查看更多>>摘要：We analyzed the partition of nocturnal sap flow into refilling of internal water storage and transpiration in Acacia mangium. Sap flow of trees was monitored continuously with Granier's sensors for estimating the whole-tree transpiration. Possible night transpiration and stomatal conductance at the leaf level in the canopy were measured with a LI-6400 photosynthesis measuring system. For nocturnal leaf transpiration and stomatal conductance were weak, nocturnal sap flow of mature A. mangium trees was mainly associated with water recharge in the trunk. No significant change in night water recharge of the trunk was found at both seasonal and inter-annual scales. Morphological features of trees including diameter at the breast height (DBH), tree height, and canopy size could explain variances of night water recharge. Furthermore, although the contribution of nocturnal sap flow to the total transpiration varied among seasons and DBH classes, the error caused by night water recharge on whole-tree transpiration was negligible.
查看更多>>摘要：Using the PMS pressure chamber and isotope mass spectrometer (MAT-252), the leaf juice of Acacia mangium was obtained, and the carbon isotope discrimination (△) representing the most recently fixed carbon in the juice was determined. At the same time, the water-use efficiency of A. mangium was estimated. The results indicated that the carbon isotope ratio in the air of forest canopy (δa), 10m high above ground averaged -7.57 1.41‰ in cloudy days, and - 8.54±0.67 ‰ in sunny days, respectively. The diurnal change of the carbon isotope ratio in the photosynthetic products of the leaf juice (δp) was of saddle type in cloudy days, but dropped down from morning to later afternoon in sunny days. A strong negative correlation betweenδp and leaf-to-air vapor pressure deficit (D) was observed in sunny days, but a slight change inδp, was found in cloudy days. Theδp also decreased with decreasing leaf water potential (ψ), reflecting that water stress could cause the decrease ofδp. The carbon isotope discrimination of the leaf juice was positively correlated with the ratio between intercellular (Pi) and atmospheric (Pa) partial pressure of CO2. For A. mangium, the isotope effect on diffusion of atmospheric CO2 via stomata was denoted by a = 4.6 %>, and that in net C3 diffusion with respect to Pi was indicated by b = 28.2 ‰. The results were in reasonable accord with the theoretically diffusive and biochemical fractionation of carbon isotope. It was defined that carbon isotope discrimination of photosynthetic products in A. mangium leaf juice was in proportion to that from photosynthetic products in dry material. The water-use efficiency estimated by the carbon isotope discrimination in leaf juice, fit well with that measured by gas exchange system (R2 = 0.86, p< 0.0001). The application of leaf juice in measuring the stable carbon isotope discrimination would reduce the effects of fluctuating environmental factors during the synthesis of dry matter, and improve the eco-physiological studies on carbon and water balance when scaling from the plant to canopy in the fields.
查看更多>>摘要：We studied ion distribution in roots and the growth of Cyclocarya paliurus seedlings of three provenances, Huangshan in Anhui, Jiujiang in Jiangxi and Kunming in Yunnan, under conditions of 0, 1,3 and 5 g/L NaCI stress using X-ray microanalysis. Results show that under NaCI stress of 3 and 5 g/L, the relative contents of Na+ and Cl in root tissues increased, while the relative contents of K+, Ca2+ and Mg2+ decreased. With an increase in salinity, the relative content of Na+ in the epidermis and cortex of the root increased, while the relative content of Cl in the stele and cortex of the root increased markedly. Thus, ions in the root tissues were unbalanced and the ratios K7Na+ and Ca27Na+ decreased, while Na7(K++ Na++Ca2++Mg2+) increased. The decrease of the K+/Na+ ratio and the substantial increase of Cl" in root tissues contributed to a decline in seedlings survival and reduced the increments for seedling leaf area, height, basal diameter as well biomass. Our preliminary conclusion is that the level of salt tolerance for the tested provenance seedlings was in the order of Huangshan > Kunming > Jiujiang, and the threshold of salt tolerance for C. paliurus seedlings was about 1 g/L.
查看更多>>摘要：In order to investigate the protein features of an NBS gene (PtDRGOl, EF157840) isolated from Populus tomentosa Carr., the full-length open reading frame was fused into a prokaryotic expression vector pGEX-KG. PCR analysis and double endonuclease digestion showed that the recombinant vector was successfully constructed and transferred into an expression host E. coli strain XA90. It was indicated by SDS-PAGE analysis that IPTG treatment successfully induced the expression of a fusion protein of about 79 kD, which was consistent with the predicted value. In addition, the prokaryotic expression system was also optimized. The result suggests that lmmol/L IPTG treatment for 4h at 37 C was most effective, and the product was predominately soluble and not extra-cellular secreting. Moreover, the fusion protein was purified with an affinity chromatography column using Glutathione Sepharose 4B. This work will lay a foundation for further studies on biological functions of the PtDRGOl gene.
