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.     

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.     

Evolution of trichomes and its systematic significance in Salvia (Mentheae; Nepetoideae; Lamiaceae)

We have investigated the trichome characteristics in representative species of Salvia and Pleudia in order to evaluate this source of morphological evidence for addressing problems regarding generic delimitation and subgeneric classification. Trichomes of 46 Salvia spp., representing three subgenera in Iran, were investigated using light microscopy and scanning electron microscopy. General trichome characteristics were constant among different populations of a certain species, but showed a degree of variability useful in the delimitation of taxa, specifically at lower taxonomic levels. Trichome characters of taxonomic interest are as follows: types of glandular hair; number of composing cells (uni‐, bi‐ or multicellular); size and thickness; branching pattern; and presence of papillae on the surface. Non‐glandular trichomes can be simple and branched. Glandular trichomes can be stalked, subsessile or sessile. Our investigation reveals the usefulness of such characters in providing fundamental taxonomic criteria for taxon delimitation in these genera at various levels, especially at the specific rank. Furthermore, the data presented here indicate the potential applicability of such characters in the determination of evolutionary trends in Salvia and allies. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 241–257.     

Taxonomical significance of the leaf indument inDryopteris (Pteridophyta): I. Some North American,Macaronesian and European taxa

The leaf indument of a number of North American, Macaronesian and EuropeanDryopteris taxa is described. Trichome characters provide very useful taxonomical data for the study of species complexes and for tracing relationships among geographically isolated or separated taxa. The new combination,D. expansa var.alpina, is made. The present study sustains best theWagner D. semicristata relationship scheme.     

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.     

A landscape of hairy and twisted: hunting for new trichome mutants in the Saskatoon Arabidopsis T‐DNA population

A total of 88 new Arabidopsis lines with trichome variation were recovered by screening 49,200 single‐seed descent T₃ lines from the SK activation‐tagged population and from a new 20,000‐line T‐DNA insertion population (called pAG). Trichome variant lines were classified into 12 distinct phenotype categories. Single or multiple T‐DNA insertion sites were identified for 89% of these mutant lines. Alleles of the well‐known trichome genes TRY, GL2 and TTG1 were recovered with atypical phenotype variation not reported previously. Moreover, atypical gene expression profiles were documented for two additional mutants specifying TRY and GL2 disruptions. In remaining mutants, ten lines were disrupted in genes coding for proteins not implicated in trichome development, five were disrupted in hypothetical proteins and 11 were disrupted in proteins with unknown function. The collection represents new opportunities for the plant biology community to define trichome development more precisely and to refine the function of individual trichome genes.     

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.     

Comparative analysis of micromorphological characters in two distantly related Mexican oaks, Quercus conzattii and Q. eduardii (Fagaceae), and their hybrids

Interspecific hybridization occurs with high frequency in the genusQuercus, but few studies have analyzed and compared micromorphological characters in putative parental species and their hybrids.Quercus eduardii andQ. conzattii are two Mexican black oak species that, although distantly related, have formed at least one population of hybrid origin, where individuals with intermediate macromorphology are present. The purpose of this investigation was to analyze the degree of differentiation in micromorphological characters between the two species and to assess the expression of these characters in individuals with intermediate macromorphology. Foliar trichomes, epicuticular waxes, stomata, and pollen grains, were examined using scanning electron microscopy (SEM) in the three types of individuals (Q. conzatti, Q. eduardii, and intermediates). Trichome density was quantified with light microscopy. Types of trichomes present, length of trichome arms, types of epicuticular wax on the leaf surfaces, and the position of stomata with respect to the foliar surface were characters useful to differentiate betweenQ. conzattii andQ. eduardii. Plants with intermediate macromorphology displayed a pattern of micromorphological characters that were identical to one parental species (Q. conzattii), or extreme or novel relative to both species.     

Cost of trichome production and resistance to a specialist insect herbivore in <Emphasis Type="Italic">Arabidopsis lyrata</Emphasis>

Theory predicts that trade-offs between resistance to herbivory and other traits positively affecting fitness can maintain genetic variation in resistance within plant populations. In the perennial herb Arabidopsis lyrata, trichome production is a resistance trait that exhibits both qualitative and quantitative variation. Using a paternal half-sib design, we conducted two greenhouse experiments to ask whether trichomes confer resistance to oviposition and leaf herbivory by the specialist moth Plutella xylostella, and to examine potential genetic constraints on evolution of increased resistance and trichome density. In addition, we examined whether trichome production is induced by insect herbivory. We found strong positive genetic and phenotypic correlations between leaf trichome density and resistance to leaf herbivory, demonstrating that the production of leaf trichomes increases resistance to leaf damage by P. xylostella. Also resistance to oviposition tended to increase with increasing leaf trichome density, but genetic and phenotypic correlations were not statistically significant. Trichome density and resistance to leaf herbivory were negatively correlated genetically with plant size in the absence of herbivores, but not in the presence of herbivores. There was no evidence of increased trichome production after leaf damage by P. xylostella. The results suggest that trichome production and resistance to leaf herbivory are associated with a cost and that the direction of selection on resistance and trichome density depends on the intensity of herbivory.     

