Study On Salt-alkaline Resistance And Removal Efficiency Of Nitrogen And Phosphorus By Several Hydroponic Plants In Coastal Estuary Heavy Saline-alkali Area

The convenient geographic location of coast area made many coastal cities become the hinge of the whole nations’economy, political, and transportation. Those cities contacted with the outside world closely and had developed economy which development rapidly. Owing to the habitat in the coastal area is often a saline and alkali exist at the same time, and as the high content of salt and alkali, aquatic plants in addition to response to salt stress, but also cope with high pH stress caused by alkali stress. Combined with a variety of open channel drainage tubes with the sewage discharged into coastal cities river system and led to serious water pollution, low plant survival rate with growth conditions bad. And large areas of desolated saline-alkali soil and depressed saline water seriously affect the region’s ecological landscape image and influence its rapid development. Therefore, the management of saline-alkali water becomes a problem to be solved first. The research of all kinds of aquatic plants which had good landscape effect, strong survival ability of salt alkali resistance was the problem most need to solve.The study of the mixed salt-alkali stress on plants’osmotic stress, ions poison indicated that the mixed salt-alkali stress could more explain the actual salt-alkali resistance of plants. This study is the bases of the integrated mechanism of salt-alkali tolerant plants which have important guiding significance to ecological restoration of water.This study use Phragmites australis and Typha orientalis, Lolium multiflorum, Miscanthus sacchariflorus, Iris pseudacorus, Althaea rosea as plant materials, NaCl and Na2CO3, NaHCO3 simulate different salinity (0～20‰) and pH (7.0～9.0) and product a mixture of salinity-alkalinity stress. Through treating seeds and seedlings with salinity-alkalinity stress respectively, determinations seed germination rate, seedling physiological indexes such as proline content to study the salt-alkali resistance of plants. Putting plants in water with salt (0～15‰), alkali (pH 7.0～9.0), and nitrogen, phosphorus, several days later then measuring the plant physiological indexes and nitrogen, phosphorus contents changes to study the water purification effect of plant. The results show that:1 Salt-alkali resistance of the seed of Lolium and Althaea rosea(1) The influence of alkali stress on seed germination was greater than salt stress. The influence of the united of salt stress and alkali stress were the greatest. There were almost no seed germination in high salt (20‰), pH 9.18.(2) The seeds of Lolium had stronger vitality under salt-alkali stress, and its germination rate, germination potential was higher than Althaea rosea. Namely, the seed of Lolium had better salt resistance than Althaea rosea.2 Salt-alkali resistance of the seedling of Phragmites australis, Typha angustifolia, Iris pseudacorus, Triarrherca sacchariflora, and Lolium(1) Phragmites australis could tolerat pH 8.13,15‰ salinity and pH 9.18,10‰ salinity; Triarrherca sacchariflora could tolerat pH 8.13,10‰ salinity and pH 9.18, 5‰ salinity; Typha angustifolia could tolerat pH 8.13,10‰ salinity and pH 9.18, 5‰ salinity; Iris pseudacorus could tolerat pH 7.64,10.5‰ salinity and pH 8.71, 3.5‰ salinity; Lolium could tolerat pH 8.13,10‰ salinity and pH 9.18,5‰ salinity.(2) The rank of salt-alkali resistance was Phragmites australis, Typha angustifolia, Triarrherca sacchariflora, Lolium, Iris pseudacorus.(3) This five kinds of plants could be the alternative plant to repair saline-alkali land and restore the local landscap3 The purification effect of Phragmites australis, Typha angustifolia, and Lolium(1) In the water had saline, alkaline, nitrogen and phosphorus, plant salt-alkali resistance was reduced.(2) Under salt-alkali stress, for ammonia nitrogen removal rate, australis had 2.7% higher than typha for average; For the removal effect on nitrate nitrogen Typha angustifolia had 2.5%、0.1% higher than Phragmites australis in slat and alkali stress, respectively; Under salt stress, the total nitrogen removal efficiency were similar of the two kinds of plants, and under alkali stress, Typha angustifolia had 8.2% higher removal efficiency than Phragmites australis; Under salt stress, Typha angustifolia had 7.3% higher removal rate of total phosphorus than Phragmites australis; However, under alkali stress, the removal rate of total phosphorus of Typha angustifolia was 1.4% lower than Phragmites australis.(3) Under alkali stress the processing efficiency of nitrogen and phosphorus of Lolium was better than salt stress.