Artichoke Leaf Morphology and Surface Features in Different Micropropagation Stages

Artichoke (Cynara scolymus L.) leaf size and shape, glandular and covering trichomes, stomatal density, stomata shape, pore area and epicuticular waxes during micropropagation stages were studied by scanning electron microscopy (SEM) and morphometric analysis with the aim to improve the survival rate after transfer to greenhouse conditions. Leaves from in vitro shoots at the proliferation stage showed a spatular shape, ring-shaped stomata, a large number of glandular trichomes and juvenile covering hairs, but failed to show any epicuticular waxes. Leaves from in vitro plants at the root elongation stage showed a lanceolated elliptic shape with a serrated border, elliptical stomata, decreased pore area percentage, stomatal density, and mature covering trichomes. One week after transfer to ex vitro conditions, epicuticular waxes appeared on the leaf surface and stomata and pore area were smaller as compared to in vitro plants. Artichoke acclimatization may be improved by hormonal stimulation of root development, since useful morphological changes on leaves occurred during root elongation.     

Infraspecific variation of leaf anatomy in Origanum vulgare grown wild in Greece

The histological components of the leaf were studied in dried herbarium material of the three Origanum vulgare subspecies (subsp. hirtum , subsp. viridulum and subsp. vulgare ) grown wild in Greece. These three, geographically distinct, taxa showed remarkable differences in their leaves. The leaves of subsp. hirtum grown in the Mediterranean climatic zone of Greece are characterized by thick cutinized outer walls of the epidermal cells and a thick mesophyll with highly developed chlorophyllous tissues. Peltate glandular trichomes and stomata are numerous on bom leaf surfaces. The thickness of the mesophyll decreases in the other two subspecies grown in the northern part of the country, where a Continental type of climate occurs. The number of glandular trichomes and stomata also decreases. Besides these differences, a noticeable reduction in the size of the essential oil-accumulating subcuticular chamber of the glandular trichomes and in the number of the peribasal cells, has also been recorded in die plants of subsp. vulgare and viridulum.     

线纹香茶菜叶上腺毛发育的细胞学研究

为进行中药溪黄草基原植物的品种鉴定,采用光镜和电镜对线纹香茶菜(原变种)[Isodon lophanthoides var.lophanthoides]叶上腺毛的发育进行细胞学研究。结果表明,线纹香茶菜具有头状腺毛和盾状腺毛2种类型。头状腺毛无色透明,由1个基细胞、1个柄细胞和1或2个头部分泌细胞构成;盾状腺毛为红色,由1或2个基细胞、1个柄细胞和4~8个分泌细胞构成头部。2种腺毛均由原表皮细胞经两次平周分裂形成,后因柄细胞和头部细胞所处的分化状态不同而形成两类腺毛。2种腺毛超微结构表明,质体、高尔基体和粗面内质网为主要分泌物产生和运输的细胞器。当盾状腺毛成熟时,角质层下间隙充满了分泌物,其分泌物的性质很可能决定了线纹香茶菜腺毛的颜色。     

Comparative anatomy of leaves and stems in some species of the South American genus Chrysolaena (Vernonieae,Asteraceae) and taxonomic implications

Vegetative anatomical features are poorly known in the South American genus Chrysolaena. In this study, leaves and stems of six Chrysolaena species were described and compared morphologically and anatomically using diaphanization, microtome serial sectioning and scanning electron microscopy. The species differed in leaf epidermis, type of stomata, shape of anticlinal walls of epidermal cells, trichome density, and presence or absence in stems of small air spaces in the cortical parenchyma and of druse‐shaped oxalate crystals. Furthermore, glandular trichomes and three types of non‐glandular trichomes with different number of basal cells were identified on leaves and stems. Collectively, these features proved instrumental to discriminate among the six studied species, suggesting that leaves and stems of Chrysolaena can represent a source for taxonomically useful characters. We also discuss anatomical features in relation to the environmental conditions in the species’ habitats.     

