卷叶锦鸡儿——锦鸡儿属(豆科)一新种

报道了产于蒙古、内蒙古、宁夏和甘肃的锦鸡儿属(豆科)一新种--卷叶锦鸡儿。该种因叶轴全部宿存,荚果里外均被毛,植株垫状而与Caragana tibetica Kom.相近,但因小叶内卷,管状,横切面呈"O"形,翼瓣耳圆钝而不同。     

Interspecific relationships of Caragana microphylla,C. davazamcii and C. korshinskii (Leguminosae) based on ITS and trnL-F data sets

The taxonomic treatment of Caragana davazamcii Sancz. has been a controversial matter, as its relationship with C. microphylla Lam. and C. korshinskii Kom. is not clear. It was treated as an independent species, or a variety under C. microphylla or C. korshinskii. This study is to examine the interspecific relationship of these three species and the origin of C. davazamcii based on internal transcribed spacer (ITS) and non-coding region of chloroplast trnL-F, combined with morphological data and geographical distribution. The trnL-F sequence of C. davazamcii is identical to that of C. microphylla but differs distinctly from that of C. korshinskii. The high congruence of ITS copies through both direct and cloning sequencing rejects the recent hybridization hypothesis of C. davazamcii between C. microphylla and C. korshinskii. In contrast, two different ITS sequence copies were found respectively in each individual of C. microphylla and C. korshinskii. One of the two ITS sequences in C. microphylla is identical to that of C. davazamcii. This result indicates that C. davazamcii might have taken part in the hybridization of C. microphylla as one parent , or that extensive gene flow might have occurred between these two species, thus resulting in the morphological similarity of them. However, the similarity of some morphological characters of C. davazamcii to those of C. korshinskii might result from the convergent adaptation to their common ecological environment.     

CO2浓度倍增和土壤干旱对两种幼龄沙生灌木碳分配的影响

利用大型环境生长箱研究了两种幼龄沙地优势灌木柠条 (Caraganaintermedia) 和羊柴 (Hedysarummon golicum) 对CO2 浓度倍增和土壤干旱交互作用的响应。CO2 浓度倍增并没有改善两种沙生灌木叶片的水分状况, 而土壤干旱使叶片的相对含水量 (RWC) 显著降低。在土壤水分充足条件下, CO2 浓度倍增促进两种沙生灌木植株生长, 在干旱条件下则主要促进根的生长, 提高根冠比。土壤干旱显著减少了植株生物量, 但相对促进了根的生长, 特别是显著提高了羊柴的根冠比。CO2 倍增使稳定性碳同位素组分 (δ13 C) 降低, 但土壤干旱使之增加。两种沙生灌木叶片与根部的δ13 C值呈极显著线性关系, 羊柴的斜率大于柠条的, 表明前者叶片与根部在光合产物分配上具有较高的生态可塑性, 这和干旱条件下羊柴的根冠比增加相关联。羊柴的“源库”调节特性反映了对土壤水分胁迫具有较高的耐性。     

不同天气条件下小叶锦鸡儿茎流及耗水特性

采用以热平衡为原理的Dynamax包裹式茎流测量系统,于2006年对科尔沁沙地人工小叶锦鸡儿群落的液流变化进行连续监测,利用实验区自动气象站同步检测光合有效辐射、气温、相对湿度和风速等气象因子,结合人工记录的天气状况,分别选取4种最典型的天气条件,分析了小叶锦鸡儿的茎流变化、单枝耗水量及其与气象因子的关系.结果表明:在高温、强辐射条件下,小叶锦鸡儿的液流呈"几"字型宽峰曲线,以低耗水的蒸腾特性耐受干旱缺水的环境.不同天气条件下,小叶锦鸡儿液流日变化波动曲线及其主要影响因子各异,但光合有效辐射始终是液流变化的主导因子.小叶锦鸡儿茎干液流通量密度的变化是各种气象因子综合作用的结果.单枝日耗水量的总体变化趋势是从晴天、阴天、风天到雨天依次减少,其平均值分别为459、310、281和193mg.d-1.     

