Researches On Recovery The Seawater-intrusion Fields&Plant Characteristics Under Seawater Stress Of Mesembryanthemum Crystallinum L.

Saline soil in Hainan is an important regenerative reserve land resources,and the main source of salinization of land in Hainan Province is seawater,which requires special treatment and protection programs.The planting of seawater-tolerant vegetables not only makes good use of the seawater intrusion fields,but also plays a role of fixing the soil on the coastal beach and provides a new type of "natural pollution-free" vegetables.Therefore,it is very important ecological and economic significance to breed suitable varieties of the seawater-tolerant vegetables and to study their resistance to seawater stressed physiology,for the improvement of saline soil and agricultural development in Hainan Province.In this paper,Mesembryanthemum crystallinum L.was used as experimental material to study the soil desalination rate,Na+ and Cl-accumulation through inoculation of a small area in the seawater intrusion field.The nutrient contents of the M.crystallinum L.were also preliminarily analyzed.Six concentrations of seawater treatments were set up,the changes of morphological structure,physiology and biochemistry and taste and flavor of M.crystallinum under seawater stress were studied and discussed.The main findings are as follows:1.The growth of M.crystallinum was vigorous with high biomass in the seawater intrusion fields,and the accumulation of Na+ and Cl-in vivo of plant reaches up to 6.59%and 7.23%,respectively.It has strong salt absorption ability and the average desalination rate reaches up to 70%;and could take about 200 kg NaCl/per mu area off.2.Each 100 g of M.crystallinum contains carbohydrates 2.8 g,crude fat 0.2 g,total flavonoids 4.6 g,vitamin C1.3 mg,vitamin E13 mg,?-carotene 1.04 mg and EAA748 mg,which is a low sugar,low fat contents,and high total flavonoids,vitamin and EAA rich vegetable.3.M.crystallinum can complete the life cycle under the stress of 100%seawater,which showed strong tolerance to seawater,and grew vigorously under the treatment of 20%seawater concentration.The edible parts of M.crystallinum under the stresses of the different seawater concentrations were not much difference in color,shape,and smell;however the best in taste such as acidity,sweetness,bitterness and saltiness was under the stress of 20%and 40%seawater.4.With the increase of the stressed seawater concentration,the salt content in vivo of single plant and epidermal salt vesicles showed an increasing trend,which the highest Na+and Cl-contents were up to 31.059%and 35.527%of plant;under the treatment of 80%seawater,the salt vesicles in the leaf-epidermis were large and sparse.Under the treatment of 100%seawater,the epidermal salt vesicles were large and close arrangement with no spacing.5.Under seawater stress,the activities of antioxidant enzymes(SOD,POD,CAT)in vivo of M.crystallinum could be activated.Under the stressed seawater concentration was less than 60.00%,during the plant growth,the activity of SOD was increased;POD showed a first increasing,then decreasing,and followed an increasing;CAT activity was less than 1.00 U/g.Under the stressed seawater concentration was more than 60.00%,SOD and POD activities were decreased with the growth of M.rystallinum;however CAT activity showed an increasing trend with the growth,and it was rapidly increased when the stressed seawater was 100.00%.Antioxidant enzyme protection system with the strongest correlation with seawater stress was SOD,while the activation of CAT requires the content of H2O2 and O2-reaches a certain level in vivo of M.crystallinum.6.Under seawater stress,the content of proline and soluble sugar in vivo of M.crystallinum was increased.When the stressed concentration exceeded up to the optimum concentration for plant growth,the content was negatively correlated with the stressed seawater concentration,and positively correlated with the growth of plant,which mainly maintained the growth of M.crystallinum.In summary,the salt-absorbing ability of M.crystallinum is strong,it has a high desalination rate for soil,and its nutritional value is very high.It also shows physiological and biochemical responses to seawater stress on tissues and organs,reduces the toxicity of salt by storing and transferring Cl-,Na+ to epidermal salt vesicles,increasing the activity of antioxidant enzymes and the content of osmotic adjustment substances.It has a very broad development prospect for the improvement of saline soil.