Foliar Trichomes Research Articles

Foliar trichomes, boundary layers, and gas exchange in 12 species of epiphytic Tillandsia (Bromeliaceae)

We examined the relationships between H2O and CO2 gas exchange parameters and leaf trichome cover in 12 species of Tillandsia that exhibit a wide range in trichome size and trichome cover. Previous investigations have hypothesized that trichomes function to enhance boundary layers around Tillandsioid leaves thereby buffering the evaporative demand of the atmosphere and retarding transpirational water loss. Data presented herein suggest that trichome-enhanced boundary layers have negligible effects on Tillandsia gas exchange, as indicated by the lack of statistically significant relationships in regression analyses of gas exchange parameters and trichome cover. We calculated trichome and leaf boundary layer components, and their associated effects on H2O and CO2 gas exchange. The results further indicate trichome-enhanced boundary layers do not significantly reduce transpirational water loss. We conclude that although the trichomes undoubtedly increase the thickness of the boundary layer, the increase due to Tillandsioid trichomes is inconsequential in terms of whole leaf boundary layers, and any associated reduction in transpirational water loss is also negligible within the whole plant gas exchange pathway.

Branched Foliar Trichomes of Lobelioideae (Campanulaceae) and the Infrageneric Classification of Centropogon

The morphology of branched foliar trichomes in Lobelioideae (Campanulaceae) was studied via scanning electron microscopy. Trichomes of this type are found only in the Neotropical endemics Burmeistera, Centropogon, and Siphocampylus, and in the Hawaiian endemic Cyanea. The 37 species examined included all species with branched trichomes in Burmeistera, Centropogon sect. Burmeisteroides, Centropogon sect. Niveopsis, Centropogon sect. Wimmeriopsis, Cyanea, and Siphocampylus, plus about one- fourth of the 100 species comprising Centropogon sect. Siphocampyloides. Trichomes observed conformed to eight structural types. Dendritic, multangulate, multangulate-dendritic, echinoid, and furcate hairs were found only in Centropogon sect. Siphocampyloides, Cyanea, and Siphocampylus. Echinoid-dendritic hairs were confined to Centropogon sect. Burmeisteroides, stellate hairs to Centropogon sect. Wimmeriopsis, and multiseriate- multangulate hairs to Burmeistera and Centropogon sect. Niveopsis. Within Centropogon, the distribution of trichome types is consistent with the currently accepted classification of the genus. Correlations with other data, both morphological and molecular, suggest that branched trichomes have evolved in the subfamily repeatedly, perhaps as many as 11 times.

Estimativa de parâmetros genéticos e correlação entre componentes de resistência à traça-do-tomateiro em progênies de Lycopersicon esculentum x L. hirsutum f. glabratum

Avaliou-se o comportamento de cinco progênies F3 do cruzamento entre Lycopersicon esculentum cv. IPA-6 e L. hirsutum f. glabratum PI 134418, quanto ao ataque da traça-do-tomateiro, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), com base na determinação dos parâmetros genéticos e nas correlações entre componentes de resistência. Foi avaliada a área foliar danificada por T. absoluta, em cm²; o número de tricomas tipo VI, por mm², nas faces adaxial e abaxial; e o número de galerias por folíolo. As seleções utilizando-se os parâmetros área foliar danificada, número de tricomas tipo VI das faces adaxial e abaxial das folhas e número de galerias de T. absoluta têm grandes possibilidades de proporcionarem ganhos genéticos futuros, por apresentarem ampla variabilidade genotípica, com valores elevados de coeficiente de determinação genotípica e magnitude superior à unidade para o índice de variação. As correlações fenotípicas entre a área foliar consumida por T. absoluta e as densidades de tricomas das faces adaxial e abaxial das folhas foram negativas e significativas, assim como entre a área foliar e o número de galerias feitas pela T. absoluta por folíolo. Também verificaram-se correlações significativas e positivas para as densidades de tricomas nas duas faces foliares. Isso indica que a resistência está diretamente relacionada a maiores quantidades de tricomas foliares do tipo VI, e ainda que genótipos com valores de DANO alto possuam menor número de galerias.

