中国伞形科矮泽芹属植物叶表皮形态特征的研究

利用光学显微镜、扫描电镜对伞形科矮泽芹属8种植物叶表皮形态进行观察与研究。结果表明:(1)矮泽芹属8种植物上下表皮细胞均为不规则形或规则多边形,垂周壁为近平直状或波状,上表皮细胞长宽比在1.3~2.4之间,下表皮细胞长宽比在1.5~2.5之间;在近轴面,有细叶矮泽芹、聂拉木矮泽芹和绿花矮泽芹3种植物没有气孔器的存在,其余物种气孔密度在20~74个/mm2之间,气孔指数为6.0%~17.7%;在远轴面,所有物种都具有丰富的气孔器,气孔密度为100~183个/mm2,气孔指数为16.1%~23.6%。(2)聚类分析结果显示,矮泽芹、大苞矮泽芹、粗棱矮泽芹为类群Ⅰ,鹤庆矮泽芹为类群Ⅱ,聂拉木矮泽芹、细叶矮泽芹、绿花矮泽芹为类群Ⅲ,松潘矮泽芹则单独聚为类群Ⅳ;聚类分析结果大体上支持形态学分类的结果。(3)叶表皮形态特征对于区分矮泽芹属不同物种具有十分重要的分类学价值。     

泽米科植物羽片脉序和解剖学及其系统学意义

研究了苏铁目泽米科Zamiaceae 2亚科的所有4族(Stevenson系统, 1992)共10种代表植物的羽片脉序及解剖学特征,结果显示泽米科羽片脉序为二歧分叉的平行脉,无中脉。小刺双子铁Dioon spinulosum、大头非洲铁Encephalartos friderici-guilielmii和摩尔大泽米Macrozamia moorei等的平行脉末端以不同的形式互相连接,而鳞木铁Lepidozamia peroffskyana、粗壮角果铁Ceratozamia mexicana var. robusta、竹叶角果铁C. hildae、佛州泽米Zamia　floridana、柔叶泽米Z. debilis、鳞秕泽米Z. furfuracea和短尖泽米Z. muricata等的平行脉末端不连接而直达叶缘,其中鳞木铁、粗壮角果铁和竹叶角果铁的脉达叶缘后逐渐消失。羽片的横切面结构通常由表皮、下皮厚壁细胞和叶肉组成,表皮层包括上、下表皮各一层,叶肉可能同时分化出近上表面的栅栏组织和近下表面的栅栏组织,或仅有近上表面的栅栏组织分化,或无栅栏组织分化而完全为海绵组织。然而,泽米科没有典型的海绵组织和传输组织分化。小刺双子铁、大头非洲铁、鳞叶木铁和摩尔大泽米的羽片具有粘液道而无工字厚壁组织,在小刺双子铁中粘液道与维管束对生,在另3种中则与维管束轮生;但粗壮角果铁、竹叶角果铁、佛州泽米、柔叶泽米、鳞秕泽米和短尖泽米的羽片则具有工字厚壁组织而没有粘液道,其中粗壮角果铁和竹叶角果铁的羽片工字厚壁组织仅与上表皮相连,而佛州泽米、柔叶泽米、鳞秕泽米和短尖泽米的羽片工字厚壁组织与上、下表皮都相连。羽片脉序和解剖学特征支持Stevenson将泽米铁科分为两亚科的观点。     

