Evaluation of different agroforestry tree species for their suitability in the phytoremediation of seleniferous soils

Seven agroforestry tree species were grown in a clay loam soil treated with different levels of selenate‐Se, viz. 0, 1.25, 2.5 and 5.0 mg/kg supplied through sodium selenate. After 1 year of growth, a progressive decrease in dry matter of leaves, stem and roots was observed with increasing levels of applied Se. However, a significant decrease in dry matter yield was observed only at or above 2.5 mg Se per kg soil and shisham (Dalbergia sissoo) proved to be highly sensitive to the presence of selenate‐Se in the soil. On average, the largest above‐ground and below‐ground biomass was accumulated by arjun (Terminalia arjuna) and the lowest by the acacia tree (Acacia tortillas). The selenium content of leaves, stem and roots of all the tree species increased significantly with increasing levels of applied Se, although a large variation within species was observed. In the stem portion of different trees, the highest concentration of Se was found in dek (Melia azedarach) (5.1 mg/kg) and the lowest in mulberry (Morus alba) (2.6 mg/kg). The efficiency of selenium removal (including leaves, stem and roots) was the highest in arjun followed by eucalyptus (Eucalyptus hybrid) – Clone 10, mulberry, jambolin (Syzygium cumini), dek, shisham and acacia. Effective removal of Se takes place through the stem portion of different trees where it constitutes 30–50% of total Se. Large variation in Se uptake by different tree species suggests that trees vary in their potential for phytoremediation of seleniferous soils. In one growing season, shisham aged 24 years, poplar (Populus deltoides)– Clone G 48 (10 years old) and eucalyptus – Clone 10 (10 years old) could remove 2385, 1845 and 1407 g Se per hectare respectively. Corresponding reductions in Se capital of the soil varied between 24 and 37, 19 and 29 and 14 and 32%, respectively, in the surface layer (0–15 cm) alone or 7–11, 6–9 and 4–7% for the whole soil profile (0–120 cm). Removal further increased to 4207 g Se per hectare under an agroforestry farming system of poplar–mentha/wheat with Se being reduced from 43 to 65% for the surface layer and from 13 to 20% for the whole profile.     

Structural Characteristics and Eco-adaptability of Heteromorphic Leaves of Populus euphratica

The microstructural and ultrastructural traits of three kinds of typical leaves of Populus euphratica Olive, including lanceolate, broad-ovate and dentate broad-ovate leaves, were studied by using electron microscope and optical microscope. The re- sults showed that with the leaves changing from lanceolate shape to dentate broad-ovate shape, their structure obviously tended to be xeromorph: developed palisade tissue, undeveloped spongy tissue, thick cutin layer and sunken stomas. The amount of mitochondria tended to be increased, and the shape of chloroplasts varied from regular spindle to irregular rotundity or oval. The leaves were cov- ered with wax without cilium, and the stomas on the upper and lower epidermis of the leaves opened unevenly. The stomas on the lower epidermis were deeper than those on the upper epidermis under the scanning electron microscope. The results implied that the structural characteristics of the diversiform-leaves of P. euphratica are related to its eco-adaptability.     

杉木积成材薄木贴面工艺初探

采用正交试验法，探讨了杉木积成材薄木贴面的工艺过程。试验结果表明：利用杉木积成材进行薄木贴面．工艺切实可行，奥古曼薄木贴面的较佳工艺参数为：热压温度100℃，热压压力1．0MPa，热压时间4min，涂胶量120g／m^2。     

退耕还林地杨树与龙芽楤木的间作模式

在退耕还林地开展杨树与龙芽楤木间作栽培可有效地发挥林地生产力，消灭空白生态位．同时可增加农民的收入。     

Characterization and Role of Glucose-6-phosphate Dehydrogenase of Populus suaveolens in Induction of Freezing Resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTTred) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTTred, indicating that the purified enzyme probably presented in cytosol of P suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P.suaveolens cuttings were also studied. The results show that G6PDH is characterized by Km value of 360/amol.L^-1 for G6P and 16μmol.L^-1 for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol‘L i except for NADPH and NADH)to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgC12, CaC12 and KC1 (all 1.0 mmol.L^-1) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl2 (1.0 mmol.L-1) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LTs0) of P. suaveolens cuttings during freezing acclimation at -20℃ were investigated. The results reveal that freezing acclimation decreases LTs0 of cuttings, and increases the activity of cytosolic G6PDH compared with control ones,while 2 d of de-acclimation at 25 ~C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT50. Furthermore,the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings.     

