Multiple shoot regeneration from root organ cultures of Populus alba x P. grandidentata

Excised roots of various ages from Crandon and Hansen clones of Populus alba x P. grandidentata were tested for their regeneration capacity. Sixty-day-old excised roots that contained root tips were found to be most suitable. The highest number of shoots (an average of 111 shoots/root segment with Crandon and 98 with Hansen) was obtained by adding 22M and 14M zeatin to the medium, respectively. The two clones of hybrid poplar responded similarly to growth regulator treatments; however, the number of shoots produced was greater from the root organs derived from Crandon clones. Regenerated shoots were rooted in basal Woody Plant Medium without any growth regulators. Successful transplantation into soil and growth was achieved with all plants.     

Effect of irradiance and plant age on the dimensions of the growing shoot of poplar

Populus euramericana (Dode) Guinier cv. Robusta plants were cultivated at irradiances of 7.5, 15 and 30 W m⁻² (32.5, 65 and 130 μmol m² s⁻¹), 400–700 nm at 22°C and a relative humidity between 40 and 60% on a gravel culture subirrigated with Hoagland's nutrient solution. The basal diameter of the growing shoot, a measure of the number of apical cells participating in growth, increased proportionally to irradiance and was correlated with mature leaf length. The development of the length of the growing shoot (L_gs) depended also on the nutritional status of the (young) shoot. L_gs was strongly correlated with the rate of height growth.     

Effects of water and nitrogen interaction on net photosynthesis, stomatal conductance, and water-use efficiency in two hybrid poplar clones

We examined the interactions of water and nitrogen availability by subjecting two Populus clones. Tristis and Eugenei, to five soil moisture and three soil nitrogen levels. Nitrogen application significantly increased net photosynthesis and stomatal conductance of flooded Eugenei and Tristis. The onset of flooding caused partial stomatal closure. Net photosynthesis significantly declined after a longer flooding period. Emergence of adventitious roots on the submerged portions of stems in both clones seemingly helped net photosynthesis fully recover in Eugenei and partially recover in Tristis. Under the progressive drought conditions, stomatal conductance was more sensitive to drought than net photosynthesis in both clones. Addition of nitrogen to progressively drying soil induced more stomatal closure in both clones. The highest water-use efficiency was found on the high-N/severe drought zone for Eugenei, whereas it was found on the high-N/mild to moderate drought zone for Tristis.     

Toxicity toChrysomela tremulae (Coleoptera: Chrysomelidae) of transgenic poplars expressing a cysteine proteinase inhibitor

The aim of this study was to test the potential of proteinase inhibitors to controlChrysomela tremulae, a beetle that causes severe damage in young plantations and in short-rotation intensive culture (SRIC) of poplar. As a first step, cysteine proteinases were determined to be the major digestive proteinases ofC. tremulae and oryzacystatin OCI, a cysteine proteinase inhibitor, was shown to inhibit this activityin vitro. The gene encoding OCI was introduced into poplar (Populus tremula ×P. tremuloides) and transgenic plants expressing OCI at a high level were selected. Feeding tests on these transgenic plants demonstrate the toxicity of OCI-producing poplar leaves againstC. tremulae larvae.J.C. Leplé and M. Bonadé-Bottino contributed equally to the research presented in this paper.     

连作土壤中施加球毛壳ND35菌肥对杨树生理特性的影响

在山东农业大学林学实验站杨树连作土壤中施加不同剂量(0.17、0.33、0.67、1.00、1.33和1.67 g·kg^-1)的球毛壳ND35菌肥,测定不同处理下一年生杨树叶片的光响应过程、叶绿素荧光以及叶黄素循环等光合生理生化指标,研究球毛壳ND35菌肥对杨树根系和光合生理性能的影响.结果表明: 随连作土壤中菌肥含量的增加,杨树叶片的叶绿素含量(Chl)呈增加趋势,电子传递速率(ETR)、净光合速率(P_n)、量子效率(Φ)、硝酸还原酶(NR)活性以及根系活力等生理指标均呈先增加后降低的趋势,依赖于叶黄素循环的光合热耗散呈降低趋势,而非光化学淬灭(NPQ)呈先降低后增加的趋势.在土壤施加菌肥剂量0.67和1.00 g·kg^-1处理时,光合机构的过剩光能减少,向光化学反应方向分配的光能增多,光能利用效率提高.在连作土壤中施加适量(0.67～1.00 g·kg^-1)的球毛壳ND35菌肥,能在一定程度上提高杨树的根系生理活性,提高杨树叶片对光能的利用效率,有利于改善杨树叶片的光合机构运转状态,提高叶片的光合作用效率.     

辽东栎林内不同小生境下幼树植冠构型分析

以黄土高原黄龙山林区辽东栎林内3个小生境（林下、林隙、林缘）下辽东栎天然更新幼树为研究对象,采用典型抽样法对辽东栎幼树侧枝、叶片和树冠的空间分布状况以及生物量分配状况进行调查分析,探讨微生境与幼树植冠构型特征的关系,明确辽东栎幼树对不同小生境的适应策略,为栎林经营和林分结构优化提供理论依据。结果显示：（1）3种生境下辽东栎幼树构型发生了可塑性变化,林下幼树树冠层次比较单一,林隙与林缘的幼树树冠层次更加丰富。（2）由林下至林缘,幼树的树高、枝下高呈逐渐减小的趋势,而地径变化趋势与之相反;幼树的冠幅、树冠面积、树冠率呈先增加后减小的趋势,并且林下与林隙、林缘的差异显著;幼树的总体分枝率、逐步分枝率、枝径比呈先增加后减小的趋势。（3）3种生境下,幼树的一级枝的枝长、直径与倾角随着树高的增加而呈减小的趋势,但3种生境的差异不显著;林下一级枝主要分布在冠层中上部,而林隙与林缘一级枝主要分布在冠层中下、中上部。（4）由林下至林缘幼树叶长、叶宽、单叶面积和比叶面积逐渐降低,而单株叶数、叶总面积、叶面积指数呈先增大后减小趋势;与其他2种生境相比林下叶片分布趋于冠层上部。（5）幼树地上部分生物量中林下主干生物量占83%,枝和叶生物量只占17%;而林隙与林缘虽然各部位生物量有所差异但比例基本一致,其中主干占66%左右,枝和叶生物量占34%左右。研究表明,林隙生境下幼树的构型优于林缘和林下生境,在今后栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化提供有利条件。     

Leaf size serves as a proxy for xylem vulnerability to cavitation in plantation trees

Hybrid poplars are an important renewable forest resource known for their high productivity. At the same time, they are highly vulnerable to water stress. Identifying traits that can serve as indicators for growth performance remains an important task, particularly under field conditions. Understanding which trait combinations translate to improved productivity is key in order to satisfy the demand for poplar wood in an uncertain future climate. In this study, we compared hydraulic and leaf traits among five hybrid poplar clones at 10 plantations in central Alberta. We also assessed the variation of these traits between 2‐ to 3‐year‐old branches from the lower to mid‐crown and current‐year long shoots from the mid to upper crown. Our results showed that (1) hybrid poplars differed in key hydraulic parameters between branch type, (2) variation of hydraulic traits among clones was relatively large for some clones and less for others, and (3) strong relationships between measured hydraulic traits, such as vessel diameter, cavitation resistance, xylem‐specific and leaf‐specific conductivity and leaf area, were observed. Our results suggest that leaf size could serve as an additional screening tool when selecting for drought‐tolerant genotypes in forest management and tree improvement programmes.