提高华北落叶松造林成活率的关键技术环节

成活率是检验造林成败的一个关键技术指标,对影响华北落叶松成活率的几大关键因素进行了分析,认为良种壮苗和认真栽植是提高造林成活率的关键因素。     

一品红不同品种叶片叶绿素荧光特性比较

 利用叶绿素荧光技术测定了一品红4个品种‘金多利’、‘圣诞天使’、‘索诺拉飞雪’、‘旗帜’叶片光强依赖的叶绿素荧光特性。结果表明: ‘金多利’初始荧光( F_o ) 、最大荧光( F_m ) 和可变荧光( F_v ) 值极显著高于其它3个品种。在各个光强( PAR, 0～2 171μmol·m^{- 2} ·s^{- 1} ) 下, 表观电子传递速率( rETR) 、实际光化学效率(Yield) 和光化学淬灭( q_P ) 的变化趋势一致, 均为‘金多利’ > ‘圣诞天使’ > ‘索诺拉飞雪’ > ‘旗帜’, 在高PAR下这种差异更明显。拟合参数最大潜在相对电子传递速率( rETR_max ) 、半饱和光强( Ik) 和光抑制参数(β) 也同rETR等具有一致变化。说明‘金多利’有较高的PSⅡ活性, 耐强光; 而‘旗帜’则光化学效率较弱, 高光强下易受光抑制。     

Changes in soil bacterial community structure and microbial function caused by straw retention in the North China Plain

ABSTRACT

The effects of straw retention on soil bacterial community structure, microbial function, and biochemical properties were assessed. Terminal restriction fragment length polymorphism (T-RFLP) and community-level physiological profile (CLPP) assays were used to assess the bacteria community structure and microbial function respectively. Treatments included straw removal with conventional tillage (CT), straw retention with conventional tillage (SRCT) and straw retention with no tillage (SRNT). SRCT and SRNT significantly (p < 0.05) increased soil organic carbon by 8.9% and 9.7%, and microbial biomass carbon by 44.7% and 330.8%, respectively, compared with CT. T-RFLP analysis indicated that straw retention had no favourable effect on soil bacterial diversity, and SRCT significantly (p < 0.05) decreased bacterial diversity compared to CT. Among the three treatments, SRNT had the highest activity of urease, invertase, cellulase, and β-glucosidase. SRCT significantly (p < 0.05) increased the activity of invertase and β-glucosidase compared to CT treatment. CLPP analysis showed that microbial functional diversity was significantly (p < 0.05) increased by straw retention. Enzyme activity and microbial functional diversity were not correlated with bacterial diversity. Therefore, according to this study, SRNT is a better farming practice because it improves soil fertility and biological quality.     

养分胁迫对油菜碳酸酐酶活性的影响

对养分胁迫下油菜中碳酸酐酶活性和叶绿素含量的变化进行了研究。结果表明:缺乏氮磷钾素时,油菜的碳酸酐酶活性和叶绿素含量均有所下降;氮磷钾缺乏对油菜的生长也有不同程度的影响。     

Feeding selectivity of the marine ascidian Styela clava

The sessile suspension feeding ascidian, Styela clava , plays an important role in the functioning of estuarine systems. The feeding selectivity of S. clava was examined using standard physiological techniques in terms of particle sizes and diet concentrations. Styela clava increased its retention efficiency (the proportion of available particles retained in ascidian) with increasing particle size at a lower diet concentration [expressed as particulate organic matter (POM)] from 2.11 to 10.06 mg POM L⁻¹, and the highest retention was reached for 5–20 μm particles. With increasing diet concentration to 20.12 mg POM L⁻¹, S. clava retained small particles (<3.5 μm) more efficiently and large ones (>15 μm) less efficiently. The selectivity of ascidian with different sizes was similar at the same concentration. At every diet concentration, larger ascidians retained more 5–20 μm cells than the smaller ones. All these results indicate that S. clava possesses a particle selection mechanism that may affect the zooplankton communities to a certain degree.     