Establishment of high frequency shoot regeneration system in Himalayan poplar (Populus ciliata Wall. ex Royle) from petiole explants using Thidiazuron cytokinin as plant growth regulator

Populus species are important resources for industry and in scientific study on biological and agricul-tural systems. Our objective was to enhance the frequency of plant regeneration in Himalayan popla...     

Development of molecular markers to assess the level of introgression of Populus tremula into P. alba natural populations

Morphological traits traditionally adopted to discriminate between Populus alba L. and P. tremula L. have frequently led to misclassifi‐cation of their spontaneous hybrid P. × canescens Sm. Moreover, they may not be of any help in cases of spontaneous backcross phenomena. These limitations can be overcome by molecular markers, which are not environmentally influenced nor subjectively assessed. In this study, the effectiveness of amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers in species and hybrid discrimination was evaluated by analysing a set of reference samples of P. alba, P. tremula and P. × canescens. Species‐specific and species‐indicative AFLPs, as well as diagnostic SSR alleles, were recorded in both P. alba and P. tremula reference samples. The results allowed a clear distinction between the two poplar species and their hybrid. Using these diagnostic markers, a natural population of P. alba trees sampled along the Ticino river basin in northern Italy was analysed, and P. × canescens individuals, intermingled with P. alba trees, were detected.     

转透明颤菌血红蛋白基因杨树的再生及其生长量初步测定

采用农杆菌介导法,将透明颤菌血红蛋白Vitreoscilla hemoglobin(VHb)基因vgb导入银腺杨(Populus alba ×P.glandulosa).以经无菌培养的叶片为外植体,通过450个叶盘与根癌农杆菌(Agrobacterium tumefaciens)LBA4404共培养,将植物双元表达载体pPZV中vgb基因导入银腺杨基因组,经卡那霉素筛选后,共获得60株卡那霉素抗性植株.经PCR特异性扩增和Southern点杂交分析,证明其中52株再生植株基因组DNA中整合了vgb基因.RT-PCR分析结果表明,vgb基因在其中的44个株系中获得表达.在2年温室生长条件下,转基因无性系的外部形态与对照相比无显著差异.但在株高和地径上,有3株转基因无性系较对照植株有明显增加.     

不同苜蓿品种再生草特性分析

小叶杨是黄土高原地区栽植较为广泛的树种之一。通过对不同坡位小叶杨纯林和小叶杨 沙棘混交林中的小叶杨的生长状况的研究，结果表明：坡下位的小叶杨生长良好，郁闭度为30％，树高可达12．67m，而坡中位和坡上位的小叶杨树高仅为5．70m和5．2lm，相差1倍以上。地径、胸径、枝下高和冠幅生长状况表现出同样的趋势；以沟谷地带的小叶杨的生长位为基点，则坡下部、中部和上部的小叶杨的树高和胸径相对生长潜力分别为沟谷小叶杨的77．53％，34．88％，31．88％和75．59％，39．5l％，33．36％；但小叶杨与沙棘混交后，生长表现较为良好；混交林的覆盖度最高、并且具有较高的物种多样性指数，物种较多且分布均匀，具有良好的生态效益。研究表明，小叶杨作为该地区的一个隐域树种，除沟谷等一些水分条件较好的立地外，不宜进行大面积栽植。     

干旱胁迫对小叶杨幼苗生长的影响

[目的]了解小叶杨的抗旱机理,为山西省北部半干旱风沙区小叶杨防护林建设提供科学依据。[方法]通过在山西省苗圃基地盆栽模拟干旱试验,以小叶杨生长过程中的苗木株高和地径,根、茎、叶生物量,叶片相对含水量和水势,净光合速率、蒸腾速率等为生长和生理指标,研究干旱胁迫对小叶杨幼苗生长的影响。[结果]干旱胁迫抑制了小叶杨幼苗的生长,包括地上部分和根系的生长;叶片相对含水量和水势随土壤相对含水量降低而下降;各干旱梯度下CK,T1,T2,T3,T4,T5的净光合速率、蒸腾速率也随干旱梯度加深而降低,但从CK(田间持水量,土壤含水量20.3%)到T3(田间持水量的40%,土壤含水量8.12%)净光合速率和蒸腾速率随干旱梯度加深降幅逐渐较小,并且干旱时也能保持较大的光合速率和蒸腾速率,表明小叶杨具有明显抗旱特性;当土壤水分进一步减少,T4(田间持水量的30%,土壤含水量为6.09%)时小叶杨开始出现干枯现象,T5(田间持水量量的20%,土壤含水量为4.06%)时小叶杨全部死亡。[结论]山西省西南部及其周边地区进行小叶杨造林时,土壤水分应尽量要保持在6.09%(T4)以上。