长白山阔叶红松林不同演替阶段林下红松幼苗能量与养分季节动态

为了解林下红松幼苗生长和养分存储季节动态,以长白山原始阔叶红松林(原始林)和次生杨桦林(次生林)林下2年生红松幼苗为对象,研究林下光合有效辐射(PAR)、幼苗生物量、非结构性碳水化合物(NSC)、全氮(N)和全磷(P)等指标的季节变化,分析两林分林下光照的季节动态及其差异对红松幼苗生长和养分积累的影响。结果表明: 原始林和次生林林下月PAR累积量季节变化都呈“双峰”型,夏季为郁闭期,两林分林下光线弱。春季和秋季为阔叶树无叶期,林下光照条件变好,且次生林林下光照明显好于原始林;原始林和次生林红松幼苗的生物量、NSC、全N和全P浓度的季节动态与林下光照的季节变化基本一致,在春季和秋季表现为显著增加,在夏季呈下降趋势。春季幼苗的淀粉浓度增加,夏季淀粉和可溶性糖浓度均逐渐降低,到8月达到最低值,秋季可溶性糖浓度显著升高。春季和秋季次生林林下幼苗的生物量和NSC浓度整体上均显著高于原始林,而夏季两林分差异不显著。因此,春季和秋季的林下光照条件差异是影响原始林和次生林中红松幼苗养分积累和生长更新差异的主要原因。     

Cu2O纳米颗粒对小麦根系形态及遗传毒性的影响

为了阐明Cu₂O纳米颗粒(NPs)暴露对植物根系的毒性效应,本研究以小麦品种‘周麦18’为材料,采用水培试验方法,研究了10、50、100和200 mg·L^-1浓度的Cu₂O-NPs对小麦幼苗生长、根系活性、形态结构及细胞遗传学毒性的影响。结果表明: 不同浓度的Cu₂O-NPs降低了小麦幼苗的根芽长度、鲜重、根活性和根冠比,增加了初生根的数量;随着Cu₂O-NPs浓度的升高,幼苗根伸长区缩短、根系变硬变脆、根径增加、根冠变大;100 mg·L^-1浓度的Cu₂O-NPs处理下,小麦根尖有丝分裂指数显著降低,根尖细胞形状不规则化、质壁分离、细胞出现空泡化、细胞核核膜模糊、核内染色体异常。在水培条件下,Cu₂O-NPs对小麦幼苗具有一定的遗传学毒性效应,从而影响小麦幼苗的生长发育和根系形态结构。     

A role for the miR396/GRF network in specification of organ type during flower development,as supported by ectopic expression of Populus trichocarpa miR396c in transgenic tobacco

The MIR396 family, composed of ath‐miR396a and ath‐miR396b in Arabidopsis, is conserved among plant species and is known to target the Growth‐Regulating Factor (GRF) gene family. ath‐miR396 overexpressors or grf mutants are characterised by small and narrow leaves and show embryogenic defects such as cotyledon fusion. Heterologous expression of ath‐miR396a has been reported in tobacco and resulted in reduction of the expression of three NtGRF genes. In this study, the precursor of the Populus trichocarpa ptc‐miR396c, with a mature sequence identical to ath‐miR396b, was expressed under control of the CaMV35S promoter in tobacco. Typical phenotypes of GRF down‐regulation were observed, including cotyledon fusion and lack of shoot apical meristem (SAM). At later stage of growth, transgenic plants had delayed development and altered specification of organ type during flower development. The third and fourth whorls of floral organs were modified into stigmatoid anthers and fasciated carpels, respectively. Several NtGRF genes containing a miR396 binding site were found to be down‐regulated, and the cleavage of their corresponding mRNA at the miR396 binding site was confirmed for two of them using RACE‐PCR analysis. The data obtained agree with the functional conservation of the miR396 family in plants and suggest a role for the miR396/GRF network in determination of floral organ specification.     

