Morphological traits and physiological characteristics in drought tolerance in 20 shrub species on the Qinghai-Xizang Plateau

Aims Providing indispensably theoretical evidence for establishing indices of evaluation on drought tolerance in shrubs, and screening for tree species that are drought tolerant for afforestation in arid regions or for matching their characteristics with suitable habitat conditions are the key to vegetation restoration in the Qinghai-Xizang Plateau. However, these issues are not adequately addressed in recent research due to lack of systematic methods. Therefore, our objective was to make a comprehensive evaluation on drought tolerance in 20 shrub species collected from different areas in Qinghai-Xizang Plateau, and to study their underlying mechanisms in drought tolerance.
Methods We made measurements on variables depicting root characteristics, including the root length (TRL), surface area (TRSA), volume (TRV), and tips number (TRTN) of all roots, the root length (FRL), surface area (FRSA), volume (FRV), and tips number (FRTN) of fine roots (d≤2 mm), and derived plant characteristic indices including thickness of cuticle (CT), thickness of palisade tissue (TPT), thickness of spongy tissue (TST), TPT/TST, thickness of leaf (LT), palisable tissue cell density, and tissue structural tense ratio (CTR = TPT/LT × 100%) and spongy tissue loosened ratio (SR = TST/LT × 100%) of leaf anatomical structure, root to shoot ratio (RSR), leaf transpiration rate (T_r), instantaneous water use efficiency (WUE_i), and carbon isotopic composition (δ¹³C) of the 20 shrub species through field experiments. Correlation analysis and principal component analysis were performed on the 19 variables and indices.
Important findings Different shrubs had different mechanisms of drought tolerance. In this study, the character- istics of drought tolerance were mainly categorized into 6 types, involving modifications of (1) root systems, (2) leaf anatomical structure, (3) leaf pattern, and (4) biomass allocation, or via (5) low water-consumption and (6) high WUE_i. Different genera or different tree species within the same genus clearly differed in drought tolerance. The species of the genus Hippophae were relatively poorly tolerant to drought, whereas several shrubs including Potentilla fruticosa, Berberis julianae, Caragana arborescens, Spiraea salicifolia and Hippophae rhamnoides ssp. mongolica occurred to be more drought tolerant than other shrub species investigated in this study. On the other hand, there were highly significant correlations among the characteristics of root systems and among characteristics of leaf anatomical structure. The results of principal component analysis on 19 variables and indices showed that TRL, TRSA, TRV, TRTN, FRL, FRSA, FRV, FRTN, CT, TPT, TST and WUE_i could be effective indicators of drought tolerance of shrubs in the Qinghai-Xizang Plateau. In addition, the drought tolerance of shrubs had a close connection with their origin of collections; the shrubs collected from Xining prefecture in Qinghai Province were more drought tolerant than those from Tianshui Prefecture in Gansu and Lasa Prefecture in Xizang.     

毛乌素沙地中间锦鸡儿整株丛的蒸腾特征

中间锦鸡儿(Caragana intermedia)是一种优良的防风固沙灌木。有关其蒸腾作用的测定研究多是通过对单叶或小枝蒸腾速率的测定值推算整株丛的蒸腾耗水。该研究选择在中间锦鸡儿株丛的主根安装“热扩散探针”来测定整株丛的蒸腾耗水。结果表明: 中间锦鸡儿整株丛液流量的日变化可划分为4个阶段: 1)液流量迅速上升阶段(8:00~11:30), 其液流量占全天液流量的21.21%; 2)液流量最高而相对稳定阶段(12:00~18:00), 液流量占全天液流量的58.84%; 3)液流量迅速降低阶段(18:30~21:00), 液流量占全天液流量的10.62%; 4)液流量最低而稳定阶段(21:30~次日8:00), 液流量占全天液流量的9.32%。从所观测的中间锦鸡儿整株丛液流量的日变化可以看出: 在午间(12:00~14:00), 中间锦鸡儿整株丛蒸腾虽因环境因子的影响(如云朵遮阴)会发生较小的波动, 但并没有出现明显的“午休”现象, 而是保持相对稳定的高蒸腾速率。环境因子对中间锦鸡儿整株丛液流量影响的强弱次序依次为: 太阳辐射>空气温度>水蒸气压亏缺>空气相对湿度>土壤温度>风速。液流量对环境因子变化的响应存在着明显的时滞现象。根据所测大、中、小3个中间锦鸡儿整株丛树干液流量数据, 计算出一个中等大小(株高为110 cm, 冠幅为0.6 m², 叶片总干重为51.82 g)的中间锦鸡儿整株丛在测定时间内的日蒸腾耗水量为2.2 kg · d^-1。     

一只长江江豚妊娠期昼间行为及其时间分配

长江江豚(Neophocaena phocaenoides asiaeorientalis Pilleri and Gihr,1972)属于哺乳纲(Mammalia)、鲸目(Cetacea),是仅分布于长江中下游及其附属湖泊中的惟一且相对独立的一个江豚淡水亚种(高安利和周开亚,1995),也是中国水域中三个江豚种群中最为濒危的一个亚种,<中国濒危动物红皮书·兽类>也将其列为濒危级(汪松,1998).     

