A New Micropropagation Technology of Tilia amurensis:In VitroMicropropagation of Mature Zygotic Embryos and the Establishment of a PlantRegeneration System

Tilia amurensis is an economically valuable broadleaf tree species in Northeast China.The production of highqualityT.amurensis varieties at commercial scales has been greatly limited by the low germination rates.Thereis thus a pressing need to develop an organogenesis protocol for in vitro propagation of T.amurensis to alleviate ashortage of high-quality T.amurensis seedlings.Here,we established a rapid in vitro propagation system forT.amurensis from mature zygotic embryos and analyzed the effects of plant growth regulators and culture mediain different stages.We found that Woody plant medium(WPM)was the optimal primary culture medium formature zygotic embryos.The highest callus induction percentage(68.76%)and number of axillary buds induced(3.2)were obtained in WPM+0.89μmol/L 6-benzyladenine(6-BA)+0.46μmol/L kinetin(KT)+0.25μmol/Lindole-3-butryic acid(IBA)+1.44μmol/L gibberellin A_(3)(GA_(3)).The multiple shoot bud development achievedthe highest percentage(83.32%)in the Murashige and Skoog(MS)+2.22μmol/L 6-BA+0.25μmol/L IBA+1.44μmol/L GA_(3).The rooting percentage(96.70%)was highest in 1/2 MS medium+1.48μmol/L IBA.Thesurvival percentage of transplanting plantlets was 82.22%in soil:vermiculite:perlite(5:3:1).Our study is the firstto establish an effective organogenesis protocol for T.amurensis using mature zygotic embryos.

Ectomycorrhizal communities associated with Tilia amurensis trees in natural versus urban forests of Heilongjiang in northeast China

The deciduous linden tree （Tilia amurensis Rupr.） is protected at National Level II in China as a species of ecological and economic importance. The objective of this study was to assess and compare the ectomycorrhizal communities associated with T. amurensis in natural versus urban forests of central Heilongjiang Province. The percentage of T. amurensis colonisation by ectomycorrhiza was more than 60 % in urban forests, compared to 34-49 % in natural forests. Use of a combi- nation of morphological and molecular methods docu- mented 18 ECM （ectomycorrhizal） types among three sites; 12-13 ECM species were identified in the natural sites versus 9 species in the urban site. Four ECM species （Boletus sp., Tuber sp., Inocybe sp.2, Leccinum sp.1） were the dominant mycorrhizal symbionts, and Cenococcum geophilum and Russula sp. were found only in the natural forests.

Biomass allocation and assimilation efficiency of natural Tilia amurensis samplings in response to different light regimes

Biomass allocation and assimilation efficiency of natural Amour linden (Tilia amurensis) samplings in different light regimes were analyzed in the paper. The results showed that shoot increment of samplings in gap was the highest and that of samplings under canopy was the least. Samplings in gap expressed apical dominance strongly but samplings in full sun and under canopy behaved intensive branching. Lateral competition or moderate shading was favored to bole construction. The patters of biomass allocation of samplings in different light environment were rather similar. The biomass translocated to stem was more than that to other organs, and about one half of photosynthate was used to support leaf turn over. On the contrary, photosynthates of samplings in full sun were mostly consumed in leaves bearing and energy balancing. The carbon assimilation for leaves of samplings in gap was the most efficient, and more carbons were fixed and translocated to non-photosynthetic organs, especially to stemwood.

Fallen wood decomposition of Pinus koraiensis and Tilia amurensis

Fallen wood decomposition rate ofPinus koraiensis andTilia amurensis in broadleaved Korean pine forest was studied in this paper. The result showed that decomposition rate of fallen wood was different from that of little diameter wood and coarse woody debris for the same tree species. Fallen wood decomposition was generally rotten from outside to inside. And decomposition speed of fallen woods was different according to tree species and site, and it was also related to diameter of fallen woods. Decomposition depth ofTilia amurensis fallen wood for 17 years was 14 cm, but that ofPinus koraiensis in the same condition was less than 7 cm.Tilia amurensis was decomposed faster thanPinus koraiensis. For same tree species, if the diameter was small, the decomposition speed was quick.

Study on Tissue Culture and Rapid Propagation of Tilia amurensis

To explore the establishment of a tissue culture and rapid propagation system of Tilia amurensis,the effects of basic medium and concentrations and ratios of plant growth regulators on tissue culture and rapid propagation of T.amurensis were studied.The results showed that 1/2 MS medium was the most suitable proliferation medium,and the proliferation coefficient could reach 13.5 after adding 0.05 mg/L 6-BA and 0.03 mg/L IBA;MS medium was the most suitable medium for strong plantlets and rooting,and the best medium for strong plantlets was MS+0.1 mg/L 6-BA+0.1 mg/L IBA+0.03 mg/L GA_(3),with which the average plantlet height reached 5.15 cm;and the best rooting medium was MS+1.0 mg/L6-BA+0.05 mg/L NAA,with which the rooting rate was 93.3%and the number of roots was 5.7 roots.

光照和地下竞争对林冠下人工更新紫椴苗木形态和生物量分配的影响

以次生林林冠下人工更新的2年生紫椴苗木为研究对象,设置2种光照(强光(High light,HL,林隙),弱光(Low light,LL,林冠))和4种排除地下竞争(施肥(F)、切根(T)、切根加施肥(T+F)、对照(CK))处理,测定紫椴苗木形态特征和生物量分配,探究光照和地下竞争对林下人工更新紫椴苗木的影响。结果表明,1)切根和施肥对紫椴苗木苗高和地径生长量有显著的促进作用,其中T和T+F处理对苗木苗高和地径生长量的提高更显著,光照对紫椴苗木苗高和地径生长量无显著影响。2)紫椴苗木生物量和比叶重均受到光照和排除地下竞争措施交互作用的显著影响。8个处理组合中,HL下T和T+F处理对紫椴苗木的生物量积累和比叶重均有显著的促进作用,苗木生物量和比叶重均是HL下T+F处理的最大值,其次是HL下的T处理,LL下的CK处理苗木生物量均高于HL下的CK处理。3)T+F和T处理显著提高了紫椴苗木细根根长、根表面积和根体积,T+F处理较T处理增加更显著,光照对紫椴苗木细根形态无显著影响。综上,林冠下人工更新紫椴苗木时,林冠下适度遮荫的光环境更适宜紫椴苗木生长和更新,在林隙这种较强的光环境下进行紫椴人工更新时,应辅以切根或者切根加施肥的抚育措施,减少上层木根系对土壤资源的竞争以促进苗木生长。

CO_(2)升高和增温没有稀释椴树叶片氮浓度却降低了叶片的光合能力

深入理解CO_(2)升高和全球变暖对植物的影响是预测植物适应性的关键。本研究以温带阔叶耐荫树种椴树(Tilia amurensis)幼苗为试验材料,研究了当前CO_(2)浓度和气温组合处理(CC)与预测的未来气候条件下CO_(2)升高和增温组合处理(FC)对植物光合驯化的影响模式。结果发现,FC处理促进了椴树地上部分的生长,降低了叶片的光合能力(最大羧化速率和最大电子传递速率),也降低了椴树光合作用生化限制中从羧化限制向电子传递限制过渡点的光合速率。FC处理没有改变叶片氮浓度,但是提高了单株叶片的含氮量和光合氮素利用效率。这些结果表明,在椴树适应未来气候条件中发挥重要的作用的可能是叶片的氮素利用效率,而非其光合能力。本研究为理解椴树的光合驯化特征提供了新的见解,研究结果也可以用于预测椴树在未来气候条件下可能的表现。