从形态学看北美红杉的亲本

本文通过形态性状的比较研究认为AAAABB的同源异源多倍体红杉可能由亲本水杉(属)和巨杉(属)杂交起源,它们分别为红杉提供了染色体组AA和染色体组B。这与根据核型等资料的分析结果相吻合。但跟Stebbins认为红杉除水杉(属)以外的另一个亲本已经灭绝并没有留下近缘的推论存在分歧。     

北美红杉起源的时间和地点的探讨

根据笔者认为的北美红杉的亲本可能是分别以水杉、巨杉为直接后裔或留下近缘的水杉属和巨杉属的二个古代种及Florin的古植物学资料,本文推测北美红杉这个AAAABB同源异源多倍体(autoallopolyploid)杂交起源的时间和地点有三种可能:(1)中新世的美国西部(以俄勒冈州及其附近为中心);(2)古新世的格陵兰岛西海岸;(3)晚白垩纪的美国中西部(包括怀俄明州、科罗拉多州)。其中第一个推测的可能性更大。     

杉科的细胞分类学和系统演化研究

根据杉科的核型资料,本文(1)提出“1B”可能是一个新的高等植物核型类型;(2)讨论了各属的有关分类学问题及相互亲缘关系,它们的进化顺序可能是柳杉属、水松属、落羽杉属、水杉属、巨杉属、红杉属、杉木属(密叶杉属与之近缘)、台湾杉属;(3)支持金松属分立成金松科,它可能比杉科各属原始; (4)红杉(AAAABB)的亲本可能是二个古代种“水杉”和“巨杉”,它们的直接后裔或留下的近缘是水杉和巨杉;(5)杉科存在A和L两条进化路线,前者包括柳杉属、水松属、落羽杉属、台湾杉属;后者包括水杉属、巨杉属、红杉属、杉木属(密叶杉属);(6)提出一个杉科新系统(包括一个新亚科):Ⅰ.柳杉亚科(柳杉属),Ⅱ.落羽杉亚科(水松属、落羽杉属),Ⅲ.红杉亚科(水杉属、巨杉属、红杉属),Ⅳ.杉木亚科(杉木属、密叶杉属),Ⅴ.台湾杉亚科,新亚科(台湾杉属)。本文还对前人的杉科系统作了讨论。     

杉科的细胞分类学和系统演化研究

根据杉科的核型资料,本文(1)提出“1B”可能是一个新的高等植物核型类型;(2)讨论了各属的有关分类学问题及相互亲缘关系,它们的进化顺序可能是柳杉属、水松属、落羽杉属、水杉属、巨杉属、红杉属、杉木属(密叶杉属与之近缘)、台湾杉属;(3)支持金松属分立成金松科,它可能比杉科各属原始;(4)红杉(AAAABB)的亲本可能是二个古代种水杉”和“巨杉”,它们的直接后裔或留下的近缘是水杉和巨杉;(5)杉科存在A和L两条进化路线,前者包括柳杉属、水松属、落羽杉属、台湾杉属,后者包括水杉属、巨杉属、红杉属、杉木属(密叶杉属);(6)提出一个杉科新系统(包括一个新亚科)：I．柳杉亚科(柳杉属),II．落羽杉亚科(水松属、落羽杉属),III．红杉亚科(冰杉属、巨杉属、红杉属),Ⅳ.杉木亚科(杉木属、密叶杉属),V．台湾杉亚科,新亚科(台湾杉属)。本文还对前人的杉科系统作了讨论。     

北美红杉的一个亲本是灭绝的吗?

本文作者对Stebbins的"水杉和红杉的染色体及亲缘关系"一文进行了评述, 认为红杉除水杉(属)以外的另一个二倍体亲本可能并没有灭绝, 它或许就是巨杉(属).     

巨杉可能是红杉的一个祖先吗?

