Effect Of Different Salts On Growth, Physiological And Biochemical Characteristics Of Cucumber Seedlings

In the establishment cultivation such as greenhouse and shed of horticultural crops,because fertilizer was unreasonablely applied, culture management was unsuitable, and ground water rised, which caused soil secondly salinization. The main anion of facilities soil salt is NO3-, the main cation is Ca2+ and K+. Therefore, this experiment was desighed about the effect of different salt treatments on physiological and biochemical characteristics of cucumber seedlings.The main results were as follows:1. High cocentration nitrate inhibited the growth of cucumber seedlings. There were great differences in effect of different nitrates on cucumber seedlings. With the increasing of NO3- concentration, the biomass, root absorbability and root absorbing area declined under NaNO3 treatment. The biomass was gradually increased with NO3- concentration increasing under Ca(NO3)2 and KNO3 treatments, while NO3- concentration excessed 98 mmol·L-1, the fresh weight of cucumber seedlings was gradually decreased. Under the same NO3- concentration, the growth of cucumber seedlings under Ca(NO3)2 was better than under KNO3.2.Under nitrate stress, the MDA content, the relative electronic leakage and protective enzyme activity were gradually increased. There were different responses on cucumber seedlings under different nitrate treatments. While NO3- concentration was less than 98 mmol·L-1, there were no distinct changes in MDA content and electri conductivity by Ca(NO3)2. But the MDA content and the relative electronic leakage were increased under NaNO3 and KNO3. Compared with other nitrates, the protective enzyme activity ubder NaNO3 were higher .3.There were different responses on photosynthesis characteristic of cucumber seedlings under different nitrate treatments. The chlorophyll content, photosynthesis rate , transpiration rate and stomatal conductance rised gradually, increasing concentrations of NO3- from 14 to 98mmol·L-1, while increasing the concentration continuously, photosynthesis ability declined. There were no obvious changes on photosynthetic parameters under KNO3 treatment, photosynthetic parameters of cucumber seedlings leavese under NaNO3 descended gradually.Whlie NO3- concentration was more than 140and 98 mmol·L-1, the leaf was wilting. The decreasement of photosynthesis ability of cucumber seedlings leavese was caused by high concentration of NaNO3 and KNO3.4. There was great effect of different nitrate treatments on absorption of mineral elements. With the increase of NO3- concentration, the content of P, Fe and K increased under low Ca(NO3)2 concentration, then declined. The content of P and Ca increased with the increasing of NO3- from 14 to 98 mmol·L-1 , and reached the maximum while NO3- was 98 mmol·L-1 under KNO3 , then declined. However,the content of Fe gradually declined. Under NaNO3 treatment, P, K, Ca and Fe content in leaf and root were lower than control.5. Two kinds of sodium salts inhibited the growth of cucumber seedlings. Compared with under NaCl treatment, the biomass, root absorbability and photosynthesis rate were lower under NaNO3, but osmotic potential, osmoregulation substance content, MDA content, the relative electronic leakage and protective enzyme activity were higher than under NaNO3. Which was because the content of Na+ of cucumber seedlings under NaNO3 was remarkably higher than under NaCl, high Na+ concentration has the poison function on cucumber seedlings. The growth of cucumber seedlings under NaCl was better than under NaNO3, but worse than under Ca(NO3)2 and KNO3.