Studies On Physiological Ecology, Nitrogen Fixation Activities And Nodule Endophytes Of Red Alder

As a lowland species, red alder (Alnus rubra) is most often observed along the northern Pacific coast. This species is desired for soil nutrient enhancement, good associated species, and the major commercial hardwood tree species. Thereby we carefully studied the species, focusing not only on introduction, cultivation, propagation, growth, and photosynthesis under field conditions, but also on effects of nodulation on nitrogen forms and phosphorus levels, and on activities of nitrogen fixation. The ultrastructure and cytochemical localization of calcium and ATPase activities in the root nodules from red alder was also investigated in detail. Isolation and culture characteristics of the endophyte Frankia from root nodules of A. rubra and other nitrogen fixing trees were observed in this study. Moreover, we compared the differences of growth, morphology and physiological characteristics of two endophyte frankia strains from A. rubra and A. cremastogyne. The conclusions are as follows:Key technologies of sowing and seedling raising of red aler were recognized including the following aspects: depth and time, coverage of nursery bed, management of moisture, and so on. Field Experiments indicated that seedlings of red alder had capacity to survive in hot Summer and cold Winter in Nanjng.Based on the cutting techniques of epicomic branches and mature branches, we determined the contents of endogenous hormones at different time points (0d, 20d, 30d, 37d, 42d, 45d) during rooting process of mature branch cutting. Initial and final values of different endogenous hormones in the cuttings within the period were listed here: 106.66 and 162.02 ng/g for IAA, 16.62 and 25.37 ng/g for GA1/3, and 8.2 and 22.23 ng/g for ZR. The full data demonstrated that the levels of IAA,GA1/3,ZR presented a tendency towards"up-down-up", with the valley value at the 37th day. The ABA levels, 176.54 and 150.02ng/g for the initial and final values, showed an opposite tendency towards"down-up-down", with the peak value at the 37th day.A four-year successive observation on red alder growth in two experiment fields indicated that significant growth was achieved and sexual maturity was mostly reached within four years. At the end of the fourth year, growth increment, measured by stem height and ground diameter, of red alder was highly variable, e.g. 1.5～7.0 m for height and 2.13～9.45 cm for diameter in Nanling, Anhui, while 2.1～5.3 m for height and 2.68～10.20 cm for diameter in Liuhe, Nanjing. The growth data of two-year old red alder showed that the seasonal growth rhythms of height and diameter increment both took on a curve of"S"-form. These results demonstrated that as a fast-growing species, red alder was successfully introduced and seemed to grow well in the two places.The seasonal and diurnal variations of net photosynthetic of two-year-old seedlings in red alder fields were characterized by the following two patterns, a variation curve of single peak on Apr.24 (13.94μmol/m2?s), Oct.10 (16.64μmol/m2?s) and Nov.20 (10.28μmol/m2?s), as well as a variation curve of double peaks at 11:00 am and 15:00 pm on Jun.11 (13.7 and12μmol/ m2?s ) and at 9:00 am and 15:00 pm on Aug.9 (17.7 and 16.85μmol/m2?s). The transpiration rates varied dramatically among seasons. The diurnal variation curves showed a single-peak pattern with a peak value of 4.921μmol/m2?s. By means of correlation analysis and stepwise multi-regression analysis, the multi-correlation among net photosynthetic rate (Pn) and transpiration rate (Trmnol), with meteorological factors, for example, quanta flux density (QFD) and physio-ecological factors such as conductance to water (Cond), were also assessed. The relation equation was established in this paper.Compared to the control of non-nodulation, red alder nodulation significantly improved growth rate and biomass. Remarkable increase was found in the contents of chlorophyll and soluble protein, and nitrate nitrogen, as well as activities of nitrogen reductase and glutaminase. With the application of foliage fertilizer of non-nitrogen Hoagland nutrition, the red alder with nodule roots had better effects on physiological and growth state than the non-nodulation plants spraying mixed or nitrate nitrogen Hoagland fertilizer. Phosphorus liquid fertilizer without nitrogen also promoted growth of red alder. These data supported good activities of nitrogen fixation in red alder.Observation of transmission electron microscopy (TEM) demonstrated that reaction grains of calcium and ATPase had identical location in nodule root cells. These grains were generally located on the cytoplasm membrane, starch periphery, plasmalemma invagination, and wall ingrowth in the non-endophyte cells. In the endophyte cells, however, the positions of reaction grains were different, depending on development stages of endophytes.Thirty three strains were obtained from root nodules of five species, and twenty three strains of them were studied focusing on structure observation and growth state analysis. These observed strains were eight strains from A. rubra, seven from A. cremastogyne, four from A. trabeculosa and four from Myrica rubra.The strains of LH002 and NL001 had characters as follows: strong adaptability, multiple utilization approaches of carbon sources, broad ranges of pH value (6～12.8 for LH002 strain and 4～12 for NL001 strain). On the other hand, these strains could survive at a high concentration (5%) of sodium chloride. Therefore, both strains had high potential application value.