Evidence of Three Subspecies in Trifolium nigrescens Viv.

Germplasm accessions of Trifolium nigrescens Viv. were foundto belong to three distinct taxa which differed in morphology,hybrid seed-set in crosses among themselves and with white clover(T. repens L.), chromosomal distribution of rDNA genes, andrDNA internally transcribed spacer (ITS) region sequences. Thesetaxonomic groups correspond with T. nigrescens ssp. nigrescens,T. nigrescens ssp. petrisavii var.petrisavii and var. meneghinianum.The existence of var. meneghinianum has been rejected or ignoredin recent taxonomic treatments. The present study indicatesthat it is very distinctive and warrants at least subspeciesstatus. Phylogenetic analysis based on ITS sequences and podmorphology placed ssp. nigrescens as progenitor to the others.ITS sequences placed white clover closer to ssp. petrisaviibut neither DNA sequences nor rDNA chromosome locations clearlyshowed whether var. petrisavii or var. meneghinianum was closerto white clover. In contrast, results of hybridization studiesshowed that ssp. nigrescens gave full seed-set when pollinatedwith T. repens whereas both ssp. petrisavii var. petrisaviiand ssp. petrisavii var. meneghinianum gave poor seed-set. Allthree taxa showed close relationships with white clover andnone can clearly be shown to be a direct ancestor of T. repens.Copyright 2001 Annals of Botany Company Fabaceae, Trifolium nigrescens, Trifolium repens, internal transcribed spacer region (ITS), nuclear ribosomal DNA, interspecific hybridization     

Artificial Defoliation Induces Trichome Production in the Tropical Shrub Cnidoscolus aconitifolius (Euphorbiaceae)1

Induction of plant defenses and their spatial variability are key subjects in the field of ecology and evolution of defensive traits in plants. Nevertheless, induction has been more commonly studied under controlled environments, ignoring other factors that might influence this process in natural settings. The main goal of this study was to determine if artificial defoliation induces trichome production in three natural populations of the tropical shrub Cnidoscolus aconitifolius. First, we performed trichome counts for each population before imposing artificial defoliation to assess differences in trichome loads between populations. Trichome densities (trichomes/cm²) were quantified for leaf blades, petioles, and flower stalks. To determine if defoliation induced trichome production, three defoliation treatments (0% leaves defoliated or controls, 50% of total leaves defoliated, and 100% defoliation) were applied once at the beginning of the reproductive season. Trichome counts were performed on each structure every ～20 d during a 3‐mo period after the application of treatments. Trichome counts showed significant differences in trichome densities between populations for all three structures. In turn, artificial defoliation increased trichome density. Significant differences among treatments were found for trichome densities on leaf blades and petioles. In both these structures, the 100 percent defoliation treatment differed significantly from control plants, presenting higher trichome densities. In addition, the treatment × population interaction was not significant for leaf blades and petioles, indicating that induction is a generalized response in this species, at least at the study sites. These results indicate that trichomes in C. aconitifolius are inducible due to defoliation.     

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.     

Taxonomic Study of Linaria depauperata and L. supina Complexes in Eastern Spain

Morphological characteristics were studied in two groups ofclosely related taxa of sectionSupinae , Linaria depauperataand L. supina, from eastern Spain. Vegetative, floral and seedcharacteristics were of little use in distinguishing betweenthese taxa as the ranges for all the taxa studied overlapped.Flower colour could be used as a diagnostic character for somebut not all of these taxa. Seed coat characters were of hightaxonomic value, both when trying to distinguish among thesetwo groups, and the taxa included within them, and also whenestablishing relationships among the taxa studied. Some differenceswere found in the indumentum distribution and density. Threetypes of trichomes were identified, two of them eglandular andcommon to all taxa. The third type of trichome was a simplegland, that varied in the number of cells in the stalk and gland.Trichome length and wall width of stalk cells allowed severalgroups of taxa to be distinguished. Similarity relationshipsamong the samples studied are shown in a UPGMA phenogram. Accordingto these results, two new species, L. cardonica and L. sulphurea,are described. L. arabiniana is conspecific with L. depauperatasubsp. hegelmaieri. A key to identify the different taxa isprovided. Copyright 2001 Annals of Botany Company Scropulariaceae, Antirrhineae, taxonomy, morphological characters, seed-coat, trichomes, Linaria depauperata,Linaria supina     

Evaluation of seed and leaf epidermis characters in the taxonomy of some annual species of the genus Papaver (Papaveraceae)

