Wide-band tracheids in leaves of genera in Aizoaceae: the systematic occurrence of a novel cell type and its implications for the monophyly of the subfamily Ruschioideae

 Stem and leaf anatomical characters of succulent plants in families of the order Caryophyllales were examined to determine phylogenetic and evolutionary trends within these families. Wide-band tracheids, novel tracheids having wide secondary walls hypothesized to prevent cell collapse under water stress, were found in three families–Aizoaceae, Cactaceae, and Portulacaceae. Wide-band tracheids are hypothesized to be a unique adaptation to severe drought conditions prevalent in the areas of origin for these families. Species of 89 genera of Aizoaceae were examined for the occurrence of these tracheids. If present, wide-band tracheids occurred only in leaves. Of the five subfamilies examined, these tracheids were found only in the subfamily Ruschioideae, but not in the putative basal genera of the ruschioids. The presence of wide-band tracheids is an apomorphic character for genera of Ruschioideae with the exception of the basal genera, and also suggests that further characters are needed to understand the alliance of the Apatesia and Cleretum groups with other ruschioid groups. Received April 19, 2000 Accepted December 26, 2000     

湖北省楠属植物叶表皮微形态特征及其分类学意义

【目的】楠属（Phoebe）各物种在形态学方面差异甚微,种间界限模糊,物种的识别鉴定较为困难,尤其在缺少花、果的时期。叶微形态特征对植物种间界定具有重要价值,但目前楠属植物叶显微特征的研究仍然较少。【方法】利用体视显微镜、光学显微镜对湖北省楠属8种及1变种的叶形态和微形态进行观察,并测定分析各物种气孔、表皮毛的质量和数量性状,以期为楠属植物的识别和鉴定提供必要依据。【结果】结果表明,叶形态有大型叶、中型叶、小型叶和不规则叶4种类型;毛被类型有粗短柔毛、细短柔毛、长柔毛、混生短柔毛和长柔毛（脉上被长柔毛）4种。毛密度在湘楠（200根/mm2）与闽楠、浙江楠、紫楠（低于100根/mm2）之间差异显著。表皮细胞类型为多边形或不规则形,垂周壁为平直-弓形、浅波或波状。气孔除披针叶楠、闽楠、裂叶白楠为近圆形外,其余物种均为宽椭圆形。气孔密度以紫楠最高,山楠和湘楠最低。此外,气孔大小与气孔密度之间,毛长度与毛密度之间存在负相关关系。【结论】研究表明,叶形态和微形态的特征组合可作为9种楠属植物鉴定和区分的必要依据,可为楠属植物识别和种间界定提供参考。     

Medullary structure differences in Gelidium and Pterocladia (Gelidiales, Rhodophyceae): Taxonomic meaning

Study of the apical portions of vegetative thalli of 21 species of the genera Gelidium and Pterocladia (Gelidiales-Rhodophyta) revealed the existence of six patterns of medullary structure. Each pattern is characterized by the organization of the medullary tissue and the changes in cellular dimensions from apex to subapex. These characters can be used to separate groups of species within each genus.     

Taxonomic significance of leaf anatomy of Aniselytron (Poaceae) as an evidence to support its generic validity against Calamagrostis s. l.

A comparative study of leaf anatomy on Aniselytron Merr. and Calamagrostis Adans. s. l. was conducted to review the systematic status of Aniselytron Merr. Calamagrostis s. l. exhibits wide variation in many features, but basic leaf structures of the genus remain constant: absence of a midrib-keel; median and large vascular bundles are central, with double sheaths, accompanied by girders both adaxially and abaxially; prickles have a bulbous base and are not sunken; the abaxial epidermal cells are short and wide and relatively thick-walled. Aniselytron differs from Calamagrostis s. l. in: midrib-keel is present, consisting of a large central bundle with small ones on either side; all vascular bundles are abaxially situated, with abaxial girders only, parenchyma takes the place of the adaxial sclerenchyma; the bases of the prickles are sunken and are not bulbous; the abaxial epidermal cells are tall and thin-walled. These distinct anatomical features, in combination with the differences in spikelet structure and habitat, suggest that Aniselytron should be generically separated from and not merged with Calamagrostis s. l. Due to the adaxial parenchyma in the midrib which has never been found in Pooideae, Aniselytron might have a relationship with some other subfamily.     