Amino acid uptake and profile in bromeliads with different habits cultivated in vitro

Bromeliads can have terrestrial and epiphytic habits. Therefore, they have developed probably different mechanisms for the uptake of nutrients from distinct sources such as the pedosphere and the atmosphere. Many bromeliads, such as the epiphytes, absorb water and nutrients almost exclusively via their foliar trichomes. In contrast, terrestrial bromeliads essentially use their roots to withdraw the nutrients from the soil. The aim of this study was to compare nitrogen (N) nutrition between a terrestrial, Ananas comosus (L.) Merr., and an epiphytic, Vriesea gigantea Gaudich., bromeliad. The in vitro absorption of [ 3H]glycine and [ 3H]glutamine was investigated. Plants were also grown in vitro with NH 4 +, glutamine (Gln) or glycine (Gly) as N sources, and the amino acid profile was analyzed. Ammonium treatment had little effect upon the A. comosus amino acid profile, while asparagine was the main amino acid accumulated in V. gigantea after 3 d in a medium with this nitrogen source. This suggests that V. gigantea accumulate N in compounds with high N/C ratio, allowing it to store higher N level when it is available in epiphytic environment. The two species were able to take up amino acids in vitro, although V. gigantea had a higher rate of amino acid uptake than the terrestrial bromeliad, A. comosus. For both species, Gly was taken up in a higher rate than Gln. The data support the idea that V. gigantea has a luxury consumption when inorganic and organic N are available in the environment, which does not happen in the case of the terrestrial bromeliad A. comosus. It has a more stable source of nutrients, the soil. We can also suggest that amino acids such as Gly, Gln and others present in the bromeliad tank water may be important N sources for V. gigantea and other epiphytic bromeliads in natural habitats.

Leaf anatomy and foliar trichomes in Heliotropiaceae and their systematic relevance

Summary Leaf anatomy and the distribution of foliar trichome types of 65 species of Heliotropiaceae have been investigated. The aim was to evaluate the systematic relevance of their diversity as compared to recent findings of systematic relationships within the family. The results of leaf anatomy patterns, especially venation, vascular system, various foliar trichome types, and localization of crystals are of surprisingly high systematic value and prove the actual proposed subdivision of this family based on molecular results. Each main clade identified in the molecular studies is well characterized on the basis of leaf anatomy.

The role of CAM in high rainfall cloud forests: an in situ comparison of photosynthetic pathways in Bromeliaceae

AbstractCrassulacean acid metabolism (CAM), an advanced photosynthetic pathway conferring water conservation to plants in arid habitats, has enigmatically been reported in some species restricted to extremely wet tropical forests. Of these, epiphytic Bromeliaceae may possess absorbent foliar trichomes that hinder gas‐exchange when wetted, imposing further limitations on carbon dioxide (CO2) uptake. The hypothesis that the metabolic plasticity inherent to CAM confers an ecological advantage over conventional C3 plants, when constant rainfall and mist might inhibit gas‐exchange was investigated. Gas‐exchange, fluorometry and organic acid and mineral nutrient contents were compared for the bromeliads Aechmea dactylina (CAM) and Werauhia capitata (C3) in situ at the Cerro Jefe cloud forest, Panama (annual rainfall > 4 m). Daily carbon gain and photosynthetic nutrient use efficiencies were consistently higher for A. dactylina, due to a greater CO2 uptake period, recycling of CO2 from respiration and a dynamic response of CO2 uptake to wetting of leaf surfaces. During the dry season CAM also had water conserving and photoprotective roles. A paucity of CAM species at Cerro Jefe suggests a recent radiation of this photosynthetic pathway into the wet cloud forest, with CAM extending diversity in form and function for epiphytes.

Hydrophobic trichome layers and epicuticular wax powders in Bromeliaceae

The distinctive foliar trichome of Bromeliaceae has promoted the evolution of an epiphytic habit in certain taxa by allowing the shoot to assume a significant role in the uptake of water and mineral nutrients. Despite the profound ecophysiological and taxonomic importance of this epidermal structure, the functions of nonabsorbent trichomes in remaining Bromeliaceae are not fully understood. The hypothesis that light reflection from these trichome layers provides photoprotection was not supported by spectroradiometry and fluorimetry in the present study; the mean reflectance of visible light from trichome layers did not exceed 6.4% on the adaxial surfaces of species representing a range of ecophysiological types nor was significant photoprotection provided by their presence. Several reports suggesting water repellency in some terrestrial Bromeliaceae were investigated. Scanning electron microscopy (SEM) and a new technique-fluorographic dimensional imaging (FDI)-were used to assess the interaction between aqueous droplets and the leaf surfaces of 86 species from 25 genera. In the majority of cases a dense layer of overlapping, stellate or peltate trichomes held water off the leaf epidermis proper. In the case of hydrophobic tank-forming tillandsioideae, a powdery epicuticular wax layer provided water repellency. The irregular architecture of these indumenta resulted in relatively little contact with water droplets. Most mesic terrestrial Pitcairnioideae examined either possessed glabrous leaf blades or hydrophobic layers of confluent trichomes on the abaxial surface. Thus, the present study indicates that an important ancestral function of the foliar trichome in Bromeliaceae was water repellency. The ecophysiological consequences of hydrophobia are discussed.