Trichome morphology provides phylogenetically informative characters for Tremandra, Platytheca and Tetratheca (former Tremandraceae)

Summary Trichomes of Tremandra R.Br. ex DC., Platytheca Steetz and Tetratheca Sm. (Elaeocarpaceae, former Tremandraceae), together with two outgroup species of Elaeocarpus L., are illustrated using scanning electron microscopy, and their distribution on various plant organs is documented. Various trichomes types were identified that relate taxa: simple hairs, stellate hairs, short glandular trichomes, long glandular trichomes, and three forms of tubercules. Both outgroup and ingroup taxa have simple hairs. Stellate hairs are confirmed as unique to Tremandra. Prominent and sculptured multicelled tubercules, some bearing a stout hair, are characteristic of Platytheca. Smaller multicelled tubercules occur in both Platytheca and Tetratheca, except for the Western Australian taxon Te. filiformis Benth. (possibly plesiomorphic). Unicellular tubercules (papilla) characterise two species of Tetratheca. Short glandular trichomes, usually found on the ovary, also occur in both of these genera but not in all species (possibly secondary losses), while long glandular trichomes, usually on stems and leaves, occur only in some groups of Tetratheca. Within Tetratheca, Western Australian taxa that have five-merous flowers fall into three ‘groups’: seven species (together with one from South Australia) that have short glandular trichomes but no long glandular trichomes; six species that have long glandular trichomes but no short glandular trichomes; and four species that have both trichome types. All other species of Tetratheca have four-merous flowers and form two ‘groups’: 12 eastern species (including one from South Australia) that have both short glandular trichomes and long glandular trichomes; 4 western species and six eastern species that lack short glandular trichomes. On the basis of these characters, a phylogenetic hypothesis for the three genera is presented.     

地黄叶和茎的解剖学及组织化学研究

采用解剖学和组织化学方法对地黄叶和茎的显微结构以及梓醇、多糖的分布进行观察研究,以明确梓醇和多糖在地黄叶和茎中的分布特征。结果显示:(1)地黄叶的上、下表皮均分布有腺毛和非腺毛,腺毛都属于头状腺毛,包括长柄和短柄的头状腺毛,两类腺毛的分泌物化学成分主要是黄酮和多糖;叶的上、下表皮上都分布有无规则型气孔,下表皮的气孔密度比上表皮的大,但气孔指数相差不大;栅栏组织由2～3层薄壁细胞构成,排列紧密,海绵组织薄壁细胞形状无规则,细胞间隙大。(2)组织化学研究表明,海绵组织中黄斑样的薄壁细胞是梓醇和多糖的贮存场所,这类薄壁细胞在叶片边缘的齿末端处最为集中,茎的皮层、韧皮部和木质部的薄壁细胞也都是梓醇和多糖的贮存场所。     

Comparative morphology of the leaf epidermis in the genera Codonanthe (Martius) Hanstein and Nematanthus Schrader (Gesneriaceae)*

The leaf epidermis of 14 species ofCodonanthe and 10 species of Nematanthus has been examined. Species of Codonanthe section Codonanthe are geographically restricted to south-eastern Brazil, and are diploid. They possess multicellular-uniseriate nonglandular trichomes, glandular trichomes with a four-celled head and a short body, anisocytic stomata and lack extrafloral nectaries. Species of Codonanthe section Spathuliformae and Codonanthe subgenus Codonanthella are distributed from southern Mexico through Central America to north-western South America and are tetraploid. They possess unicellular non-glandular trichomes (except C. caribaea), glandular trichomes with a two-celled head (except C. caribaea) and a short body, anisocytic stomata and extrafloral nectaries (except C. caribaea). All Nematanthus species are distributed in south-eastern Brazil and are diploid (N=8). Six species of Nematanthus consistently have multicellular-uniseriate nonglandular trichomes, glandular trichomes with a four-celled head and a short (unicellular) or long (multicellular) body, anisocytic stomata and lack extrafloral nectaries. Four species of Nematanthus have multicellular-uniseriate non-glandular trichomes, glandular trichomes with a head of more than four cells and a short body, anisocytic and helicocytic stomata and lack extrafloral nectaries.     

A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.     