The systematic significance of the endothecium in Begoniaceae

The endothecial thickening patterns in 173 species, representing the three genera of Begoniaceae, were investigated using cleared macerated anthers. Begoniaceae contain taxa with U-shaped thickenings, perforate base plates, entire base plates, tympanate base plates, anticlinal bars, and taxa that lack endothecial thickenings. The degree of correlation between these endothecial classes and accepted taxonomic boundaries varies: some classes are confined to a single taxonomic unit (e.g. absence of thickenings, non-perforate tympanate base plates) while others are present in several taxonomic units (e.g. U-shapes, perforate base plates). This study provides an improved understanding of the diversity of endothecial patterns in a large genus and indicates that in the Begoniaceae the endothecium is of moderate systematic value within and between closely related sections in Begonia and in Symbegonia . We conclude that the endothecium exhibits high levels of homoplasy between distantly related sections of Begonia . In addition, we show that in contrast to past observations of the endothecium in dicotyledons, apical anther dehiscence in the Begoniaceae is not correlated with a loss of endothecial thickening.     

山茶属的叶表皮形态及其分类学意义

在光学显微镜下观察了山茶属（Camellia)19个组36个代表种的叶表皮形态,发现上述植物的叶上下表皮细胞表面观形状均为不规则形,气孔器仅在下表皮存在,且一致为环列型;对上述植物中18个组30个种的叶下表皮进行扫描电镜观察,其特片为：气孔形状为梭形或长卵形,气孔外拱盖内缘光滑或呈浅波状,波状,气孔器附近的角质膜平坦或皱褶,表面光滑或有多种纹饰,这些特征可作为区分种或变种的依据,但与植物的外部形态等特征没有相关性。     

8种蒲公英属植物叶柄解剖学特征与分类学意义

采用石蜡切片法在光学显微镜下观察8种蒲公英属(Taraxacum)植物叶柄中部横切面的解剖特征.结果表明:8种蒲公英属植物不同种叶柄中部横切面形状不同,可分为椭圆形、长椭圆形和扁椭圆形.维管束类型可分为两大类,周韧和近周韧,且每种蒲公英的维管束数目和大小都不尽相同.这些特征在种之间差异比较明显,可作为种间分类鉴定的重要依据,并为蒲公英属植物亲缘关系鉴定提供了解剖学证据.     

Numerical Taxonomic Studies of Hemerocallis (Liliaceae) from China

Taxonomic studies of 11 taxa in Hemerocallis from China were conducted using cluster analysis and principal components analysis. The taxa were grouped into four clusters. The Cluster one includs H. citrina, H. lilioasphodelus, H. minor and H. multiflora ; the second cluster H. dumortieri and H. middendorfii ; the third cluster H. plicata, H. forresti and H. nana; and the fourth cluster di-and triploid of H. fulva. Relationships between the taxa within clusters as well as the subdivision of the genus are discussed.     

Taxonomic Identity in Microbial Eukaryotes: A Practical Approach Using the Testate Amoeba Centropyxis to Resolve Conflicts Between Old and New Taxonomic Descriptions

ABSTRACT. The present work focuses on 12 taxa of the genus Centropyxis Stein, 1857 to explore the conflict between traditional and contemporary taxonomic practices. We examined the morphology, biometry, and ecology of 2,120 Centropyxis individuals collected from Tiete River, Sao Paulo, Brazil; with these new data we studied the consistency of previously described species, varieties, and forms. We encountered transitional forms of test morphology that undermine specific and varietal distinctions for three species and nine varieties. Biometrical analyses made comparing the organisms at the species level suggest a lack of separation between Centropyxis aculeata and Centropyxis discoides, and a possible distinction for Centropyxis ecornis based on spine characteristics. However, incongruence between recent and previous surveys makes taking any taxonomic–nomenclatural actions inadvisable, as they would only add to the confusion. We suggest an explicit and objective taxonomic practice in order to enhance our taxonomic and species concepts for microbial eukaryotes. This will allow more precise inferences of taxon identity for studies in other areas.     