小叶锦鸡儿基因组DNA的提取及AFLP反应体系的建立

以小叶锦鸡儿幼嫩叶片为材料,采用改良的SDS法提取其基因组DNA,通过优化AFLP技术体系中的几个主要因素,建立了适合小叶锦鸡儿的AFLP银染反应体系。改良的SDS法能通过在提取液中加入β-巯基乙醇防止氧化、加入PVP去除酚类等物质,获得满足AFLP分析要求的纯度高、完整性好的基因组DNA;用EcoRⅠ和MseⅠ37 ℃双酶切4 h后可以将500 ng的基因组DNA完全切开。酶切产物和接头经16℃连接过夜后,用带有1个选择性碱基的引物和带有3个选择性碱基的引物分别进行预扩增和选择性扩增,扩增产物经变性聚丙烯酰胺凝胶电泳分离,用AgNO₃染色,得到了清晰的指纹式样。小叶锦鸡儿AFLP反应体系的建立为利用该技术研究小叶锦鸡儿的遗传多样性奠定了实验基础。     

锦鸡儿属植物一些种类的染色体数目及核型研究

报道了国产10种锦鸡儿的染色体数目,并对其中9种的核型进行了研究。这9个种的核型公式分别为：荒漠锦鸡儿（Caragana roborovskyi）,2n＝16＝10m(2SAT)+6sm;川西锦鸡儿（C. erinacea）,2n=16=10m+6sm;密叶锦鸡儿（C. densa）,2n=16=10m（2SAT）+6sm;刺叶锦鸡儿（C. acanthophylla）,2n=16=12m+4sm;柄荚锦鸡儿（C. stipitata）,2n=16=10m+6sm;甘蒙锦鸡儿（C. opulens）,2n=16=12m(2SAT)+4sm;白皮锦鸡儿（C. leucophloea）,2n=32=22m(4SAT)＋10sm;北疆锦鸡儿（C. camilli-schneideri）,2n=32=20m(4SAT)+12sm;中亚锦鸡儿（C. tragacanthoides）,2n=32=20m(2SAT)+10sm+2st+2B。白毛锦鸡儿（C.licentiana）2个居群的染色体数目均为2n=32,为四倍体。研究结果表明,锦鸡儿属的核型一般比较对称,核型上的特化往往与其形态上的特化相关联,但也有例外。从倍性水平上来看,二倍体类群多是一些羽状叶的种,在分布上倾向于亚洲东部其祖先分布区,而四倍体的种类多是一些假掌状叶的类群,分布于西部干旱生境中,在形态上也表现的较为特化。这也符合锦鸡儿属的演化趋势。     

柠条锦鸡儿肉桂酰辅酶A还原酶基因克隆和分析

肉桂酰辅酶A还原酶(cinnamoyl-CoA reductase,CCR)是木质素特异合成途径中的关键酶。根据已报道的植物CCR基因序列设计简并引物,利用RACE技术,首次从柠条锦鸡儿(Caragana korshinkii Kom.)中克隆得到CCR基因全长cDNA序列,命名为CkCCR,GenBank登录号为HQ829859。该序列长1 270bp,具备长度为1 014bp的完整开放阅读框(ORF)。推导该基因编码的蛋白质有434个氨基酸,预测等电点6.69,分子量36.76kDa。序列分析发现,柠条锦鸡儿CCR基因推导的氨基酸序列与其它植物来源的CCR序列高度相似,并且具有植物CCR共有的氨基酸序列"KNWYCYGKA"以及NADPH的结合序列。系统进化分析显示,柠条锦鸡儿CCR与拟南芥CCR2处于同一分支,与同属豆科的银合欢CCR亲缘关系最近。利用荧光定量PCR技术对柠条锦鸡儿一个月龄幼苗基因转录水平进行检测,结果显示CkCCR基因在根、茎、叶中广泛表达,并且干旱处理初期表达量有所下降,处理后期又恢复到未处理时的表达水平。     

Photosynthetic and morphological characters of Caragana microphylla in different slope aspects and positions

