Evolution of trichome types and its systematic significance in the genus Phlomoides (Lamioideae–Lamiaceae)

Despite a number of recent molecular phylogenetic studies on Phlomoides, in terms of trichome morphology the genus is still among the most poorly studied taxa in the family Lamiaceae. In order to test the utility of trichome characters for delimitation of sections, subsection and species of Phlomoides, we examined trichomes of 64 species representing all recognized sections and subsections using stereomicroscopy and scaning electron microscopy. Two basic types of trichomes could be identified: non‐glandular and glandular. Both trichome types can be simple or branched. The glandular trichomes were sessile, short stalked or long stalked. Different kinds of branched trichomes were observed in most species of P. sect. Phlomoides, i.e. symmetrically stellate, stellate with a central long branch, bi‐ or trifurcate. The species of P. sect. Filipendula were mostly covered by simple trichomes. Moreover, variation in trichome characters appears to have particular value, not only for the classification at sectional or subsectional rank, but also for delimitation of species within each section. For example, all studied species of P. subsect. Fulgentes are characterized by various kinds of stellate trichomes, while the trichome variability in P. subsect. Tetragonae was sufficiently high for species discrimination. An ancestral character state reconstruction was performed in order to investigate the evolution of trichome types and it revealed the following evolutionary trends in trichome characters of Phlomoides: 1) branched trichomes are primitive in Phlomoides as compared to simple ones, 2) long simple non‐glandular trichomes are derived as compared to short simple ones and 3) the presence of stalked glandular trichomes is advanced as compared to subsessile or sessile ones.     

Trichome micromorphology of Iranian Stachys (Lamiaceae) with emphasis on its systematic implication

Trichomes of 37 taxa of the genus Stachys and one species of Sideritis (S. montana) were examined using light and scanning electron microscopy. The indumentum shows considerable variability among different species, but is constant among different populations of one species, and therefore, affords valuable characters in delimitation of sections and species. The characters of taxonomic interest were presence of glandular and non-glandular trichomes, thickness of the cell walls, number of cells (unicellular or multi-cellular), presence of branched (dendroid) trichomes, presence of vermiform trichomes, orientation of trichomes in relation to the epidermal surface, curviness of trichomes, and presence of papillae on trichome surface. Two basic types of trichomes can be distinguished: glandular and non-glandular trichomes. The glandular trichomes can in turn be subdivided into subtypes: stalked, subsessile, or sessile. The stalks of the glandular trichomes can be uni- or multi-cellular. Simple unbranched and branched trichomes constitute two subtypes of non-glandular trichomes. Our data do not provide any support for separation of Sideritis from Stachys. The following evolutionary trends are suggested here for Stachys: vermiform trichomes with stellate base are primitive against vermiform trichomes with tuberculate base, long vermiform trichomes are primitive against the short simple trichomes, appressed trichomes are advanced against spreading ones, and loss of glandular trichomes is advanced against their presence. Overall, trichome micromorphology is more useful in separation of species within sections rather than characterizing large natural groups known as sections, except for few cases.     

Trichome micromorphology of the Chinese-Himalayan genus <Emphasis Type="Italic">Colquhounia</Emphasis> (Lamiaceae), with emphasis on taxonomic implications

Trichome micromorphology of leaves and young stems of nine taxa (including four varieties) of Colquhounia were examined using light and scanning microscopy. Two basic types of trichomes were recognized: eglandular and glandular. Eglandular trichomes are subdivided into simple and branched trichomes. Based on the number of cells and trichome configuration, simple eglandular trichomes are further divided into four forms: unicellular, two-celled, three-celled and more than three-celled trichomes. Based on branching configuration, the branched eglandular trichomes can be separated into three forms: biramous, stellate and dendroid. Glandular trichomes can be divided into two subtypes: capitate and peltate glandular trichomes. Results from this study of morphological diversity of trichomes within Colquhounia lend insight into infrageneric classification and species relationships. Based on the presence of branched trichomes in C. elegans, this species should be transferred from Colquhounia sect. Simplicipili to sect. Colquhounia. We provide a taxonomic key to species of Chinese Colquhounia based on trichome morphology and other important morphological traits.     