世界闻名的珍稀植物红杉Sequoia sempervirens是裸子植物中唯一染色体倍性最高的自然多倍体(2n=6x=66),植物学工作者一直十分关注着它的起源问题。Hirayoshi &Nakamura认为巨杉Sequoiadendron giganteum可能为红杉提供了一个染色体组,但Stebbins在假设一个古代水杉属Metasequoia植物可能是同源异源多倍体(autoallopoly-     

水杉是北美红杉的一个亲本吗？

本文根据有关细胞学和形态学资料.不同意Schlarbaum等以红杉没有水杉的具长着丝点区域的标记染色体来否定水杉(属)是红杉的亲本,同时认为,他们提出某种杉木属植物为红杉提供了染色体组而是它的亲本的意见难以成立,从而支持Stebbins的假设,水杉(属)可能是北美红杉的一个亲本。而且,它或许还是一个父本。     

从杉木看一个新的高等植物核型类型

本文报道浙江丽水地区栽培杉木的核型为K(2n)=2x=22=20m(2SAT)+2sm,它的染色体长度比(最长/最短)大于2、小于4,没有臂比大于2的染色体,属Stebbins的“1B”核型。根据Stebbins的研究,后者在高等植物中尚未发现过,因此“1B”可能是一个新的高等植物核型类型。笔者还发现其他产地的杉木及德昌杉木、米德杉木、巨杉和红杉—B染色体组的核型也为“1B”类型。     

生境的破坏或改变对杉科种属分布的影响

杉科共有10个属16种,其中5个是单种属(水杉属、水松属、巨杉属、北美红杉属、金松属),5个是寡种属(杉木属、台湾杉属、柳杉属、落羽杉属、密叶杉属),两者各占50%。分布于北温带地区,多在东亚和北美洲,仅密叶杉属分布于南半球澳大利亚的塔斯马尼亚。植物与生境是一个互相依存的统一体,而生境的破坏或改变对杉科植物种属分布有严重的影响。在美国加利福尼亚洲现今仅有巨杉和北美红杉两个单种属,这是由于火山爆发留下来,现在仅分布于美国加州部分地区。     

杉科植物的系统发育分析

本文以形态学为依据,参考其他学科的研究成果,用分支分类方法并结合表征分类方法探讨了杉科植物的系统演化关系,提出了新的分类系统。在分支分类中,金松科被选作外类群。主要根据外类群比较原则、化石原则和一般的演化规律,确定了性状的祖征和衍征,采用最大同步法、综合分析法、演化极端结合法及最小平行进化法共四种方法进行分支分析,选择最简约的分支图作为本文讨论基础。在表征分类中,选取59个性状,利用距离系数和类平均法,对金松属和杉科各属进行了聚类运算,得出表征图。综合两种分析结果,主要结论如下:(1)属间关系:柳杉属是现存杉科植物中最原始的类群。水松属和落羽杉属关系密切,二者与柳杉属近缘。巨杉属和北美红杉属关系密切,是中级进化水平的类群。水杉属与巨杉属和北美红杉属的亲缘关系相对较近。杉木属、密叶杉属和台湾杉属关系密切,是杉科植物中的高级进化类群,其中又以台湾杉属演化水平最高。(2)系统排列:支持金松科的成立,将杉科分成5族,即柳杉族(仅含柳杉属)、落羽杉族(含水松属、落羽杉属)、北美红杉族(含巨杉属、北美红杉属)、水杉族(仅含水杉属)和杉木族(含杉木属、密叶杉属及台湾杉属)。     

水杉的核型研究

本文观察了水杉的染色体,确定2n=22,核型公式为K(2n)=22m(2SAT),全具中着丝点,有一对随体。第8、10、11号染色体具“长着丝点区域”。属“1A”型,与北美红杉-AA的核型非常相近,可能是它的一个亲本种的直接后裔。     