The acceptability of meadow plants to the slug Deroceras reticulatum and implications for grassland restoration

Background and Aims

Despite the selective pressure slugs may exert on seedling recruitment there is a lack of information in this context within grassland restoration studies. Selective grazing is influenced by interspecific differences in acceptability. As part of a larger study of how slug–seedling interactions may influence upland hay meadow restoration, an assessment of relative acceptability is made for seedlings of meadow plants to the slug, Deroceras reticulatum.

Methods

Slug feeding damage to seedling monocultures of 23 meadow species and Brassica napus was assessed in microcosms over 14 d. The severity and rate of damage incurred by each plant species was analysed with a generalized additive mixed model. Plant species were then ranked for their relative acceptability.

Key Results

Interspecific variation in relative acceptability suggested seedlings of meadow species form a hierarchy of acceptability to D. reticulatum. The four most acceptable species were Achillea millefolium and the grasses Holcus lanatus, Poa trivialis and Festuca rubra. Trifolium pratense was acceptable to D. reticulatum and was the second highest ranking forb species. The most unacceptable species were mainly forbs associated with the target grassland, and included Geranium sylvaticum, Rumex acetosa, Leontodon hispidus and the grass Anthoxanthum odoratum. A strong positive correlation was found for mean cumulative feeding damage and cumulative seedling mortality at day 14.

Conclusions

Highly unacceptable species to D. reticulatum are unlikely to be selectively grazed by slugs during the seedling recruitment phase, and were predominantly target restoration species. Seedlings of highly acceptable species may be less likely to survive slug herbivory and contribute to seedling recruitment at restoration sites. Selective slug herbivory, influenced by acceptability, may influence community-level processes if seedling recruitment and establishment of key functional species, such as T. pratense is reduced.     

‘金州报春’兜兰的非共生萌发与快速繁殖

收集授粉后不同时期报春兜兰栽培品种‘金州报春’的种子,观察种子形态特征和萌发过程,建立了高效快繁体系。试验结果表明种子萌发的最佳培养基RE＋O-3nag·L～NAA＋0．1mg·L～6-BA＋100mL·L-1椰子乳（体积比）;授粉162d后的种子萌发率较高并且无白化现象,授粉203d的种子播种后萌发率可达94-33％;分化后的原球茎在壮苗培养基上培养4个月后可得到有5～6片叶、高3～5cm的健壮试管苗。     

桂西南早熟荔枝实生资源遗传多样性的ISSR分析

利用ISSR标记技术对83份早熟荔枝(品种)单株遗传多样性进行分析。筛选出多态性高的10条IS-SR引物,共扩增出128条DNA条带,其中多态性带107条,多态性百分率为83.59%,表明桂西南早熟荔枝实生资源遗传多样性较丰富;用NTSYS软件计算出这83份材料的DICE相似系数在0.64～0.95之间,遗传亲缘关系较近;用UPGMA方法构建分子树状图,在相似系数0.75时,可将栽培品种与桂西南早熟实生单株区分开。各地区资源混杂聚类在一起,不能按地区单独聚类。     

马铃薯实生群体遗传多样性的SSR分析

以云南马铃薯品种‘剑川红’植株1个浆果中的天然实生种子产生的70个单株以及B20[CIP010(♀)×CIP004(♂)]杂交组合后代100个实生苗单株为材料,采用12对SSR引物对自交种和杂交实生群体的遗传差异性进行分析,旨在从后代群体中找到与母本(亲本)在分子水平上表现一致的植株,为种质资源的长期保存提供依据。结果表明:(1)‘剑川红’自交群体的多态性比率为81.6%,比杂交组合B20实生群体的多态性比率72.8%略高,说明2个群体的多态性比率均较高。(2)聚类分析结果显示,自交后代和杂交后代群体的遗传相似系数均较高,变化范围均在0.74~0.96之间,说明2个群体均发生了不同程度的遗传分离,但分离的程度较小,绝大多数条带表现一致。(3)在所有供试材料中,同一浆果中均未发现与‘剑川红’母株在分子水平上表现完全一致的单株。研究认为,在分子水平上寻找完全不分离的实生群体难度非常大,需进一步评价与母株(亲本)在分子水平上相似株系的田间表现,从而确定是否可以通过相近或极相近株系来恢复种源。     