Tricomas foliares em tomateiro com teores contrastantes do aleloquímico 2-tridecanona

Duas espécies de tomateiro, Lycopersicon esculentum Mill. (Linhagem TOM 556- padrão com baixo teor da metil cetona 2-tridecanona (2-TD) e Lycopersicon hirsutum Dunal var. glabratum Mill. (Linhagem PI 134417- padrão com elevado teor de 2-TD), foram analisadas em conjunto para identificação e quantificação de tricomas foliares. A parte experimental constou da identificação dos tricomas, baseado na presença ou ausência da cabeça secretora na extremidade apical dos tricomas, arranjo e número de células da cabeça, comprimento dos tricomas, e da quantificação do número de tricomas glandulares e não glandulares nos folíolos. O delineamento utilizado para o número de tricomas foi inteiramente casualizado e as médias comparadas pelo teste de Tukey, a 5%. A identificação e quantificação para as espécies foram: a) TOM 556: Tricomas não glandulares do tipo II + III + V (2590 cm-2 de área foliolar); glandular do tipo VI (16 cm-2); glandular do tipo VII (138 cm-2); b) PI 134417: não glandulares do tipo II + III + V (140 cm-2 de área foliolar); glandular do tipo I + IV (843 cm-2); glandular do tipo VI (83 cm-2); glandular do tipo VII (11 cm-2). As maiores concentrações da 2-TD nos folíolos, estão associadas às maiores densidades de tricomas glandulares presentes em ambas espécies.

The Bornean Lithocarpus Bl. section Synaedrys (Lindl.) Barnett (Fagaceae): its circumscription and description of a new species

The Bornean species of Lithocarpus Bl. section Synaedrys (Lindl.) Barnett (Fagaceae) are discussed in terms of their unifying characteristics, and keys to the species are provided. A novel morphological feature present in the genus, where the seed in the mature fruit is enclosed by a lignified and thickened receptacle, is illustrated. A new species, L. palungensis Cannon & Manos, is described. It can be distinguished from L. pulcher (King) Markgr. by its submontane distribution, prominent reflexed cupular spines, present at all stages, and broadly oblong leaves with scattered open fasciculate trichomes on the abaxial surface. Foliar trichome types present within the section are also described. Distinctiveness of fruit wall and receptacle shape, as described by two-dimensional elliptic Fourier transformation, is demonstrated by principal components analysis.

The Bornean Lithocarpus B1. section Synaedrys (Lindl.) Barnett (Fagaceae): its circumscription and description of a new species

The Bornean species of Lithocarpus B1. section Synaedrys (Lindl.) Barnett (Fagaceae) are discussed in terms of their unifying characteristics, and keys to the species are provided. A novel morphological feature present in the genus, where the seed in the mature fruit is enclosed by a lignified and thickened receptacle, is illustrated. A new species, L palungensis Cannon & Manos, is described. It can be distinguished from L. pulcher (King) Markgr. by its submontane distribution, prominent reflexed cupular spines, present at all stages, and broadly oblong leaves with scattered open fasciculate trichomes on the abaxial surface. Foliar trichome types present within the section are also described. Distinctiveness of fruit wall and receptacle shape, as described by two-dimensional elliptic Fourier transformation, is demonstrated by principal components analysis.

Phylogenetic relationships of Actinidia and related genera based on micromorphological characters of foliar trichomes

The phylogenetic relationships within the genus Actinidia and among 3 allied genera Clematoclethra, Saurauia, and Sladenia have been very controversial. In order to understand the systematic implication of foliar trichomes in those genera, the micromorphological characteristics of foliar trichomes from 34 taxa were examined by means of light microscopy and scanning electron microscopy (SEM). The observed micromorphological characteristics were classified into eight main types. A phylogenetic analysis of Actinidia and related genera based on 15 micromorphological characters of foliar trichomes was conducted using Wagner parsimony method and Sladenia celastrifolia, Rhododendron hybridum and R. simsii as a complex outgroup. In the resulting phylogenetic tree, Actinidia is shown to be a monophyletic group, and Clematoclethra and Saurauia form another monophyletic group. This study also presents the phylogenetic relationships among 4 sections within the genus Actinidia: the monophyly of sect. Leiocarpae and of sect. Strigosae, and polyphyly of sect. Maculatae and of sect. Stellatae.