An investigation of the foliar trichomes of Tetradenia riparia (Hochst.) Codd [Lamiaceae]: An important medicinal plant of Southern Africa

The morphology and distribution of leaf trichomes of Tetradenia riparia were studied using light and scanning microscopy. Three morphologically distinct types of trichomes were observed on T. riparia leaf surfaces: glandular capitate (short and long stalked), peltate and non-glandular. The glandular and non-glandular trichomes were present in abundance on both the adaxial and abaxial surfaces. Young leaves were densely covered with trichomes; however, the density of trichomes decreases progressively with leaf maturity. This suggests that the trichomes are established early in leaf differentiation and their density decreases with leaf development and age.     

29种中国野豌豆属植物叶表皮微形态特征及其系统学意义

应用光学显微镜和扫描电子显微镜对29种野豌豆属植物叶表皮微形态特征进行了观察。结果显示:叶表皮细胞形状有无规则形和多边形2种,垂周壁式样有深波状、浅波状和平直-弓形;表皮角质层纹饰微形态多样,大多数植物叶片表面不具有腺毛或仅中脉有,少数植物叶片表面具腺毛;部分叶表皮上有柔毛,少数植物无毛。气孔器存在于上表皮、下表皮、或上下表皮均有,形状为椭圆形、卵圆形,均为无规则型。野豌豆属植物叶表皮的这些微形态特征,在属内组间没有明确的规律性,但可为探讨该属种间的分类学及亲缘关系提供依据。     

Trichoderma species form endophytic associations within Theobroma cacao trichomes

Trichoderma species are usually considered soil organisms that colonize plant roots, sometimes forming a symbiotic relationship. Recent studies demonstrate that Trichoderma species are also capable of colonizing the above ground tissues of Theobroma cacao (cacao) in what has been characterized as an endophytic relationship. Trichoderma species can be re-isolated from surface sterilized cacao stem tissue, including the bark and xylem, the apical meristem, and to a lesser degree from leaves. SEM analysis of cacao stems colonized by strains of four Trichoderma species (Trichoderma ovalisporum-DIS 70a, Trichoderma hamatum-DIS 219b, Trichoderma koningiopsis-DIS 172ai, or Trichoderma harzianum-DIS 219f) showed a preference for surface colonization of glandular trichomes versus non-glandular trichomes. The Trichoderma strains colonized the glandular trichome tips and formed swellings resembling appresoria. Hyphae were observed emerging from the glandular trichomes on surface sterilized stems from cacao seedlings that had been inoculated with each of the four Trichoderma strains. Fungal hyphae were observed under the microscope emerging from the trichomes as soon as 6 h after their isolation from surface sterilized cacao seedling stems. Hyphae were also observed, in some cases, emerging from stalk cells opposite the trichome head. Repeated single trichome/hyphae isolations verified that the emerging hyphae were the Trichoderma strains with which the cacao seedlings had been inoculated. Strains of four Trichoderma species were able to enter glandular trichomes during the colonization of cacao stems where they survived surface sterilization and could be re-isolated. The penetration of cacao trichomes may provide the entry point for Trichoderma species into the cacao stem allowing systemic colonization of this tissue.     

Developmental plasticity in birch leaves: defoliation causes a shift from glandular to nonglandular trichomes

The structures on leaf surfaces, e.g. trichomes, can act as effective antiherbivory mechanisms as chemical repellents. Structural defences usually represent constitutive resistance, but there are also a few cases of inducible morphological defences. We tested whether defoliation may induce changes in trichome production in white birch (Betula pubescens). The studied birches were either 0, 50 or 100% defoliated during the previous or current summer, and we measured the alterations in the production of glandular vs. nonglandular leaf trichomes, developmental instability (fluctuating asymmetry, FA) and leaf and shoot growth. We detected a clear shift from glandular to nonglandular leaf trichomes following previous‐year defoliation but not after current‐year defoliation. Furthermore, the density of nonglandular trichomes around the mid‐vein of leaves increased following previous‐year defoliation but decreased after current‐year defoliation. While leaf and shoot growth showed a distinct decrease in response to defoliation, FA turned out to be less sensitive. Consequently, previous‐year defoliation can induce the production of nonglandular trichomes in birch leaves. Because this response was accompanied by a reduction in glandular trichomes, the present results may suggest a trade‐off between the different trichome types of birch leaves.     

