not significantly increased and total N in plant was increased only at the highest polymer rate. Ammonium nitrate-N utilization percent only increased by 0.66-2.53%.Under water stress, Mulpine super absorbent polymer B promoted plant growth through regulating a series of physiology activity of cucumber seedlings, such as improved root activity by 6.26-83.53%, thus leaf water content increased and stress susceptibility index and proline content in leaf decreased evidently.
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