马尾松和红锥叶片解剖和光合对穿透雨减少的响应

目的 探究8 a干旱胁迫条件下树木叶片光合生理特征与叶片解剖结构的响应及二者之间的关系。 方法 在南亚热带选取2种典型人工林（马尾松和红锥）设置林内穿透雨减少的模拟干旱实验,在穿透雨减少8 a后测定叶片气体交换参数、叶绿素荧光参数、叶片解剖特征以及叶片养分（N、P）含量。 结果 （1）穿透雨减少后,马尾松针叶上、下表皮、叶片厚度以及气孔密度显著增加,而红锥仅叶片上表皮厚度显著增加,海绵组织厚度显著降低。（2）马尾松和红锥的气体交换参数（净光合速率Pn、气孔导度Gs、蒸腾速率Tr）、叶绿素荧光参数（光系统Ⅱ最大光化学效率Fv/Fm、实际光化学效率 ΦPSII,表观电子传递速率ETR）以及叶氮、磷含量在穿透雨减少8 a后均未发生显著变化。（3）与马尾松相比,红锥受到的气孔限制（Ls）更大,水分利用效率（WUE）更高,尤其在干季更明显。 结论 马尾松和红锥应对干旱胁迫的策略存在差异,马尾松通过调节叶片解剖结构产生更具耐旱的针叶来应对干旱,红锥则更倾向通过调节气孔（Ls）、提高水分利用效率（WUE）来适应干旱。     

铁皮石斛（Dendrobium catenatum）叶艺形成机制的初探

[目的 ]探究铁皮石斛(Dendrobium catenatum)叶艺形成的分子机制,为培育叶艺兰花品种提供理论基础。[方法 ]以正常铁皮石斛(WT)、叶艺铁皮石斛叶片绿色组织(YYG)、叶艺铁皮石斛叶艺白色组织(YYW)为研究对象,通过显微结构观察、叶绿素及其前体物质含量的测定、叶绿素合成相关基因的qRTPCR定量来探究叶艺形成的分子机制。[结果 ]YYW的总叶绿素含量明显低于WT和YYG,同时其叶绿体细胞结构出现了畸形现象。在叶绿素合成前体物质中,YYW中粪卟啉原Ⅲ的含量显著高于WT和YYG,而原卟啉IX、镁原卟啉IX和原叶绿素酸酯在WT和YYG中的含量则高于YYW。此外,qRT-PCR结果显示:粪卟啉原氧化脱羧酶(DcHEMF)、原卟啉原氧化酶(DcHEMG)、镁螯合酶H亚基(DcCHLH)在YYW中的表达量显著下调。[结论 ]YYW中DcHEMF、DcHEMG和DcCHLH表达量的下调使粪卟啉原Ⅲ无法正常流向叶绿素合成,这导致了其叶绿素含量的下降,是使铁皮石斛叶片出现了叶艺表型的主要原因。     

SiO2纳米颗粒对杉木幼苗生长发育的影响

【目的】近年来,硅对于的植物影响受到人们广泛关注,人们试图将硅确定为植物生长发育的的“必要元素”。因此如何提高植物对硅的吸收利用来增加植物的农艺性状和产量,是当前农业和林业研究的一个重要课题。【方法】以黄枝杉Cunninghamia lanceolata和罗田垂枝杉C.lanceolata var.luotian为材料,采用盆栽的方式,研究施加不同浓度的纳米SiO2颗粒(0、1、2、4 g/盆)对杉木幼苗光合参数、叶绿素荧光、叶片厚度、氮磷钾含量及其分配、生物量累积的影响。【结果】本研究结果显示,SiO2纳米颗粒对杉木根系的生长发育有很大的促进作用,使之能更好的吸收养分,加强了氮磷钾含量的累积。且叶片的厚度也有所增加,在较低的浓度下,气孔导度、光合作用机制、以及光合作用效率增加;地上的生物量也随着施入SiO2纳米颗粒浓度的增加而增加。【结论】我们的实验表明,SiO2纳米颗粒通过促进根系发育加强对营养的吸收和提升叶片厚度,以及提高净光合速率和气孔导度来提高植物的生长机理,进而增加植物的生物量来提升产量。鉴于其对植物生长发育及产量的多种积极影响,硅纳米材料将会为农林植物增产有重要的影响和广阔的前景。