水杉属和红杉属化石叶表皮鉴定参照系的特殊性

杉科植物的许多属种在小枝的形态和叶片排列上相似,而杉科植物的化石标本多保存为枝叶形式。表皮的特征作为压型化石枝叶标本细胞信息的重要来源,甚至是惟一来源。一直作为杉科植物化石分类鉴定的主要依据。水杉和北美红杉分别是水杉属和红杉属植物化石的惟一现存最近亲缘种,以往关于北美红杉的气孔分布和排列等方面的报道存在分歧,根据作者的研究,北美红杉的表皮特征变异幅度非常广。水杉的气孔分布也与以往报道有差异。利用表皮的特征鉴定杉科植物化石时;不同的处理方法和处理时间,角质层的完整程度和观察数量等均可以影响植物表皮特征的正确获取。     

Variation of cuticle micromorphology of Metasequoia glyptostroboides (Taxodiaceae)

Leaf cuticle micromorphology of Metasequoia glyptostroboides Hu & W. C. Cheng was studied with SEM using samples collected from its natural population in south-central China and cultivated trees in Nanjing City. The cuticle characters from both natural and cultivated trees living in different environments allowed us to re-evaluate taxonomic values of certain cuticular characters and to assess their relationships with environmental factors and the degree of tree maturity. External and internal cuticular features of both adaxial (upper) and abaxial (lower) leaf surfaces revealed the following: (1) Cuticle micromorphology of M. glyptostroboides is distinct among Taxodiaceae, but that variation does not exceed the range of this family. (2) Except for an isolated tree outside the Metasequoia valley, the cuticular features displayed by individual trees from the main Metasequoia groves demonstrate a high degree of uniformity, which is in congruence with previous observations on the low population variability at the gross morphology level. (3) Cuticular characters of grafted Metasequoia trees living in different environments are identical to those of their original trees, indicating that no cuticular character of this species could be regarded as an environmental indicator. (4) Recognition of some unique cuticular features in a Metasequoia tree in an isolated location may lead to a rare source for increasing the variation of this endangered species.     

水杉栽培居群的遗传多样性研究

利用RAPD技术,对9个水杉(Metasequoiaglyptostroboides)栽培居群的遗传多样性进行了初步研究。用10bp的随机引物16条,共扩增出103个位点,其中37个为多态位点,占35.92%。各居群的多态位点百分率在16.50%~33.01%之间。POPGENEversion1.31软件处理结果如下:居群的Shannon’s信息指数为0.1930。遗传距离在0.0130~0.0650之间,遗传一致度在0.9370~0.9871之间。AMOVA分析结果显示遗传变异主要存在于居群内,占89.05%,居群之间有一定的分化。上述结果表明水杉栽培居群的遗传多样性略低于自然居群,涵盖了自然居群近80%的遗传多样性。由此可以确认栽培水杉的种源是经过混合的,它们在相当程度上代表了自然居群的遗传多样性水平。采自潜江的9株丛枝水杉(Metasequoiaglyptostroboidesvar.caespitosa)没有扩增出特有位点,将其视为一个居群根据遗传一致度作UPGMA聚类分析时,该居群和湖北的3个居群及南京(NJ)、成都(CD)居群聚在一起;单株聚类时丛枝水杉也没有聚成独立的一支,而是比较分散,因此不支持将丛枝水杉作为水杉的一个变种的分类处理。从亲缘关系上看,丛枝水杉应当归属于湖北潜江蚌湖种子园(BH)和湖北潜江广华(GH)居群,这与其分布现状也是吻合的。     

水松的细胞学研究

本文报道了水松的核型公式K(2n)=22=22m,为“1A”类型。染色体相对长度组成为2n=22=2L+4M_2+16M_1。8号染色体具长着丝点区域,这是核型的一个特征。与近缘的国产种柳杉和水杉相比较。三者由原始到进化的顺序可能为(柳杉、水松)、水杉,水松与柳杉最接近,水杉和水松较近缘。本文还计算了水松的染色体体积。     