不同苗龄沙地柏抗旱生理特性比较研究

以相同来源的1、3、5年生沙地柏幼苗为材料,采用室内生长池人工控水模拟不同干旱胁迫条件,对10个抗旱相关生理指标进行考察,探讨沙地柏苗龄对其抗旱特性影响。结果表明:（1）沙地柏叶片的保水力、细胞膜透性、RuBP羧化酶活性在胁迫前不同苗龄间差异显著,而叶片相对水分亏缺、气孔导度等指标不同龄苗间差异不显著。（2）在干旱胁迫条件下,随土壤含水量的降低,不同苗龄沙地柏的叶片水分亏缺、气孔导度差异一直不显著,而其净光合速率、蒸腾速率、水分利用率、胞间CO₂浓度在6.78%土壤水分含量时出现显著差异;当土壤水分含量降低到4.52%时,不同苗龄的叶片光量子效率也出现显著差异。（3）各苗龄组随着干旱胁迫的加剧,5年生沙地柏净光合速率、RuBP羧化酶活性、光量子效率显著低于1年生沙地柏,而其胞间CO₂浓度显著高于1、3年生沙地柏,并且其气孔导度、蒸腾速率随土壤水分含量降低而下降的幅度最大,水分利用率增加幅度比1、3年生的更多。研究表明,不同苗龄沙地柏幼苗抗旱性指标对干旱胁迫的响应程度存在差异,抗旱指标对苗龄的稳定性不同;干旱胁迫条件下低苗龄沙地柏比高苗龄的生长势更强,更有生命活力,但高苗龄沙地柏对水分胁迫的适应能力强于低苗龄;另外,在进行抗旱鉴定时,试验苗木年龄最好一致,抗旱鉴定指标选取也需考虑其对材料年龄的敏感性及稳定性。     

水淹对枫杨幼苗光合生理特征的影响

通过设置对照(CK)、连续性水淹(CF)和间歇性水淹(PF)3个水分处理,模拟三峡库区库岸带土壤水分变化,研究乡土树种枫杨当年实生幼苗的生理生态适应机制.结果表明: 不同水分处理均显著影响枫杨幼苗的光合作用、生物量积累和生长.与CK相比,CF和PF组枫杨幼苗除胞间CO₂浓度升高,净光合速率(P_n)、气孔导度(g_s)均显著降低.其变化趋势是枫杨幼苗的P_n、g_s在试验初期下降,然后逐渐恢复或趋于稳定.随着处理时间的延长,CF和PF组枫杨幼苗的总生物量、根生物量、茎生物量、叶生物量、株高和地径均呈现上升趋势.CF和PF组的总生物量、根生物量、叶生物量和株高,以及PF组的茎生物量均显著低于CK,而CF组的茎生物量与CK无显著差异,其地径还高于CK.枫杨幼苗具有耐受水湿而不耐水淹-干旱交替的生理生态特征.     

模拟酸雨对不同类型玉米种子萌发和幼苗生长的影响

以普通玉米、糯玉米、爆裂玉米和甜玉米为材料,研究了不同模拟酸雨(pH 6.0、5.0、4.0、3.0、2.0、1.0)对玉米种子萌发和幼苗生长的影响.结果表明:pH 2.0 ～5.0模拟酸雨对玉米种子萌发和幼苗生长没有显著影响;pH l.0处理的普通玉米、糯玉米、爆裂玉米和甜玉米的种子发芽率分别为91.3％、68.7％、27.5％和11.7％.与pH 6.0处理(CK)相比,pH l.0模拟酸雨显著降低了玉米种子的发芽率、发芽指数、活力指数、发芽速度、苗高、根长、苗和根干物质、贮藏物质运转效率,延长了平均发芽时间.pH l.0模拟酸雨对玉米幼苗生长阶段的影响大于发芽阶段,对幼苗地下部分的影响大于地上部分;受基因型的影响,普通玉米和糯玉米的抗酸雨能力最强,其次为爆裂玉米,甜玉米最差.玉米属于抗酸雨作物,酸雨抑制阈值介于pH1.0～2.0之间.酸雨地区可优先选择种植普通玉米和糯玉米.