In order to find out how small scale topographical factors affect growth and physiological characters of Caragana microphylla, which is a widely distributed shrub species and has an important role in restoring degraded grassland in natural ecosystem, a natural population of C. microphylla was chosen in a typical steppe community in June, 2009. The population was 34 km to the southeast of Xilinhot City, China, and a total of 54 shrubs were selected from different slope aspects and positions. We investigated the photosynthetic and morphological characters of these shrubs and analyzed the relationship between plant traits of C. microphylla and soil nitrogen and phosphorus availability. Moreover, the relationship between plant traits of C. microphylla and herbaceous aboveground biomass was studied. (1) The maximum net photosynthetic rate (Pn_max) was significantly lower on shady slopes than that on sunny slopes and higher on upper slopes than that on lower slopes. Stomatal conductance (Gs), net photosynthetic rate/intercellular CO₂ concentration (Pn/Ci) and intercellular CO₂ concentration (Ci) under saturated irradiance showed similar trends with slope aspect and position. Likewise, the maximum photochemical efficiency of PSII (Fv/Fm), PSII potential activity (Fv/Fo) and the first-year shoot morphological characters of C. microphylla were also correlated with slope aspect and position. (2) Soil nitrogen availability showed no significant effect on photosynthetic or morphological traits of C. microphylla, however, there were several significant relationships between soil phosphorus availability and plant traits. Dry weight, shoot length, compound leaf size, and leaflet length of first-year shoots of C. microphylla were significantly negatively correlated with soil C:P ratio. Though not significant, photosynthetic parameters under saturated light and other morphological characters of first-year shoots were negatively correlated with soil C:P ratio, i.e., these traits increased with increasing soil phosphorus availability. These suggested that the difference of soil phosphorus availability played an important role in making C. microphylla having different photosynthetic and morphological characters on different slope aspects and positions. The individuals grown in relatively P-rich site had longer shoots and larger leaves and grew better. Low phosphorus content was thought to limit photosynthetic activity through several different mechanisms, including both stomatal and non-stomatal limitations, the latter being more likely in the present study. (3) Photosynthetic and morphological characters of C. microphylla were all negatively correlated with herbaceous aboveground biomass, though only Pn/Ci and length of first-year shoot were significantly correlated with it. This indicated that the difference in plant community was a factor making C. microphylla have different growth and physiological characters on different aspects and positions of slope. A number of studies showed that grazing of the herbaceous layer promoted the establishment and proliferation of woody species, and then led to grassland deterioration; but in arid and semi-arid ecosystems, some widely distributed shrub species like C. microphylla created resource islands and provide favorable microhabitat for grass species. In the present study, we found negative correlations between traits of C. microphylla and herbaceous aboveground biomass. We suggested that the removal of livestock grazing result in the decrease of the distribution C. microphylla and increase of grass coverage, and lead to the restoration of the typical steppe.     

科尔沁沙地植被生产力对模拟增加降水和氮沉降的响应

采用随机区组设计,利用降水收集装置和地表施氮处理,模拟降水和氮沉降增加对科尔沁沙地典型小叶锦鸡儿群落植被生产力的影响.结果表明:降水量增加1/7,植被平均高度增加不明显,植被生物量增加了17.6%;降水量增加2/7,植被平均高度增加了23%,植被生物量增加了31.8%;模拟氮沉降处理的一年处理结果对植被生物量增加不明显;降水是影响沙地植被生产力的关键因素,植被生产力对降水量增加响应迅速,短期的氮沉降对植被生产力的影响不显著.     

科尔沁沙地4种植物抗旱性的比较研究

对科尔沁沙地小叶锦鸡儿,紫穗槐,差巴嘎蒿和胡枝子4种植物的若干水分生理生态指标进行了测定。结果表明,小叶锦鸡儿具有低水势,高水力和束缚水／自由水比及水分利用效率,抗旱性强;紫穗槐的各项指标与小叶锦鸡儿相反,抗旱性最差;差巴嘎蒿虽然水势较高,但它的持水力高,束缚水／自由水比和水分利用效率都较高,抗旱性也较强,但次于小叶锦鸡儿;胡枝子的水势和持水力较低,束缚水／自由水比及水分利用效率一般,它的抗旱性强于紫穗槐,但比差巴嘎蒿差。