Phylogenetic Analysis of the Family Taxodiaceae

In the present paper,both cladistic analysis and phenetic analysis were conducted to evaluate the phylogenetic relationships of the Taxodiaceae based on an extensive literature review and study of herbarium． In the cladistic analysis,the Sciadopityaceae was chosen as outgroup．The polarity of characters was determined mainly according to outgroup comparison,fossil evidence and generally accepted viewpoints of morphological evolution．By the result of compatibility analysis,character 2(leaf type),which possessed a much higher coefficient than others whether or not its polarity was altered,was deleted． Finally,a data matrix consisting of all the extant nine genera and 24 characters was analyzed using Maximal Same Step Method,Synthetic Method,Evolutionary Extremal Aggregation Method and Minimal Parallel Evolutionary Method,and four cladograms were generated,of which only the most parsimonious one (Fig．1)was presented for discussion. The cladogram shows that the Taxodiaceae are assorted along five lines of evolution： 1)Metasequoia;2)Sequoiadendron,Sequoia;3)Cryptomeria;4)Glyptostrobus and Taxodium;5)Cunninghamia,Athrotaxis and Taiwania． Ten genera(including Sciadopitys)and 59 characters were used in the phenetic analysis．The phenogram(Fig．2)indicates that Sciadopitys is a very distinct group with remote affinity to the other genera,and the Taxodiaceae are divided into four groups：1)Sequoia,Sequoiadendron;2)Athrotaxis,Cunninghamia and Taiwania;3)Cryptomeria,Glyptostrobus and Taxodium;4)Metasequoia． Based primarily on the result of cladistics,with reference to that of phenetics,the main conclusions were drawn as follows：(1)Generic relationships：Cryptomeria should be considered the most primitive genus in the extant groups of the Taxodiaceae. Glyptostrobus and Taxodium, close to Cryptomeria, are sister taxa and relatively primitive groups. Sequoiadendron and Sequoia are closely related and intermediate advanced. Metasequoia is a more or less isolated taxon, relatively close to Sequoiadendron and Sequoia. Cunninghamia. Athrotaxis and Taiwania might represent a single lineage and form a very advanced group, of which Taiwania may be the most specialized. (2) Systematic treatments: The authors support the viewpoint that Sciadopitys should be treated as an independent family, and suggest that the Taxodiaeae should be divided into five tribes. Systematic arrangements are as follows: Taxodiaceae Warming Trib. 1. Cryptomerieae Vierhapper Gen. 5. Sequoia Endl. Gen. 1. Cryptomeria D. Don Trib. 4. Metasequoieae Pilger et Melchior Trib. 2. Taxodieae Benth. et Hook. Gen. 6. Metasequoia Miki ex Hu et Cheng Gen. 2. Glyptostrobus Endl. Trib. 5. Cunninghamieae Zucc. Gen. 3. Taxodium Rich. Gen. 7. Cunninghamia R. Br. Trib. 3. Sequoieae Wettstein Gen. 8. Athrotaxis D. Don Gen. 4. Sequoiadendron Buchholz Gen. 9. Taiwania Hayata     

Effects of tree height on branch hydraulics, leaf structure and gas exchange in California redwoods

We examined changes in branch hydraulic, leaf structure and gas exchange properties in coast redwood ( Sequoia sempervirens ) and giant sequoia ( Sequoiadendron giganteum ) trees of different sizes. Leaf-specific hydraulic conductivity ( k _L) increased with height in S. sempervirens but not in S. giganteum , while xylem cavitation resistance increased with height in both species. Despite hydraulic adjustments, leaf mass per unit area (LMA) and leaf carbon isotope ratios ( δ ¹³C) increased, and maximum mass-based stomatal conductance ( g _mass) and photosynthesis ( A _mass) decreased with height in both species. As a result, both A _mass and g _mass were negatively correlated with branch hydraulic properties in S. sempervirens and uncorrelated in S. giganteum . In addition, A _mass and g _mass were negatively correlated with LMA in both species, which we attributed to the effects of decreasing leaf internal CO₂ conductance ( g _i). Species-level differences in wood density, LMA and area-based gas exchange capacity constrained other structural and physiological properties, with S. sempervirens exhibiting increased branch water transport efficiency and S. giganteum exhibiting increased leaf-level water-use efficiency with increasing height. Our results reveal different adaptive strategies for the two redwoods that help them compensate for constraints associated with growing taller, and reflect contrasting environmental conditions each species faces in its native habitat.