东亚飞蝗中肠几丁质酶基因的克隆、序列分析及组织定位

通过RACE方法,克隆了东亚飞蝗Locusta migratoria manilensis (Meyen)几丁质酶基因 (LmChi)cDNA全序列 (GenBank 登录号：EF092841)。获得的cDNA全长1 604 bp,其中可读框1 452 bp, 编码483个氨基酸。推测其氨基酸序列与18家族昆虫几丁质酶有较高的相似性。与其他几丁质酶一样,东亚飞蝗几丁质酶序列也包含一个信号肽、一个几丁质酶活性位点、一个碳端丝氨酸富集区和一个几丁质结合域。半定量RT-PCR研究表明,LmChi基因只在东亚飞蝗不同发育阶段的中肠组织中表达,而在东亚飞蝗体壁、前肠和后肠均没有发现LmChi基因的转录。     

大型海藻龙须菜浸出组分对中肋骨条藻的化感抑制作用

研究了龙须菜乙醇浸出组分对中肋骨条藻的化感抑制作用。结果显示,浸出组分对中肋骨条藻产生明显抑制作用,且微藻的生物量迅速减少。当龙须菜浸出成分浓度为42mg·L^-1时,相对抑制率为50%,即半效应浓度(EC₅₀)。龙须菜对赤潮藻产生明显的化感抑制作用,延缓了富营养化水体中赤潮藻的爆发,从而使龙须菜具有控制中肋骨条藻赤潮发生的潜在价值。     

东北山地灌木沼泽植物铜、锌分布特征及季节动态

研究了东北山地灌木沼泽主要植物--细叶沼柳、五蕊柳、丛苔草和修氏苔草中Cu、Zn分布、积累及其季节动态.结果表明:Cu含量变动范围为6～12 mg·kg-1,细叶沼柳和五蕊柳各器官Cu含量为根》枝》叶;丛苔草和修氏苔草为茎》叶》根,Cu主要积累在灌木的根系和苔草的茎叶中,灌木和苔草中Cu含量相差较小.Zn含量变动在30～250 mg·kg-1之间,细叶沼柳和五蕊柳各器官Zn含量为叶》枝》根,尤其是叶和枝中都在150 mg·kg-1以上;丛苔草和修氏苔草各器官Zn含量为根》茎》叶.Zn多积累在灌木的叶和苔草的根中,且灌木各器官Zn含量明显高于苔草.细叶沼柳和五蕊柳各器官对Zn的富集系数均大于1.45,显示出较强的Zn富集能力.4种供试植物在生长初期地上部分Cu、Zn含量较高,且随着季节变化呈波动式降低趋势,而根中则表现出生长初期和末期Cu、Zn含量较高的特点.     

不同寄主植物对云南紫胶虫自然种群的影响

研究了云南紫胶虫(Kerria yunnanensis)在聚果榕、南岭黄檀、钝叶黄檀和偏叶榕上的发育、存活和繁殖情况.结果表明：在自然条件下,云南紫胶虫在钝叶黄檀上的种群初始密度最高,为181.17头·cm^-2,聚果榕上最低,为145.27头·cm^-2;雄虫占的比例以在南岭黄檀上最少,为0.19,偏叶榕和聚果榕上最多,为0.24;从幼虫到成虫的累积死亡率,南岭黄檀上最高,为90.03%,偏叶榕上最低,为87.05%;完成世代时间以在南岭黄檀上最长,为156 d,聚果榕上最短,为140 d;平均怀卵量以在南岭黄檀上最高,为536粒,聚果榕上最低,为345.86粒;虫体质量以在南岭黄檀上最大,为12.62 mg,偏叶榕上最小,为9.03 mg;世代净增值率以在南岭黄檀上最高,为48.51,聚果榕上最小,为32.79.综合比较4种不同寄主植物,南岭黄檀是云南紫胶虫夏季世代种群生长发育和繁殖最适宜的寄主.     

凉山半细毛羊1号染色体微卫星遗传连锁图谱的构建

实验选择绵羊1号条染色体上的9个微卫星标记,采用父系半同胞家系群体（共387个个体）构建凉山半细毛羊1号染色体遗传连锁图。建立的资源参考家系通过20个微卫星标记进行了系谱确证。试验结果表明,9个标记的等位基因数变化范围为5~15个,杂合度在0.202~0.831之间,平均杂合度为0.617,各标记的平均多态信息含量PIC=0.604。构建的凉山半细毛羊1号条染色体遗传连锁图总长度311.0 cM,与美国肉畜中心（USDA）和国际绵羊作图中心（IMF）构建的绵羊1号条染色遗传连锁图结果基本一致。可用于下一步的QTL定位研究。     

保安湖—湖湾大型水生植物群落格局的研究

用地质统计学中的半方差和双对数半方差图对保安湖-湖湾(黄风口)的大型水生植物群落格局进行了研究,在不同的尺度上对群落及其主要组成种类的空间异质性进行了定量的描述。结果表明:保安湖黄风口大型水生植物群落的双对数半方差图存在线性区域,群落具有分形特征(自相似性).在不同的尺度下,群落和各组成种类空间格局具有不同的分形维数值,异质性程度存在差异。但其异质性程度不高,建议进行群落调查时,样方尺度应取520m;单一种群调查时的样方尺度取380m.       

S-苯基-L-半胱氨酸测定方法的研究

建立了用旋光度法和紫外分光光度法分析测定S 苯基 L 半胱氨酸的方法。研究表明 ,旋光度法适用于提纯后的产品中S 苯基 L 半胱氨酸含量的测定 ,而紫外分光光度法适用于初始产品中S 苯基 L 半胱氨酸含量的测定