Trichomes and stomata,and their taxonomic significance in theUrticales

Structure and ontogeny of stomata and trichomes have been studied in 23 species and 3 varieties of theUrticales. Stomata are anomocytic, more rarely paracytic; anisocytic and sometimes helicocytic and transitorial types are found inUrticaceae andDorstenia, rarely inArtocarpus. The ontogeny of anomocytic and actinocytic stomata is perigenous, of paracytic either mesogenous or perigenous, of anisocytic either mesogenous or mesoperigenous, and of helicocytic and transitional types mesogenous. Among trichomes eglandular unicellular (wide spread), bicellular or uniseriate filiform (Cannabis); glandular capitate with uni- or bicellular (Moraceae, Ulmaceae, Cannabaceae), uniseriate filiform (Ulmaceae) or multiseriate stalk (Cannabis); sunken glands (Artocarpus); uniseriate glandular with uniseriate stalk (Celtis), and stinging emergences (Urticaceae) have been observed. It is concluded that theUrticales represent a natural order with four families:Ulmaceae, Moraceae, Urticaceae andCannabaceae which are distinct but interrelated with each other.     

国产柿属(Diospyros)的叶表皮形态研究及其分类学意义

为了解柿属(Diospyros)植物的叶表皮特征,在光学显微镜下观察了46种2变种植物的叶表皮微形态特征,并进行了主成分分析。结果表明,柿属植物的叶表皮微形态可分为2组：A组的表皮细胞为不规则形,垂周壁浅波状或深波状;B组的表皮细胞为多边形,垂周壁平直或弓形。气孔全部位于下表皮,以无规则型为主,但同时有辐射型、环列型和十字型气孔存在。大多数种具有表皮毛,表皮毛有非腺毛和头状腺毛的区别。柿属植物的叶表皮微形态特征类型多样,能够为部分类群的分类提供较好的形态学证据。     

Trichome micromorphology in Turkish species of Ziziphora (Lamiaceae)

Ziziphora L. is represented by 5 species and 2 subspecies in the flora of Turkey: Z. clinopodioides, Z. capitata, Z. persica, Z. tenuior, Z. taurica subsp. taurica, Z. taurica subsp. cleonioides. It is difficult to distinguish between some Ziziphora taxa because of their morphological similarities. In this study, the leaf and calyx trichomes of Ziziphora taxa in Turkey were studied in order to assess anatomical variations that may serve as distinguishing characters. Their micromorphological features were surveyed by scanning electron microscopy (SEM) and light microscopy (LM). Trichomes on leaves and calyx can be divided into two general types: non‐glandular trichomes and glandular (secretory) trichomes. The non‐ glandular trichomes are simple, acicular or curved with cuticular micropapillae. They usually consist of one or more additional cells. The glandular trichomes are divided into two types: peltate and capitate and Ziziphora taxa can easily be distinguished by presence/absence, density and types of glandular trichomes on leaves and calyx. The peltate trichomes consist of 12 or 18 secretory head cells in a single disc; four or six central cells surrounded by eight or twelve peripheral ones. Peltate trichomes are absent on the adaxial leaf surface of Z. capitata and Z. persica. Two types of capitate trichomes are present in Ziziphora. The capitate trichomes are only absent on the calyx surface of Z. persica. In addition, the trichome micromorphology provides some support for separating the two subspecies of Z. taurica. In conclusion, Ziziphora taxa can easily be distinguished by cell number, cell shape presence/absence and density of the glandular trichomes on leaves and calyx.     

葛(豆科)叶的解剖学研究

利用光学显微镜和扫描电镜观察了葛(Pueraria lobata)叶的解剖学特征。结果表明,葛叶片的上、下表皮都只有一层表皮细胞,上表皮比下表皮厚。上、下表皮都有腺毛和非腺毛。气孔主要分布在下表皮,下表皮的气孔密度为(261±17)mm-2,上表皮只有(6±3)mm-2。叶肉由两层栅栏组织细胞和一层海绵组织细胞构成。叶肉细胞中有丰富的叶绿体。在栅栏组织和海绵组织之间有一层平行于叶脉的薄壁细胞。叶脉中含有大量的草酸钙晶体。葛叶的这些形态特征与其喜阳、耐旱的特点相适应。     