Trichome micromorphology in Alcea L. and allied genera (Malvaceae) and its systematic implication

Trichomes of 26 species of Alcea (Malvaceae) were investigated using light (LM) and scanning electron microscopy (SEM). The trichomes show a great micromorphological variation, which provides data useful for species delimitation in Alcea. Two basic types of trichomes could be distinguished in Alcea and allied genera: glandular and eglandular. The glandular trichomes could in turn be subdivided into two subtypes: capitate and clavate. The eglandular trichomes could be subdivided into five subtypes: simple, fascicled, stellate, fascicled-stellate and pluri-radiate. Characters of taxonomic interest are: trichome density (glabrous to dense), number of arms per trichome, orientation relative to the epidermal surface (appressed to erect) and presence/absence of a stalk. According to the results the species of Alcea can be divided into four informal groups based on trichome types. The results further support the exclusion of the annual Althaea species from the perennial ones and their close relationship to Malva. In addition, a close relationship between perennial Althaea and basal Alcea lineages is supported. Based on the evolutionary framework provided by recent molecular phylogenetic investigations, the following trends can be observed in the Malva alliance: long and narrow-armed trichomes are primitive in relation to short and thick-armed trichomes; dense indumentum coverage is primitive in relation to moderately dense or glabrous ones; presence of simple hairs on stem (particularly on leaves) is more advanced than their absence; spreading villous-stellate and fascicled trichomes are more advanced than appressed stellate ones. Clavate trichomes, which were found exclusively in a few species of Alcea, should be considered as a derived state in relation to capitate ones, and they may provide a synapomorphy for the crown group of Alcea.     

Glandular Trichomes ofCalceolaria adscendensLidl. (Scrophulariaceae): Histochemistry,Development and Ultrastructure

This paper reports the results of a study of the morphology and development of glandular trichomes in leaves ofCalceolaria adscendensLidl. using light and electron microscopy. Secretory trichomes started as outgrowths of epidermal cells; subsequent divisions gave rise to trichomes made up of a basal epidermal cell, a stalk cell and a two-celled secretory head. Ultrastructural characteristics of trichome cells were typical of terpene-producing structures. Previous phytochemical studies had revealed thatC. adscendensproduces diterpenes. Comparison withC. volckmanni,which produces triterpenes, and has trichomes with eight-celled secretory heads, suggests that there could be a relationship between the type of glandular trichome and the class of terpene produced. Further work is needed to test the hypothesis and to develop trichome characters as taxonomic tools.     

七彩红竹中类黄酮-3-O-葡萄糖基转移酶基因的克隆及功能分析

类黄酮-3-O-葡萄糖基转移酶(Flavonoid-3-O-glucosyltransferase,3GT)是花青苷(Anthocyanins)生物合成途径中的关键酶,它主要负责将不稳定的花色素转变为稳定的花色素苷,虽然目前已经从其他植物中克隆获得类黄酮-3-O-葡萄糖基转移酶,但是对竹子中的类黄酮-3-O-葡萄糖基转移酶并不清楚。该文以产生花青素的七彩红竹(Indosasa hispida Mc Clure cv.Rainbow)为材料,首先通过3GT的同源比对后设计3GT基因特异引物,获得3GT基因片段;然后运用RT-PCR及RACE技术从七彩红竹茎中克隆得到完整的3GT基因(Ih3GT)。结果表明:Ih3GT基因的c DNA全长序列为1 730 bp,含有1个1 425 bp的开放阅读框(ORF),编码474个氨基酸;系统进化分析显示,七彩红竹3GT与其他禾本科植物的3GT聚类到同一个分支;该基因推断的蛋白与水稻(Oryza sativa)3GT蛋白的相似性为69%,与二穗短柄草(Brachypodium distachyon)3GT的相似性为67%;经氨基酸序列比对,推断七彩红竹3GT含有糖基转移酶基因家族特有的结构域PSPG-box;半定量PCR的结果显示,七彩红竹3GT基因在微红的幼茎中大量表达,而在其他组织中并不表达,说明Ih3GT具有组织表达特异性。该结果为今后深入研究七彩红竹花色苷的形成机理、鉴定Ih3GT酶活性以及利用Ih3GT基因培育竹子新品种奠定了基础。     

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.     

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.     