八种苏铁植物叶轴的比较解剖研究

对苏铁科和泽米铁科8种苏铁植物,即台湾苏铁(Cycas taiwaniana)、海南苏铁(C·hainanensis)、元江苏铁(C·parvulus)、单羽苏铁(C·simplicipinna)、滇南苏铁(C·diannanensis)、越南篦齿苏铁(C·elon-gata)、长刺大泽米铁(Macrozamia longispina)、双子铁(Dioon edule)的叶轴横切面结构进行了比较研究,以期为苏铁植物的系统演化和分类进一步提供解剖学依据,并探讨其解剖结构与生态的适应机制。结果表明,较原始的苏铁科和较进化的泽米铁科叶轴的横切面结构无论在表皮、机械组织、基本组织和维管组织,还是在后含物方面都存在着明显的不同;泽米铁科的大泽米铁属与双子铁属差异也较大;苏铁科科内的6个种则相似性稍大,表明它们是亲缘关系较密切的类群,但每个种都有各自的结构特点。越南篦齿苏铁的维管束排列方式和数目的增加方式与泽米铁科两个种的相似,因此推断它处于较进化的地位。研究还发现苏铁科种类的叶轴的近轴面均像叶片那样具有栅栏组织状同化组织存在。苏铁类植物叶轴具有旱生植物的解剖结构特征:角质层较厚、表皮细胞壁厚、机械组织发达、晶体较多、分泌道和维管束数目较多等结构特征。这些对研究苏铁纲各科及种类之间的进化与亲缘关系提供了佐证,同时揭示了苏铁纲这类古老的植物类群其多个属的种类能够经历如此漫长的地质年代而幸存下来,是由于其在长期演化过程中均形成了这些独特的结构特征,因而具备了相对应的生理功能,能够在恶劣的自然环境下,具备耐干旱、贫瘠、高温及耐盐碱等逆境的结果。     

托叶铁科(苏铁目)羽片脉序和羽片解剖学研究

详细研究了托叶铁科两属的2种代表植物Stangeria eriopus和Bowenia serrulata的羽片脉序和羽片解剖学,两个属在气孔器特征与不具副传输组织方面极为相似。而在气孔的分布,羽片脉序式样与叶缘形态,粘液道的有无,海绵组织与栅栏组织的分化。工字厚壁组织与表皮细胞垂周壁特征方面则有较大的差异。将这些特征与苏铁科和泽米铁科作了比较,并讨论了这些特征在系统学上的意义。研究结果支持Stevenson(1992)将该科分为两亚科以及托叶铁科是介入苏铁科与泽米铁科之间的观点。     

石竹属植物叶表皮特征及其系统学意义

用光学显微镜和扫描电镜,对石竹属12个种的植物叶表皮特征进行观察,统计并测量叶表皮气孔大小、气孔密度及气孔指数。结果表明,石竹属植物叶表皮细胞形态(表面观)为长方形和不规则多边形。乳突只存在于针叶石竹、高石竹和细茎石竹中。按气孔形状可将其分为了3个类型:椭圆形、卵圆形和长方形。研究结果对石竹属的系统分类和种间亲缘关系研究具有一定的参考价值。     

石蒜属植物叶微形态特征研究

借助显微和扫描电镜技术对石蒜属植物叶表皮微形态特征进行了研究。利用光学显微镜和扫描电子显微镜观察了石蒜属植物的叶表皮,统计并测量了气孔类型、气孔大小、气孔密度及气孔指数等,描述了气孔及气孔外拱盖的有关特征。结果表明：石蒜属植物叶表皮气孔器为无规则型,近轴面表皮细胞形状、气孔器类型、垂周壁式样、气孔大小及气孔外拱盖内缘种间无差异或极小,表明石蒜属植物为一自然分类群。而远轴面表皮细胞形状、气孔密度、气孔指数、气孔是否下陷、气孔外拱盖是否有蜡质纹饰等种间差异较大。根据远轴面叶表皮细胞形状及叶气孔特征,研究表明：换锦花、长筒石蒜和安徽石蒜,夏水仙、乳白石蒜与红蓝石蒜,石蒜与中国石蒜具有较近的亲缘关系。因此,叶微形态特征对探讨石蒜属植物种间亲缘关系具有一定的意义。     

27种木犀属植物叶表皮微形态特征的研究

利用光学显微镜和扫描电子显微镜观察了27种木犀属植物的叶表皮,测量并统计了气孔器类型、气孔大小、气孔密度、气孔指数及腺点密度等指标,以明确各种的叶表皮细胞形状及垂周壁式样、表皮角质膜、蜡质纹饰及气孔外拱盖的具体特征。结果显示:木犀属植物叶下表皮有气孔器,形状为圆形、椭圆形;气孔器类型多为不规则型,只有总状桂花和狭叶木犀为环列型;气孔器外围角质层有放射状、条状、环状、颗粒状等多种类型;叶表皮细胞形状有无规则形和多边形2种;下表皮腺点的数目远远大于上表皮。研究表明,木犀属植物气孔器和叶表皮细胞特征在种之间差异比较明显,可以作为种间鉴定的重要依据,具有重要的分类学意义。     