Macro‐ and micromorphological evidence for infraspecific separation of taxa in Hibiscus rosa‐sinensis L. (Malvaceae)

AbstractThe study was conducted to confirm the traditional separation of varieties of Hibiscus rosa‐sinensis L. according to corolla colour. Measurements were made on live plants of three varieties: red, orange and white, for plant height, number of branches, angles of branches, leaf size and floral whorl dimensions. Leaf shape, apex, base and floral behaviours at anthesis were also assessed. Micromorphological features like stomatal indices, complex types, their distribution on adaxial and abaxial surfaces, presence of foliar trichomes as well as pollen grain features were assessed. Results revealed enough evidence to confirm the traditional separation of these varieties despite the affinity of macromorphometric features. Suggestions were made to attempt explaining the paradox of high pollen grain fertility as against no fruit set and vegetative reproduction in the species.

Physiological and Anatomical Responses to Water Deficits in the Cam Epiphyte Tillandsia ionantha (Bromeliaceae)

Although physiological responses to drought have been examined in several species of epiphytic bromeliads, few have included a comprehensive methodological approach to the study of the carbon and water relations of a single species undergoing drought stress. Thus, physiological and anatomical responses to an imposed drought treatment were examined in the atmospheric Crassulacean acid metabolism (CAM) epiphyte Tillandsia ionantha. From 0 through 20 d without water, nocturnal malic acid accumulation and CO2 uptake rates did not change despite a 17% reduction in relative water content. In addition, water potentials averaged -0.40 MPa and, unlike leaf water content, did not decline. The avoidance of further declines in leaf water content was attributed to the restriction of stomatal opening to the night (a characteristic feature of CAM), to low stomatal densities and small stomatal pores, and to a thick boundary layer resulting from a dense foliar trichome cover. The maintenance of high physiological activity during the first 20 d of the drought treatment was most likely a result of the high water potentials in the chlorenchyma, which were attributed, in part, to water movement from the water-storage parenchyma (= "hydrenchyma") to the chlorenchyma. Nocturnal malic acid accumulation and the rate of net CO2 exchange declined in a linear fashion from 30 to 60 d without water, as did leaf water potential and osmotic potential. During this time, CO2 recycling increased from ca. 20% to nearly 75%. Though declining throughout this later stage of the drought treatment, metabolic activity remained relatively high, possibly as a result of the observed osmotic adjustment as well as a potentially high cell wall elasticity.

Performance of the predator Delphastus pusillus on Bemisia resistant and susceptible tomato lines

AbstractHost plant resistance and biological control are often assumed to act additively to suppress populations of agricultural pests. Using tomato trichome based resistance to the whitefly Bemisia argentifolii, we tested this additivity assumption with Delphastus pusillus, a coccinelid predator of Bemisia. Various life history traits of D. pusillus were measured on the tomato cultivar ‘Alta,’ which possessed foliage with 3‐fold greater trichome densities than the second cultivar ‘VF145B7879.’ Beetles housed on VF145B7879 exhibited significantly greater lifetime fecundities and walking speeds than beetles housed on Alta. No cultivar‐specific differences were observed in D. pusillus longevities or handling times. Combining these observations with previously published reports of reduced B. argentifolii population growth rates on Alta compared to VF145B7879, we tested the hypothesis that increased levels of whitefly biological control could be obtained on VF145B7879 by comparison to Alta through releases of D. pusillus. Analyses of results obtained from replicated population trials detected significant reductions in whitefly populations due to D. pusillus releases, but they did not detect a significant influence of tomato cultivar on the ability of D. pusillus to suppress whitefly populations. Significantly longer beetle residence times on Alta than on VF145B7879 may have compensated for the significantly slower walking speeds and reduced lifetime fecundities observed on Alta and produced a neutral effect of foliar trichome densities on B. argentifolii biological control.

Systematic distribution of foliar trichome types in Croton (Euphorbiaceae)

Abstract Variation in foliar trichomes in Croton (Euphorbiaceae) is reviewed, and the terminology clarified by redefinitions and illustrations of terms. Evolution of trichome types appears to proceed from branched (stellate or fasciculate) hairs to simple and dendritic ones. A systematic enumeration characterizes the trichome morphology in 36 of the 40 sections, with citation of the 120 species examined.

Inheritance of Morphological Characters and RAPD Markers in Intersubgeneric Hybrids of Azalea, (Rhododendron kiusianum Makino*R. indicum (L.) Sweet)*R. japonicum (A. Gray) Suringer f. flavum Nakai.

