| My experiment can mostly include two sections: the first one was a pot experiment which was carried out in the greenhouse to study the physiological responses of Helianthus tuberosus L. seedlings to salt and water stress; the second one was a field experiment which was carried out in Laizhou, Shandong Province to study the effects of seawater irrigation on Helianthus tuberosus L. and soil. The results were as below:Under NaCl stress, the sum of inorganic ions had a significant increase and their contribution to the calculated osmotic potential (COP) was up to 95-97%. The great increase of Na+ and Cl- content accounted for 52-68% of COP, whereas the total content of organic solutes decreased slightly and their contribution to COP was about 3-5%. Under water stress, the content of inorganic ions were higher than that of CK, but lower than that of iso-osmotic NaCl treatment. Otherwise, the content of organic solutes were lower than that of both CK and iso-osmotic treatment under water stress. The results also showed that with the increasing of NaCl concentrations, both the electrolyte leakage and the content of MDA increased. And under water stress, both the electrolyte leakage and the content of MDA had no significant difference compared with those of CK, but were lower than those of iso-osmotic NaCl treatment. Furthermore, the content of Na+ and Cl- in the leaves was positively correlated with the electrolyte leakage and the content of MDA of leaves, and the correlation levels of the content of Na+ and Cl" and the electrolyte leakage are significant.Under NaCl and PEG stresses, the content of Na+, Cl- in root, stem and leaf increased but the content of K+ had no significant changes. The content of Na+ in stem is higher than that in root and leaf. With the concentration of NaCl increasing, the selective adsorption of K+ and Na+ (SK,Na) for root, stem and leaf gradually increased, and SK,Na for stem was lower than that for root and leaf. With the concentration of NaCl increasing, activities of SOD and POD in leaf increased at first then decreased As compared with under condition of control treatment and iso-osmotic NaCl stress, under PEG stress SOD activities in leaf increased 31.1% and 27.1%, but POD activities decreased 26.0% and 36.1% respectively.The stem of Helianthus tuberosus (L.) had the ability of containing high contents of Na+ and Cl-, and selectively absorbed K+ in high proportions seawater irrigation; The above and tubers yields of Helianthus tuberosus (L.) hadn't decreased until at the 50% proportions seawater irrigation where the yields decreased by 37% and 32% in contrast tofreshwater-irrigated. It meant that through natural weather, reduction of yields was occurred by salinity of irrigation water but the reduction was not significant until the proportions of seawater in irrigation water were the same as 50% or above it. The irrigation with seawater hadn't affected the inulin contents hi Helianthus tuberosus (L.) tubers, and the contents of inulin in Helianthus tuberosus (L.) were from about 40% to 65%.Salt contents hi root zone soil were greatly influenced by rainfall. Salt buildup did not exist on the condition of enough rainfall, on the contrary salt accumulated obviously on the condition of low rainfall in the root zone soil. But on the later condition the trend of accumulation turned to be stable in the W3 treatment (Vseawater/ V Pure water=1)- In root zone soil, variation of SAR value accorded with total salt accumulations and sometimes decreased at the treatment where the V seawater/ V pure water>1. Contents of Cl- and Na+ which were the main ions and leached obviously in 0-60cm soil were greatly influenced by rainfall, but the rainfall did not affected the contents of Ca2+, Mg2+ and K+ whose ability of leaching is worse than that of Cl- and Na+ in the root zone soil obviously. The vertical distribution of salt ions in the 0-60cm soil were mainly affected by the ratio of V seawater/ V pure water in the irrigation water on the condition of not enough rainfall, but on the cont... |
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