变豆菜属11种植物的叶表皮微形态特征研究

为探讨叶表皮微形态特征在变豆菜属植物中的系统及分类学意义,我们利用扫描电镜对变豆菜属11个种(13个居群)的叶表皮微形态特征进行了研究。结果表明,11种变豆菜属植物叶表皮微形态特征较稳定,上表皮细胞轮廓大多不清晰,初级蜡质纹饰均存在条状纹饰,表皮上均粘附着颗粒物;下表皮均存在气孔,气孔周围存在均匀分布的纹饰,气孔外拱盖表面大多有颗粒状纹饰,并且其二级纹饰类型、气孔周围纹饰、气孔外拱盖内缘纹饰等叶表皮微形态特征上存在一定差异。上述研究结果可为探讨变豆菜属类群界定及种间关系提供重要依据。     

中国北方鸢尾属植物叶片解剖结构特征及分类学价值研究

以中国北方生长的鸢尾属9种植物为研究对象,利用光学显微镜对叶表皮细胞形状及大小、气孔大小、气孔分布及气孔密度、气孔指数等叶表皮构造特征进行观察,并探讨了叶表皮特征在鸢尾属内各个亚属、亚组间的分类学价值,结果表明：表皮细胞的形状和大小显示了同亚属或同亚组植物之间较为明显的亲缘关系,在区分鸢尾属下不同亚属或亚组植物上也有一定的分类学价值。气孔密度和气孔指数在鸢尾属内分类学价值不大,但却能很好地反映不同鸢尾属植物与生境之间的密切关系。并从表皮构造特征上证实了野鸢尾与射干有很强的亲缘关系,且近于鸢尾属内的其他植物的结论;此外,通过对鸢尾属植物叶横切解剖结构的观察：从维管束、横切面形状、表皮细胞与角质层、乳突、气孔、气室大小、叶肉细胞的分化这7个较为明显的特征上的相关性和差异性,探讨了由于生境的不同而产生的植物形态结构的差异。     

中国北方鸢尾属植物叶片解剖结构特征及分类学价值研究

以中国北方生长的鸢尾属9种植物为研究对象,利用光学显微镜对叶表皮细胞形状及大小、气孔大小、气孔分布及气孔密度、气孔指数等叶表皮构造特征进行观察,并探讨了叶表皮特征在鸢尾属内各个亚属、亚组间的分类学价值,结果表明：表皮细胞的形状和大小显示了同亚属或同亚组植物之间较为明显的亲缘关系,在区分鸢尾属下不同亚属或亚组植物上也有一定的分类学价值。气孔密度和气孔指数在鸢尾属内分类学价值不大,但却能很好地反映不同鸢尾属植物与生境之间的密切关系。并从表皮构造特征上证实了野鸢尾与射干有很强的亲缘关系,且近于鸢尾属内的其他植物的结论;此外,通过对鸢尾属植物叶横切解剖结构的观察：从维管束、横切面形状、表皮细胞与角质层、乳突、气孔、气室大小、叶肉细胞的分化这7个较为明显的特征上的相关性和差异性,探讨了由于生境的不同而产生的植物形态结构的差异。     

A phylogeny of cycads (Cycadales) inferred from chloroplast matK gene, trnK intron, and nuclear rDNA ITS region

Phylogenetic relationships among the three families and 12 living genera of cycads were reconstructed by distance and parsimony criteria using three markers: the chloroplast matK gene, the chloroplast trnK intron and the nuclear ITS/5.8S rDNA sequence. All datasets indicate that Cycadaceae (including only the genus Cycas) is remotely related to other cycads, in which Dioon was resolved as the basal-most clade, followed by Bowenia and a clade containing the remaining nine genera. Encephalartos and Lepidozamia are closer to each other than to Macrozamia. The African genus Stangeria is embedded within the New World subfamily Zamiodeae. Therefore, Bowenia is an unlikely sister to Stangeria, contrary to the view that they form the Stangeriaceae. The generic status of Dyerocycas and Chigua is unsupportable as they are paraphyletic with Cycas and the Zamia, respectively. Nonsense mutations in the matK gene and indels in the other two datasets lend evidence to reinforce the above conclusions. According to the phylogenies, the past geography of the genera of cycads and the evolution of character states are hypothesized and discussed. Within the suborder Zamiieae, Stangeria, and the tribe Zamieae evolved significantly faster than other genera. The matK gene and ITS/5.8S region contain more useful information than the trnK intron in addressing phylogeny. Redelimitations of Zamiaceae, Stangeriaceae, subfamily Encephalartoideae and subtribe Macrozamiineae are necessary.     

