Studies On Cultivation Techniques Of Seedlings In Three Types Of Desert Plants

Haloxylon ammodendron,Nitraria tangutorum and Reaumuria soongorica are all very important resource species in the desert regions of our country.However,they have begun to gradually degenerate due to human activity and deteriorating natural environment in native regions.Recently,it have been identified that sodium plays an important role in the drought stress resistance of desert species.Our further experiments under sand culture in laboratory also proved that suitable sodium can not only stimulated the growth but also improved the osmotic stress resistance of the desert plant Zygophyllum xanthonylon.Subsequently,a sodium compound fertilizer was developed after a series of experiments.This fertilizer significantly promoted the growth and enhanced the drought stress resistance of Z.xanthonylon.Based on above works,in the present study,the roles of sodium compound fertilizer in the growth and drought resistance of the desert species H.ammodendron, N.tangutorum and R.soongorica were investigated under pots;meanwhile,the comparative studies of three kinds of sodium compound fertilizers were also carried out;based on these works,the application scope of sodium compound fertilizer was further expanded.The results showed that,after these three plants were exposed to drought stress for 20-22 days following normally watered for 11-12 weeks,the addition of sodium compound fertilizer 1,2 and 3 all promoted their growth and enhanced their drought stress resistance,but the sodium compound fertilizer 1 is the best one:H.ammodendron:under drought stress,compared with the treatment without fertilizer,the application of sodium compound fertilizer 1 significantly increased its plant height,photosynthesizing branch area,fresh weight,dry weight,water content and organic weight by 38%,79%,148%,100%,25%and 8.7%respectively; increased root fresh weight and dry weight by 63%and 45%respectively;meanwhile, the presence of sodium compound fertilizer 1 significantly increased the catalase (CAT),peroxidase(POD) and superoxide dismutase(SOD) activity by 32%,58%and 87%respectively;decreased the malondialdehyde(MDA) content and relative membrane permeability by 33%and 34%respectively;increased the phosphoenolpyruvate carboxylase activity,net photosynthetic rate(Pn) and water use efficiency(WUE) by 301%,200%and 445%respectively in its photosynthesizing branches. N.tangutorum:under drought stress,compared with the treatment without fertilizer, the application of sodium compound fertilizer 1 significantly increased its plant height, leaf area,fresh weight,dry weight,water content and organic weight by 89%,209%, 318%,218%,34%and 6.8%respectively;increased root fresh weight,dry weight and water content by 217%,138%and 43%respectively;meanwhile,the presence of sodium compound fertilizer 1 significantly increased the CAT,POD and SOD activity by 23%,30%and 25%respectively;decreased the MDA content and relative membrane permeability by 30%and 37%respectively;enhenced the stability of photosynthetic systemâ…¡,increased Pn and WUE by 420%and 915%respectively in its leaves.R.soongorica:under drought stress,compared with the treatment without fertilizer, the application of sodium compound fertilizer 1 significantly increased its plant height, leaf area,fresh weight,dry weight and water content by 321%,763%,800%,667% and 34%respectively;increased root fresh weight and dry weight by 719%and 628% respectively;meanwhile,the presence of sodium compound fertilizer 1 increased Pn and WUE by 38%and 159%respectively in its leaves.Under drought stress,the application of sodium compound fertilizer 1 increased the osmotic adjustment capacity,photosynthetic capacity and WUE of these three species and enhanced reactive oxygen species-scavenging capacity in H.ammodendron and N. tangutorum,which effectively enhances the drought resistance of these three species.In the process of sodium compound fertilizer experiments,we found that the N. tangutorum seeds present the extremely high dormancy rate.However,so far,there are only a few reports about the method of promoting seed germination of N. tangutorum.Threrefore,the studies on the method of promoting the N.tangutorum seed germination was also carried out in this paper,and then a rapid germination technical system of N.tangutorum seeds was established,the results as following:the seeds of N.tangutorum weren't germinated when dipped in distilled water under normal temperature(20-25℃).However,after seeds were soaked in 98%H₂SO₄ for 55 min and then dipped in 150mg/L GA₃ for 48 h,the germination reached a peak as 69%under the fluctuating temperature of 25/5℃(12h/12h) within 10 days,and seeds germinated more trimly than control.However,31%of seeds still remain dormancy, suggesting that N.tangutorum seeds have multiple dormancy mechanisms. Meanwhile,it was identified that the mechanical restriction of seed coat is the main reasons of N.tangutorum seed dormancy. The sodium compound fertilizer and N.tangutorum seed rapid germination technical system can be used to cultivate the strong drought-resistance seedlings of desert plants.Therefore,they have broad prospects in practice.