The inheritance of morphological characters and RAPD (random amplified polymorphic DNA) markers among the intersubgeneric hybrids of (Rhododendron kiusianum Makino × R. indicum (L.) Sweet) ×R. japonicum (A. Gray) Suringer f. flavum Nakai was investigated to clarify the usefulness of RAPD markers in the breeding program of yellowflowered evergreen azalea (Akabane, 1993).Tree forms of the hybrids were similar to R. japonicum f. flavum. Leaf morphology of the hybrids was intermediate to that of the parents. Microscopic observation of foliar trichomes revealed that all the hybrids had long hairs similar to those of R. japonicum f. flavum. The short hair trait of R. japonicum f. flavum. was observed in some hybrids. The degree of defoliation in winter varied among the hybrids.Seven out of 16 primers, generated a total of 28 RAPD bands. The hybrids and their parents could be distinguished by band patterns. Inheritance of RAPD bands was confirmed by Southern hybridization.Variations in morphology and polymorphisms of RAPD pattern among the hybrids were attributed to the heterozygosity and the phylogenetic distance between the parental species. The hybrids that had more paternal RAPD bands tended to exhibit more patrilineal morphological characters. This suggests that some RAPD markers and morphological characters may be linked.

Foliar trichomes of the evergreen and semi-deciduous species of the genus Quercus(Fagaceae) in the Iberian Peninsula

The leaf trichomes of the evergreen and semi-deciduous species of the genus Quercusliving in the Iberian Peninsula were studied by means of SEM and LM. The SEM has been particularly useful because of the high quality of the illustrations and the possibility of recognizing the structures under LM or the stereomicroscope afterwards. The studied species were: Quercus coccifera, Q. ilex, Q. rotundifolia, Q. suber, Q. canariensis, Q. faginea, Q. broteroiand Q. lusitanica.All species show some exclusive particularities that permit their identification using these characters. The abaxial surface of the leaf always has more trichomes than the adaxial and hence provides more characters for identification. Quercus alpestrisBoiss. shows the same features in the leaf trichomes as Q. fagineaLam. A key for identification using these characters is provided.

Foliar trichomes of the evergreen and semi-deciduous species of the genus Quercus (Fagaceae) in the Iberian Peninsula

Abstract The leaf trichomes of the evergreen and semi-deciduous species of the genus Quercus living in the Iberian Peninsula were studied by means of SEM and LM. The SEM has been particularly useful because of the high quality of the illustrations and the possibility of recognizing the structures under LM or the stereomicroscope afterwards. The studied species were: Quercus coccifera, Q. ilex, Q. rotundifolia, Q. suber, Q. canariensis, Q. faginea, Q. broteroi and Q. lusitanica. All species show some exclusive particularities that permit their identification using these characters. The abaxial surface of the leaf always has more trichomes than the adaxial and hence provides more characters for identification. Quercus alpestris Boiss. shows the same features in the leaf trichomes as Q. faginea Lam. A key for identification using these characters is provided.

Phylogenetic Relationships of Didymocistus and Hymenocardia (Euphorbiaceae)

The genus Hymenocardia has been placed either in Euphorbiaceae subfamily Phyllanthoideae or in its own family and then associated with the Urticales, particularly the Ulmaceae. However, the pollen exine wall of Hymenocardia lacks the microchanneled tectum, granular interstitium, and thin foot-layer of the Urticales. Hymenocardia instead has many palynological features found in the Phyllanthoideae and should be retained in the Euphorbiaceae in that subfamily. Didymocistus, which has scalelike foliar trichomes and exine sculpturing and ultrastructure similar to Hymenocardia, should be transferred from the Phyllanthoideae-Aporuseae to a position near Hymenocardia

Effect of acid deposition on trichome morphology and dogwood anthracnose biology

Dogwood anthracnose, caused by Discula destructiva (1), is another new catastrophic tree disease that has ravaged natural populations of the flowering dogwood (Cornus florida) in the Appalachians over the past 15 years, and the epidemic is prognosticated to continue (2). An estimated 9.5 million acres have been affected, primarily in the Appalachian Mountains, from VA southwards, alone, and an estimated 50% of all dogwoods in PA have been killed. Since acid deposition has been linked experimentally with disease induction, and since the disease incidence and severity are more pronounced at higher elevations where lower pH precipitation events occur, we investigated the effect of acidic foliar sprays on moiphologic changes in the foliar cuticle and trichomes (3), the initial sites of infection and foci of Discula sporulation.