Foliar appendages in certain species ofSalvia (studies inLamiaceae VI)

Foliar appendages of eight species ofSalvia L. have been studied. Eleven types of non glandular and five types of glandular appendages have been observed. They have been classified under three major categories: (1) glandular capitate; (2) non glandular filiform and (3) non glandular capitate. Five new types of trichomes have been reported fromLamiaceae for the first time. On the basis of trichome types different species ofSalvia can be identified. A tentative key has been presented.     

Ultra-sculpturing of seed morphotypes in selected species of genus Salvia L. and their taxonomic significance

• The taxonomic importance of macromorphological and micromorphological seed characteristics was investigated using SEM of ten species of the Salvia genus from Pakistan. The aim was to identify diagnostic seed ultrastructural features that could aid in species delimitation, correct identification and phylogenetic position. The ultrastructure of Salvia varies greatly, and a wide range of unique micromorphological features have been observed.
• Seed micromorphological features were explored by SEM, including seed shape, colour, texture, cell outline, surface sculpturing, epidermal cell arrangement, anticlinal, and periclinal wall pattern.
• Seed shapes were categorized as obovate, spherical, spheroid, broadly elliptic, elliptic and oblong, mostly with a terminal hilum. Seed colours were black, light brown, dark brown, brown and yellow. Exo-morphological characters, i.e. epidermal cell arrangements, included irregular, wavy pentagonal-hexagonal, regular pentagonal-hexagonal. Cluster analysis was used to assess similar and distinct species within Salvia with a feasible explanation. Taxonomic keys were made based on micromorphological qualitative features that help to delimit species and identify them quickly within the Salvia genus.
• Seed morphology of ten Salvia species was described and investigated, and the diagnostic significance of features evaluated using SEM. This study analysed seed features, especially at the species level, which might provide much new taxonomic information. The results revealed that, in seed morphology, using SEM can help with taxon identification, especially at the genus and species levels.

     

Taxonomic importance of seed macro‐ and micro‐morphology in Abelmoschus (Malvaceae)

Seed morphology of Abelmoschus is known to be variable, but patterns of variation have never been critically studied. We studied seed macro‐ and micro‐morphological characters, including seed shape/size, seed coat pattern and trichome density/structure in multiple samples to evaluate the taxonomic significance of seed characters. Among the studied characters, seed shape and trichome structure were found to have major taxonomic importance and proved to be valuable characters for separating taxa. Two main seed types were present: seeds with deciduous trichomes and seeds with persistent trichomes. These characters offer significant evidence to the distinctness of certain species (A. esculentus, A. moschatus subsp. moschatus, A. moschatus subsp. tuberosus, A. crinitus and A. angulosus). Further, our results indicate that A. moschatus subsp. tuberosus should be maintained as a separate subspecies while A. manihot subsp. tetraphyllus var. pungens may be merged in A. angulosus. No significant intraspecific variation was observed, except in A. esculentus. We conclude that seed coat sculpturing and seed trichomes do indeed provide stable and diagnostic characters for many morphologically closely related taxa of Abelmoschus and that LM/SEM techniques can be useful in solving systematic problems and management of Abelmoschus genetic resources.     

Seed and trichome morphology of the Egyptian Fagonia (Zygophyllaceae) with emphasis on their systematic implications

Seed and trichome morphology of 13 taxa representing the genus Fagonia in Egypt have been studied using light (LM) and scanning electron microscopy (SEM). Macro‐ and micro‐morphological characters, including seed shape, seed size, seed coat sculpture, trichome density and structure were studied to evaluate their systematic significance. Seed shape and trichome density were found to have only minor taxonomic value, but seed coat sculpturing and trichome structure proved to be valuable characters. These characters offer evidence to combine certain species, e.g. Fagonia kassasii and F. schimperi in F. bruguieri, Fagonia microphylla in F. scabra and Fagonia thebaica in F. arabica. However, F. sinaica, F. tristis, F. boveana and F. isotricha should be maintained as separate species. Generally, the different patterns of seed and trichome morphology are useful in delimitation of species within the genus Fagonia, but they could not be used to characterize groups of related species.     