Taxonomic notes on the genus Crataegus (Rosaceae) in Turkey

The Turkish Crataegus taxa were investigated using morphological, palynological, and anatomical characters. A new series ( Crataegus Section Crataegus Series Peshmenia ), two new species ( Crataegus peshmenii and Crataegus christensenii ), and one variety ( Crataegus rhipidophylla var. kutahyaensis ) are described. Furthermore, Crataegus  ×  browicziana has been assigned to Crataegus rhipidophylla with a new status. Illustrations of the described taxa and their distribution map are also given. The lectotype for Crataegus yaltirikii is designated here.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 231–240.     

Photosynthetic and structural acclimation to light direction in vertical leaves of Silphium terebinthinaceum

The azimuth of vertical leaves of Silphium terebinthinaceum profoundly influenced total daily irradiance as well as the proportion of direct versus diffuse light incident on the adaxial and abaxial leaf surface. These differences caused structural and physiological adjustments in leaves that affected photosynthetic performance. Leaves with the adaxial surface facing East received equal daily integrated irradiance on each surface, and these leaves had similar photosynthetic rates when irradiated on either the adaxial or abaxial surface. The adaxial surface of East-facing leaves was also the only surface to receive more direct than diffuse irradiance and this was the only leaf side which had a clearly defined columnar palisade layer. A potential cost of constructing East-facing leaves with symmetrical photosynthetic capcity was a 25% higher specific leaf mass and increased leaf thickness in comparison to asymmetrical South-facing leaves. The adaxial surface of South-facing leaves received approximately three times more daily integrated irradiance than the abaxial surface. When measured at saturating CO₂ and irradiance, these leaves had 42% higher photosynthetic rates when irradiated on the adaxial surface than when irradiated on the abaxial surface. However, there was no difference in photosynthesis for these leaves when irradiated on either surface when measurements were made at ambient CO₂. Stomatal distribution (mean adaxial/abaxial stomatal density = 0.61) was unaffected by leaf orientation. Thus, the potential for high photosynthetic rates of adaxial palisade cells in South-facing leaves at ambient CO₂ concentrations may have been constrained by stomatal limitations to gas exchange. The distribution of soluble protein and chlorophyll within leaves suggests that palisade and spongy mesophyll cells acclimated to their local light environment. The protein/chlorophyll ratio was high in the palisade layers and decreased in the spongy mesophyll cells, presumably corresponding to the attentuation of light as it penetrates leaves. Unlike some species, the chlorophyll a/b ratio and the degree of thylakoid stacking was uniform throughout the thickness of the leaf. It appears that sun-shade acclimation among cell layers of Silphium terebinthinaceum leaves is accomplished without adjustment to the chlorophyll a/b ratio or to thylakoid membrane structure.     