查看更多>>摘要：By using the methods of random amplified polymorphic DNA (RAPD) and bulked segregate analysis (BSA), we identified markers that are linked to the sex determination in the dioecious Populus tomentosa. Male and female bulks were created through rough mixing equal amounts of its five individual DNA. A total of 88 primers were screened. Twelve primers produced clear patterns with at least one band that appeared to be polymorphic between the two bulks. Subsequently, five male and female individuals were analyzed with those 12 primers, and only S60 (ACCCGGTCAC) could generate a common 1800bp DNA fragment in all five male individuals and male pool but not in any female individuals. It can be concluded that the gender of P. tomentosa is most likely connected to the S60-1800bp DNA fragment and RAPD markers. S60, therefore, can be used for selecting the gender of P. tomentosa.
查看更多>>摘要：Tetraploid Robinia pseudoacacia was used as a main test material and diploid R. pseudoacacia was used as the control. The indices of shape, physiology and biochemistry, photosynthesis and anatomic structure of the young plants were investigated under salt stress (NaCl and Na2SO4). The treatment time was 30 d with an interval time of 7 d. Before and after treatment, the indices were measured. Results show that: 1) the growth of diploid R. pseudoacacia inhibited an evident symptom of salt damage and the leaf moisture content was lower under salt stress than that of control. But the tetraploid R. pseudoacacia was contrary. 2) The relative electric conductivity and proline (Pro) of tetraploid R. pseudoacacia increased slightly and had no significant difference compared with its control, which was contrary to diploid R. pseudoacacia. At the same time, three protective enzymes including perocidase (POD), superoxide (SOD) and catalase (CAT) kept higher activities at a post stage of salt stress to tetraploid R. pseudoacacia, which enhanced its anti-salt characteristics. Diploid R. pseudoacacia was sensitive to salt and had contrary information. 3) Salt stress had little influence to photosynthesis of tetraploid R. pseudoacacia. The net photosynthetic rate (Pn) and intercellular CO2 concentration (CO had no significant changes, but those of diploid R. pseudoacacia decreased singificantly. 4) After salt stress, the anatomic structure of tetraploid R. pseudoacacia had a positive reaction, including the palisade parenchyma of diachyma, was prolonged and arranged more tightly. The spongy parenchyma was shrunk and was arranged tightly, which was contrary with diploid R. pseudoacacia. These data demonstrate that tetraploid R. pseudoacacia had superior anti-salt performance.
查看更多>>摘要：To explore the effects of plant hormones levels excreted by ectomycorrhizal (ECM) fungi on the growth of poplars, Populus x euramericana cv. NL-895 seedlings were inoculated with nine species of ECM fungi. We investigated the status of ectomycorrhizal formation and the effects of these fungi on poplar growth, and using the HPLC method, we measured the contents of four kinds of plant hormones, indole acetic acid (IAA), zeatin (Z), gibberellin (GA) and abscisic acid (ABA) in both the culture filtrate and the mycelium of these fungi. The results showed that the effects of nine ECM fungi on the growth of poplar NL-895 varied. The inoculated seedlings, whether or not obvious mycorrhizas were developed, grew better than those non-inoculated ones. All nine ectomycorrhizal fungi excreted the four plant hormones, but at different levels. The hormone contents in culture filtrate were higher than that in mycelium, which showed a definite relationship with poplar growth. Significantly, correlation analysis suggested the height and stem diameter of the poplar were positively correlated with zeatin contents in the mycelium, and were negatively correlated with the levels of ABA or IAA in the mycelium.
查看更多>>摘要：We studied the frost hardiness (FH) in stems and needles of different Pinus bungeana provenances during frost hardening by means of electrical impedance spectroscopy (EIS) and conventional electrolytic leakage (EL) and compared the regression equations of the two methods in order to optimize the EIS method for studying FH on plants. During frost hardening, EIS and EL were applied to one-year old stems and needles of P. bungeana in an 8-year provenance field trial at the Thirteen Tombs Nursery in Beijing within the provenances of Mangshan of Beijing, Liangdang of Gansu and Xiaoyi of Shanxi provinces, China. A double-DCE model and Model-A were used, respectively, for the EIS analysis of stems and needles that were not exposed to a controlled freezing treatment. After controlled freezing tests, the FH of stems and needles were assessed by EIS and EL. Without controlled freezing tests, the relaxation time (τ1) of stems and the specific intracellular resistance (ri) of stems and needles displayed a statistically significant correlation with FH (R2 =0.79-0.86); after controlled freezing tests, specific extracellular resistance (re) of the stems and needles, the cell membrane time constant (τm) of needles displayed an even higher correlation with FH (R2 = 0.92-0.94). There were significant relationship between EIS and EL in assessing the FH of stems and needles of P, bungeana, but EIS underestimated FH more than EL did. EIS is one of the more promising methods for assessing FH, especially without employing a controlled freezing test.
查看更多>>摘要：The improvement of wood surface wettability can clearly improve bonding properties, as well as enhance physical and mechanical properties of wood composites. In our investigation, the microwave plasma (MWP) technique was adopted to treat the surface of common teak. The treatment effect was evaluated by measuring the contact angles of liquids and calculating the free surface energy. The results show that the modification effect improved when the sample was located 120 mm from the resonance cavity, rather than at 80 mm. A MWP treatment over a short span of time is useful to lower the contact angles and improve the surface wettability considerably. The range of decreasing contact angles,tested by water, could reach 74% at a distance of 120 mm.
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