Glandular trichomes as a barrier against atmospheric oxidative stress: Relationships with ozone uptake,leaf damage,and emission of LOX products across a diverse set of species

There is a spectacular variability in trichome types and densities and trichome metabolites across species, but the functional implications of this variability in protecting from atmospheric oxidative stresses remain poorly understood. The aim of this study was to evaluate the possible protective role of glandular and non‐glandular trichomes against ozone stress. We investigated the interspecific variation in types and density of trichomes and how these traits were associated with elevated ozone impacts on visible leaf damage, net assimilation rate, stomatal conductance, chlorophyll fluorescence, and emissions of lipoxygenase pathway products in 24 species with widely varying trichome characteristics and taxonomy. Both peltate and capitate glandular trichomes played a critical role in reducing leaf ozone uptake, but no impact of non‐glandular trichomes was observed. Across species, the visible ozone damage varied 10.1‐fold, reduction in net assimilation rate 3.3‐fold, and release of lipoxygenase compounds 14.4‐fold, and species with lower glandular trichome density were more sensitive to ozone stress and more vulnerable to ozone damage compared to species with high glandular trichome density. These results demonstrate that leaf surface glandular trichomes constitute a major factor in reducing ozone toxicity and function as a chemical barrier that neutralizes the ozone before it enters the leaf.     

Trichome micromorphology of the East Asiatic genus Chelonopsis (Lamiaceae) and its systematic implications

The micromorphology of trichomes of the leaves of 17 taxa (including two varieties) of the genus Chelonopsis Miq. and of six species representing four additional genera (Bostrychanthera deflexa Benth., Colquhounia coccinea Wall. var. coccinea, Co. seguinii Vaniot. var. seguinii, Gomphostemma chinense Oliv. var. chinense, G. crinitum Wall. ex Benth. and Physostegia virginiana (L.) Benth.) was surveyed by light and scanning electron microscopy. Two basic types of trichomes can be identified: non-glandular and glandular trichomes. The non-glandular trichomes can be subdivided into two subtypes: simple unbranched and branched trichomes. Based on the cell number, simple unbranched trichomes are further divided into four shapes (unicellular, two-celled, three-celled, and more than three cells), whilst branched trichomes are separated into three shapes (biramous, stellate, and dendroid trichomes). The glandular trichomes can in turn be subdivided into four subtypes: subsessile, capitate, clavate, and sunken. Non-glandular trichomes with two cells (NGTW) and subsessile glandular trichomes (GSU) are most widespread in all taxa examined. The indumentum shows considerable variation among different sections or species. Consequently, trichome micromorphology and distribution have high taxonomic value for Chelonopsis at both infrageneric and interspecific levels. The presence of capitate glandular trichomes (GCA) provides an additional morphological character to clarify the boundaries between subgenus Chelonopsis and Aequidens Wu and Li. Within subgenus Aequidens, non-glandular trichomes with more than three cells (NGMT) and clavate glandular trichomes (GCL) are important characters for sectional division between sect. Aequidens Wu and Li and sect. Microphyllum Wu and Li. Again, three forms of three-celled trichomes can be used as a distinctive taxonomic character at specific level between C. albiflora Pax et K. Hoffm. ex Limpr., C. forrestii J. Anthony, and C. souliei (Bonati) Merr. in sect. Aequidens. This study supports Wu's delimitation of subgenus and sections and the subsequent review work by Xiang et al. Additionally, distribution of trichome types is correlated with the altitudinal distribution and habitats of some species in Chelonopsis.     

The taxonomic utility of micromorphology in Lepidaploa (Vernonieae: Asteraceae)

Lepidaploa belongs to tribe Vernonieae, one of the most complex tribes of Asteraceae, and the relationships within Lepidaploa and among related genera are poorly understood. Microcharacters may be of taxonomic value and may be used in the identification of taxa at different ranks. To evaluate the reliability of microcharacters as taxonomic markers in this group, we analysed the micromorphology of phyllaries, florets and cypselae in detail in 23 species of Lepidaploa .The species were studied using stereo, light, and scanning electron microscopy. Eight trichome types (eglandular and glandular) were observed on phyllaries, florets and cypselae, in addition to crystals, idioblasts and other microstructures. The results demonstrates that the ocurrence of different combinations of trichome types and crystals, presence of a stylar basal node, idioblasts and glandular apical anther appendages are highly useful to differentiate between related species of Lepidaploa and a diagnostic key using these characters is presented. However, these characters are not of much use to distinguish between closely related genera of Vernonieae since most characters appear homeoplasic and are found in representatives of different genera.