A Numerical Taxonomic Study of Citrus and Its Close Relatives

Fifty nine taxa of Citrus, Fortunella and Poncirus were studied by hierarchical agglomerative clustering analysis and quantas type 3 analysis using 86 morphological characters. Five affinity groups were obtained in Citrus. The first group includes C. medica, C. limon, C. limonia, C. aurantifolia and C. iambhiri; the second includes C. grandis, C. aurantium, C. sinensis and C. paradisi; the third is mandarin (C. reticulata); the forth is C. ichangensis; The last is C. hongheensis. Mandarin oranges show two subgroups: one comprise satsuma, King, Shagan, Tankan and Bendiguangju, and the other consists of the remaining typical mandrins. The two papeda oranges, honghe papeda and ichang papeda, could not be clustered into the same group, indicating that they might have evolved from two compeletly different ancestors. Pumelos(C. grandis) show some relationships to honghe papeda orange. C. limonia is assumed to be a hybrid between rough lemon and mandarin. The sweet orange(C. sinensis) is considered to be the offspring of pomelo and mandarin. Zhekiang jinju a small mandarin generally considered similar to calamondin in China, should be a true mandarin orange based on our results. Poncirus was well distinguished from the other two genera, Citrus and Fortunella, by the numerical methods used in this study. Our results show that citron (C. medica), mandarin (C. reticulata) and pumelo (C. grandis) are the original species of the subgenus Citrus, which was congruent with the re-sults obtained by Barrett and Soost (1976), Potvin (1983) and Handa (1985).     

伞形科藁本属20种植物的果实特征及其分类学意义

采用扫描电镜方法对中国藁本属20种及山芎属1种植物的果实表面微形态进行首次研究,并对其中15种进行果实解剖特征观察。结果表明:藁本属植物果实微形态在外果皮表面突起度、细胞轮廓、表面纹饰和表皮分泌物上表现出丰富的多样性;在果实解剖特征上,果棱形状、油管数目、胚乳形状等种间差异明显且稳定,而种内居群间无变异,可作为藁本属种间鉴定及种间关系探讨的重要参考性状。结合前人对伞形科其他类群果实微形态与解剖结构特征的研究及近年来分子系统学的证据,得出如下结论:(1)藁本属不是一个自然类群;(2)支持拟藁本属归入藁本属;(3)对藁本属部分种的系统位置和种间亲缘关系进行了讨论。     

青藓科（Brachytheciaceae）植物假鳞毛形态及其分类学意义

青藓科是侧蒴藓类植物中种类最为丰富、分类学问题较多的类群之一。以青藓科19属、44种,594份标本为研究对象,对其假鳞毛特征进行了系统研究。结果表明：①青藓科假鳞毛均为三角形至半圆形的叶状假鳞毛;根据其顶端特征又可划分为两种类型：顶端平截或钝,顶端具毛尖;②除青藓属（Brachythecium）外,其余18属内不同种间的假鳞毛形态基本一致;③假鳞毛形态特征在青藓科植物属级水平分类上具有一定的分类学价值。     

Photosynthetic symmetry of sun and shade leaves of different orientations

Summary The photosynthetic responses to light of leaves irradiated on the adaxial or abaxial surfaces, were measured for plants with contrasting leaf orientations. For vertical-leaf species of open habitats (Eryngium yuccifolium and Silphium terebinthinaceum), photosynthetic rates were identical when irradiated on either surface. However, for horizontal-leaf species of open habitats (Ambrosia trifida and Solidago canadensis), light-saturated rates of photosynthesis for adaxial irradiation were 19 to 37% higher than rates for abaxial irradiation. Leaves of understory plants (Asarum canadense and Hydrophyllum canadense) were functionally symmetrical although they had horizontal orientation. Photosynthetic rates were measured at saturating CO₂, thus differences in the response to incident irradiance presumably resulted from complex interactions of light and leaf optical properties rather than from stomatal effects. Differences in absorptance (400–700 nm) among leaf surfaces were evident for horizontal-leaf species but the primary determinant of functional symmetry was leaf anatomy. Functionally symmetrical leaves had upper and lower palisade layers of equal thickness (vertical leaves of open habitats) or were composed primarily of a single layer of photosynthetic cells (horizontal leaves of understory habitats). Photosynthetic symmetry of vertical-leaf species may be an adaptation to maximize daily integrated carbon gain and water-use efficiency, whereas asymmetry of horizontal-leaf species may be an adaptation to maximize daily integrated carbon gain and photosynthetic nutrient-use efficiency.