外源硝态氮对菊芋耐海水胁迫的影响

A hydroponic experiment with six treatments, i.e., 0% seawater （control）, 10% seawater, 25% seawater, 0% seawater ＋ N （7.5 mmol L-1 NaNO3）, 10% seawater ＋ N （7.5 mmol L-1 NaO3）, and 25% seawater ＋ N （7.5 mmol L-1 NaNO3）, was carried out to study the effect of nitrogen addition on the growth and physiological and biochemical characteristics of Jerusalem artichoke （Helianthus tuberosus） seedlings under seawater stress. The 10% seawater stress treatment had the least effect on plant growth while at 25% seawater growth was significantly inhibited. The malondialdehyde content and electrolyte leakage in leaves under 10% seawater were similar to those of the control, but significantly higher under the 25% seawater stress. The activities of superoxide dismutase, peroxidase and catalase in the leaves increased concomitantly with increasing seawater concentration and time. Proline and soluble-sugars in the leaves and Na^＋, K^＋, and Cl- contents in shoots and roots increased significantly with the concentration of seawater increasing. Nitrogen addition resulted in increasing fresh and dry weights of shoots and roots compared with seawater treatment without N. Nitrogen supplementation also significantly enhanced the activities of antioxidant enzymes in leaves. Addition of N to seawater enhanced the contents of proline and soluble-sugars in the leaves and K^＋ and total-N in the aerial parts and roots of H. tuberosus, but it resulted in declined concentrations of Na^＋ and Cl- in the aerial parts and roots. Nitrogen addition ameliorated the toxicity of seawater by improving the antioxidative enzymes, accumulating of proiine and soluble-sugars, and altering the distribution of inorganic ions in H. tuberosus.

Effect of NO3--N enrichment on seawater stress tolerance of Jerusalem artichoke (Helianthus tuberosus)

Thirty-nine rhizobial isolates were isolated from the root nodules of Glycyrrhiza uralensis and Glycyrrhiza glabrca,growing in the arid and semiarid regions of northwestern China,to test their taxonomic position and stress tolerance and to select one promising putative inocnlant strain for further studies.On the basis of 113 physiological and biochemical characteristics,the isolates were clustered into three groups.One isolate CCNWGX035 was found to have high tolerance to NaCl,pH,and temperature.By sequencing the 16S rDNA,isolate CCNWGX035 was placed in genus Mesorhizobiurm.Nodulation tests demonstrated that the isolate not only formed nitrogen-fixing nodules on its original host plant Gly-cyrrhiza glabra,but also on Sophora viciifolia,Lotus cornieulatus,Trifolium reperts,Melilotus suaveolens,and Sophora alopecuroides.On the basis of sequence analysis of the nodA gene,isolate CCNWGX035 was closely related to strains of the genus Mesorhizobiurm,exhibiting some novel characteristics of root nodule bacteria.