To get a better understanding of their taxonomic importance, we examined morphological, leaf epidermal and seed micromorphological characters of 19 taxa of annual Papaver L. belonging to the sections Papaver, Carinatae Fedde and Rhoeadium Spach. Among the studied taxa, the pattern of the coat of the seed testa cells and seed epidermal cell showed large variation. The granulate type of testa sculpturing was most common, but other types were represented by one or two species. In contrast, most of the taxa have broadly similar leaf epidermal characteristics. We conclude that variation in seed characters are significant for the taxonomy at the specific and generic levels, whereas leaf epidermis morphology, with few exceptions, is mostly only useful for separation of taxa within species. Based on the results, P. lacerum Popov is regarded as a synonym of P. commutatum Fisch. & C. A. Mey, while P. piptostigma Bienert ex Fedde, P. halophilum (Fedde) Cullen and P. tubuliferum Fedde are regarded as synonyms of P. macrostomum Boiss. et Huet ex Boiss. var. macrostomum. Further, Papaver gaubae Cullen & Rech. f. and P. bipinnatum C. A. Mey. are included into the synonymy list of P. glaucum Boiss. et Hausskn. and P. arenarium M.‐Bieb., respectively. In contrast, Papaver chelidoniifolium Fisch. & C. A. Mey. var. pinnatum Tavakkoli & Assadi from Gilan province is described as a new variety, and P. rhoeas L. var. strigosum Boenn. and var. glabrum Fedde and P. commutatum subsp. euxinum Kadereit are introduced as new records to Iran. The evolutionary and phylogenetic implications of the observed variation in seed characteristics are also discussed.     

Distinction in morphology and esterase isozyme betweenEupatorium glehni (=E. chinense subsp.sachalinense) andE. chinense var.oppositifolium (compositae)

The taxonomic status ofEupatorium chinese var.oppositofolium andE. glehni (=E. chinense subsp.sachalinense) inE. chinense complex semsu Kitamura has long been controversial. In this paper, the degree of divergence between diploids of these two taxa was examined by means of morphological studies including principal component analysis, the electrophoretic analysis of esterase isozyme variation and observations on habitats. The data obtained through the examinations indicate these two taxa are diverged enough to be recognized as distinct biological species. Since the polyploidE. chinense var.oppositifolium is more or less intermediate in morphology between the two diploid taxa, it is considered to have masked the distinction between the two diploid taxa. Also, electrophoretic evidence suggests that polyploidE. chinense var.oppositifolium is not a hybrid or hybrid derivative withE. glehni as a parental species. Possible origin of polyploidE. chinense varoppositifolium is also discussed.     

Hair morphology and systematics ofPhysalis (Solanaceae)

Hair morphology was exammed on developing seedlings and mature plants of ten species from five of seven series inPhysalis. The taxonomic importance of hair development and the distribution of hair types then was evaluated with respect to other comparative data. Two classes of hair types were observed, as found in earlier investigations ofSolanum andRhododendron. The first hair class comprises a sequence from unbranched hairs to dendroid-stelliform hairs. Hairs of this class show considerable variability among taxa in size, presence or absence of glandular tips, and presence and degree of branching, and so were useful in making taxonomic comparisons. The second hair class consists of short hairs, each tipped with a multicellular gland. This second hair class was not useful taxonomically because of its lack of variability in morphology and its often rare occurrence on a plant. The taxa studied exhibit distinctive trichome features which serve to distinguish series and, in some cases together with other data, provided new insight into previously enigmatic species relationships.     

Ants,Stem Borers,and Pubescence in Endospermum in Papua New Guinea1

The stems of the ant-plant, Endospermum labios Schodde, serve as colonization sites for the ant, Camponotus quadriceps F. Smith. They are also subject to damage by insect borers. We sampled young E. labios trees in distutbed forest to compare evidence of stem boring insect and stem miner damage in plants with and without colonies of C. quadriceps. Dissections of a subsample of plants showed that dipteran stem borers and stem miner damage were significantly more common in plants lacking C, quadriceps colonies than in plants with established colonies. Evidence from these dissections and from field counts of meristem damage caused by emerging borers suggested that coleopteran stem borers were also more abundant when ants were not present. In addition to the incidence of stem boring insects and ant colonies, we examined relative levels of leaf pubescence by measuring trichome density and leaf size for E. labios trees. We found that trichome density was significantly greater in trees with evidence of prior shoot damage (presumably from stem borer emergence at the meristem) but was not significantly related to the presence or absence of an ant colony. This prompted us to compare trichome density on leaves of nearby small trees and of different branches of the same tree, pairing a stem/branch that appeared damaged with one that appeared healthy. Trichome densities on leaves from damaged stems and branches were significantly greater than were trichome densities on healthy branches and stems. Based on these empirical data, we present several possible explanations for the patterns of association between ants, stem borers, and pubescence. Although feeding preference tests with a common folivore showed no effect of trichome densities on leaves, we suggest further study on how trichomes may affect ovipositing stem borers.