Ten microsatellite loci from Zamia integrifolia (Zamiaceae)

Ten microsatellite loci isolated from Zamia integrifolia are described. All 10 are polymorphic, with three to 10 alleles across 36 members of a single population from South Florida. Heterozygosities ranged from 0.139 to 0.889. Two loci depart significantly from Hardy–Weinberg equilibrium, and exhibit heterozygote deficiency. One locus pair exhibits significant linkage disequilibrium. The primers have also successfully amplified loci from Zamia portoricensis and Zamia ambliphyllidia. These loci will be utilized for population studies in the Caribbean Zamia pumila complex.     

Modulatory effects of Duguetia furfuracea (A. St. Hil) Benth. and Hook. f. in Drosophila melanogaster somatic and germinative cells

Mutagenic and antimutagenic activities of the medicinal plant Duguetia furfuracea were assessed using SMART/wing and ring-X-loss tests. For the ring-X-loss test, 2- to 3-day-old Drosophila melanogaster ring-X-lineage males and virgin ywsn3 females received D. furfuracea infusion at doses of 0.085, 0.042, or 0.014 g/mL for 24 h. We found that D. furfuracea did not produce any mutagenic effects in D. melanogaster germinative cells. The somatic cells of D. melanogaster were analyzed using the SMART/wing test involving three lineages - mwh, flr3, and ORR - and the same doses of D. furfuracea infusion employed in the ring-X-loss test, as well as 20 mM urethane. The results of both standard (ST) and high bioactivation (HB) crosses showed absence of mutagenic activity of D. furfuracea. In contrast, in both ST and HB crosses, we observed a modulatory effect of D. furfuracea against the genotoxic activity of urethane.     

A phylogenetic analysis of American Zamiaceae (Cycadales) using chloroplast DNA restriction fragment length polymorphisms

A phylogenetic analysis of American cycad genera, all belonging to the family Zamiaceae, was attempted using chloroplast DNA restriction fragment polymorphisms.Ceratozamia mexicana Brongn.,Chigua restrepoi D. Stevenson,Dioon edule Lindley,Microcycas calocoma (Miq.) A. DC.,Zamia fischeri Miq., andZamia skinneri Warsz. ex A. Dietrich were used as representatives of the genera.Cycas revoluta Thunb., belonging to the family Cycadaceae, was used as an outgroup, following previous morphological works. One hundred and forty-one shared restriction fragments were scored for presence/absence and both Wagner and Dollo parsimony analyses were performed. The single, fully resolved, most parsimonious trees obtained from the analyses were topologically identical and perfectly matched previous morphology-based phylogenetic hypotheses. Statistical evaluation of the data showed a good reliability for the obtained phylogeny.Dioon edule, belonging to a different subfamily and more primitive on morphological grounds, proved to be the most primitive among American cycads as inferred from the molecular data;Chigua restrepoi, never analyzed before on cladistic grounds, was found to be the sister group of the genusZamia.     

Azoxyglycoside content and beta-glycosidase activities in leaves of various cycads

Azoxyglycoside contents in leaves of 32 cycad species belonging to 10 cycad genera and the seeds of 4 Encephalartos species were analyzed by HPLC with a YMC-PA03 amide column. Azoxyglycosides were detected in mature leaves of 14 cycad species including 2 Bowenia, 2 Lepidozamia, 1 Microcycas, and 1 Stangeria species, but not in mature leaves of 18 other cycad species; 2 of 3 Ceratozamia, 1 of 3 Cycas, 3 of 3 Dioon, 10 of 11 Encephalartos, 1 of 3 Macrozamia and 1 of 3 Zamia species analyzed. The ratios of beta-glycosidase activity toward cycasin and macrozamin in extracts from the leaves of 9 species belonging to 9 genera were measured. The hydrolysis of cycasin was higher in the leaf extracts of Cycas revoluta, Bowenia spectabilis, Stangeria eriopus and Ceratozamia mexicana, whereas in Lepidozamia hopei, the hydrolysis levels of cycasin and macrozamin were similar. On the other hand, activity toward macrozamin was higher in Dioon edule, Encephalartos villosus, Macrozamia miquelii and Zamia fischeri. The hydrolytic activities in most species were estimated to be sufficient for the release of methylazoxymethanol in leaves analogous to the cyanogenesis of cyanogenic plants. Therefore, hydrolysis of azoxyglycosides by endogenous glycosidase in leaves seems to occur by accidental injury of leaves. However, in M. miquelii leaf extract, hydrolytic activity toward macrozamin was high and the activity toward cycasin was very low, though only cycasin was found in the leaves of this species.     