Comparative Epidermal Ultrastructure of Cotton (Gossypium hirsutum L.) Leaf, Bract and Capsule Wall

Cotton leaves are more physiologically active than the bractand the capsule wall of the fruiting structures. To elucidatethe disparities in their physiological behaviour, epidermalcell density, stomatal index, stomatal size, trichome densityand type, and epicuticular wax ultrastructure of cotton leaf,bract and capsule wall were delineated using scanning electronmicroscopy (SEM). The epidermal cells of the outer periclinalwalls on both surfaces of the leaf and bract were raised andconvex. Conversely, the capsule wall epidermal cells were polygonalwith flat outer periclinal walls. The stomatal complex in theleaf and bract was paracytic, whereas in the capsule wall thestomatal complex was anomocytic. The adaxial and abaxial stomataof the leaf were coplanar to the epidermal surface, as opposedto the raised adaxial stomata on the bract. On the contrary,the stomata on the capsule wall surface appeared to be slightlysunken. Furthermore, the capsule wall stomata were larger thanthe stomata on either surface of both the leaf and the bract.The stomatal index was greater on the abaxial surfaces of theleaf and the bract (18.4 and 9.4, respectively) than their correspondingadaxial surfaces (14.4 and 4.7, respectively). Leaves had thehighest stomatal index followed by the bract and the capsulewall. The indumentum consisted of glandular and nonglandulartrichomes, the density of which was greater on the abaxial surfacesthan on the adaxial surfaces of the leaf and bract. The capsulewall indumentum lacked nonglandular trichomes. Epicuticularwax occurred in the form of striations. However, the striationpattern varied among the organs. This study clearly illustratesmorphological disparities in the epidermal features of leaf,bract and capsule wall, helping to explain their physiologicaldivergence. Copyright 2000 Annals of Botany Company Gossypium hirsutum, epicuticular wax, raised stomata, scanning electron microscopy, stomatal index, trichomes     

Glandular Trichomes on Alfalfa Impede Searching Behavior of the Potato Leafhopper Parasitoid

New cultivars of alfalfa, Medicago sativa L., have been released with glandular trichomes for resistance to potato leafhopper, Empoasca fabae (Harris). Yet, the impact of the glandular trichomes on the primary natural enemy of the leafhopper, Anagrus nigriventris Girault, is unknown. We compared the host searching behavior of the egg parasitoid on four alfalfa clones varying in trichome characters. Female wasps were videotaped on Ranger, a susceptible clone with relatively sparse trichomes, B14, a resistant clone with dense but nonglandular trichomes, and FG12 and FG18, two resistant clones with glandular trichomes. Although the number of leafhopper eggs per stem exposed to wasps did not significantly differ among the four clones, the frequency of foraging and total foraging time were less on the two clones with glandular trichomes than on the two clones with nonglandular trichomes. In addition, an analysis of covariance demonstrated that, although the number of ovipositional probes increased with egg density on a stem, the number of probes on stems with glandular trichomes was significantly less than that on stems without glandular trichomes. The allocation of time by wasps among drumming, probing, and grooming behaviors was similar among the clones. Wasps tended to fly off of clones with glandular trichomes more often than off of clones with nonglandular trichomes. This study suggests that cultivars with glandular trichomes may interfere with host searching by A. nigriventris.     

Glandular trichomes and essential oil constituents ofCalamintha menthifolia (Lamiaceae)

Plant material ofCalamintha menthifolia was collected from two populations grown in the Vikos-Aoos area (NW. Greece). The structure and ontogeny of the glandular trichomes and the chemical composition of the secreted essential oil were studied. The leaves ofC. menthifolia have numerous glandular trichomes of three morphological distinct types: 1) glandular scales with a unicellular foot and stalk, and a 12-celled head, 2) glandular hairs with a unicellular foot and stalk, and a unicellular pear-shaped head and 3) glandular hairs with a unicellular foot, a bicellular stalk and a unicellular elongated head. Qualitative and quantitative GC-MS analyses of the essential oils revealed piperitone oxide as the main constituent in both populations. In the light of these results the relationships beweenC. menthifolia and other members of theSatureja group as well as its taxonomy are discussed.