Caterpillars of Eumaeus childrenae (Lepidoptera: Lycaenidae) feeding on two species of cycads (Zamiaceae) in the Huasteca region, Mexico

There are few genera of butterflies that feed on cycads. Among them the genus Eumaeus (Lycaenidae) presents aposematic coloration in all its life stages. In this work we report for the first time the herbivory of young leaflets of Ceratozamia mexicana and Zamia fischeri (Zamiaceae) by caterpillars of E. childrenae in their natural habitat in the Huasteca region, Mexico.     

Histological changes during maturation in male and female cones of the cycad Zamia furfuracea and their significance in relation to pollination biology

The cycad Zamia furfuracea L.Fil. Is pollinated by a curculionid beetle, Rhopalotria mollis Sharp which completes its life cycle in male cones of the cycad, and effectively pollinates female coneS. Idioblasts within parenchyma in both male and female cones appear to contain toxic compounds, including at least one neurotoxin, 2-amino-3-(methylamino) propanoic acid (BMAA), and a toxic glycoside, methylazoxymethanol-/!-primeveroside (macrozamin). Idioblasts appear structurally unmodified in male cones throughout the period of pollen maturation, and feeding weevils consume much of the starch-rich microsporophyll parenchyma tissue, including idioblastS. During this activity no appreciable change in morphology or staining reactions of male-cone idioblasts is detectable. Prior to pollen receptivity, female-cone idioblasts resemble those of male cones. Thereafter, many female-cone idioblasts show marked changes in morphology and content not caused by the weevils themselveS. Idioblast changes in female cones are probably associated with the defence of female-cone resources against predation by animals, including pollinating weevils, and may relate to mobilization of toxinS. Absence of similar morphological changes in male-cone idioblasts is correlated with toxin sequestration, enabling the pollinator to breed and feed without intoxication.     

KARYOTYPIC DATA ON NORTH AND CENTRAL AMERICAN ZAMIACEAE (CYCADALES) AND THEIR PHYLOGENETIC IMPLICATIONS

Chromosome numbers and karyotypes of species from four American Zamiaceae (Cycadales) are reported. Zamia shows interspecific and intraspecific chromosome variation, whereas Microcycas, Ceratozamia, and Dioon have constant karyotypes within each genus. In Zamia, all karyotypes have the same number of submetacentric and acrocentric chromosomes, but they differ in the number of metacentric and telocentric chromosomes. Centric fission of metacentric chromosomes is proposed to explain the karyotypic variation in this genus. Zamia shows karyological relationships with Microcycas and Ceratozamia, whereas Dioon appears very distinct from the other American cycad genera. Affinity among Zamia, Ceratozamia, and Microcycas karyotypes and distinctiveness of Dioon karyotypes are supported by comparative analysis of phenotypic characters in the four genera.     

Monitoring endemic plant extinction in Veracruz, Mexico

We present species extinction information based directly on field work on six endemic vascular plants of Veracruz. Amongst 22 species that have been reported to consist of very few individuals for the State, seven of them are endemic to Veracruz. We looked for six of these species in previously recorded sites to determine if they are totally extinct. We determined the status of the extant species and their actual habitat and populations. The species studied included: Antirhea aromatica, Diospyros riojae, Eugenia mozomboensis, Impatiens mexicana, Hyperbaena jalcomulcensis and Zamia inermis. We located these in fragments of tropical and dry forests. Juvenile plants of the Zamia and Eugenia were not seen in the field.