Multiple Epidermis Research Articles

Hypodermis or multiple epidermis: Leaf ontogenesis in nine species of subfamily Myrtoideae (Myrtaceae)

The ninth largest family of angiosperms is Myrtaceae, which comprises 127 genera and over 6000 species. The leaf anatomy of Myrtaceae has been widely studied and can be used in phylogenetic analyses and species delimitations in complexes within the family. A multiple epidermis and hypodermis have been described for the leaves of representatives of the family but have not been confirmed using ontogenetic studies, which could lead to incorrect interpretations about these tissues. Thus, we studied the leaf ontogenesis of the following 9 species in subfamily Myrtoideae: tribe Syzigieae - Syzigium cumini; tribe Myrteae - Myrceugenia alpigena and M. euosma (subtribe Luminae), Psidium sartorianum, P. guajava, Campomanesia adamantium and Pimenta pseudocaryophyllus (subtribe Pimentinae), Myrcianthes pungens and M. gigantea (subtribe Eugeniinae). Shoot apices and leaves up to the fourth node were transversally and longitudinally sectioned following techniques used for plant anatomy. Leaf development in all species is from apical, intercalary, dorsal, marginal and plate meristematic activity. Protodermal periclinal divisions only occur to give rise to secretory cavities. The results show that in all the species the subepidermal layer is a hypodermis, which originates from periclinal divisions of the ground meristem. The occurrence of this layer could have phylogenetic implications according to reports in the literature, reinforcing the relationships among the subtribes in current topologies of Myrteae. However, the occurrence of a hypodermis in representatives of other subtribes of Myrteae and Syzigieae need to be better studied and discussed in relation to the phylogeny of Myrtaceae.

A multiple epidermis or a periderm in Parkinsoniapraecox (Fabaceae)

A multiple epidermis in the green stems of Parkinsonia species has been described; however, there are disagreements among authors with regard to origin and tissues involved. The aims of this study were to identify the origin and development of the epidermis and cortex of P. praecox and relate these to possible adaptations to arid environments. Samples from new branches, to the stem, were removed and prepared using two embedding techniques. Our results show that the epidermis is simple, but periclinal divisions start far from the apical meristem. The inner derivatives maintained periclinal and anticlinal divisions, which are interpreted as meristematic, promoting continuous cell renewal. Wax and cutin deposits suggest that a special epidermis is present; however, it does not correspond to a multiple one. The cortex has four distinct regions. As the branch circumference increases, modifications occur in the first, second, and fourth regions, and sclerenchyma with abundant prismatic crystals develops. The third region maintains its identity with abundant chloroplasts. The occurrence of crystals and chlorenchyma improves structural stiffness, increases the reflectivity of plant surfaces, and facilitates the recycling of respiratory CO2. Abundant waxes, chlorenchyma, sclerenchyma, and crystals in the stems may be adaptations of P. praecox to xeric environments.

Origin, activity and environmental acclimation of stem secondary tissues of the polar willow (Salix polaris) in high-Arctic Spitsbergen

High Arctic is an intensively explored region in relation to predicted global warming. Its long-term impact is analysed in dwarf-shrubs, such as a widely distributed and pioneering species Salix polaris (polar willow). Understanding the functioning of lateral meristems in these dwarf-shrubs is however limited, affecting interpretation of the data. The presented study focused on the formation and anatomy of the derived secondary tissues in the stems of S. polaris from polar habitats. The entire branches of the polar willow were collected in five vegetation types of tundra located in SW Spitsbergen (Svalbard) and analysed on the series of transverse and longitudinal sections. Our analyses showed that the periderm developed in two or three-year old stems as the secondary protective tissue, and that the multiple epidermis, typical of many willow species, was not formed in S. polaris. The secondary xylem in the polar willow stems showed considerable differences in diameter and length of vessel elements within a single stem. Importantly, the size of the vessel elements differed also depending on the tundra vegetation type. Our findings suggest that the soil moisture was a main factor determining the size of vessels, and that their size was not correlated to the nitrogen supply. Our study thus demonstrated the usefulness of different anatomical features of wood, in above-ground organs, in High Arctic research.

Ficus pongumphaii (Moraceae), a new species from Thailand, compared with the ambiguous species F. talbotii

A deciduous shrub previously included in Ficus talbotii for many years, is now regarded as a new species, Ficus pongumphaii. It is morphologically distinct from F. talbotii with as typical characters the densely brown pubescent to tomentose or villous on leafy twig; the elliptic, suborbicular to obovate leaf blades that are brown tomentellous on the upper surface and brown floccose tomentose to villous underneath; the pedunculate figs are obovate, brown floccose or villous outside and have internal hairs. The leaf anatomy shows a multiple epidermis on both surfaces; enlarged lithocysts on both sides of the lamina, which are more abundant adaxially and with very few abaxially. The species, endemic to Thailand, is named after the great Thai dendrologist, Associate Professor Somnuek Pongumphai.

The velamen of epiphytic orchids: Variation in structure and correlations with nutrient absorption

Roots of epiphytic orchids typically possess a velamen radicum, a multiple epidermis composed of dead cells. It is largely unexplored how the structure of the velamen, the cortex and vascular cylinder facilitate the flow of water and nutrients towards the plant. Up to now, structural root features were rarely correlated with functional attributes. In this study, we compare anatomical features with nutrient uptake rates (specifically of phosphorus and rubidium) of roots of 18 taxa of epiphytic orchids. The relative proportion of the velamen of the cross-sectional area varied from 11 to 97%. Species with the largest relative velamen area facilitate the flow of water and nutrients, and species with larger relative proportion of vascular cylinder and cortex have a greater number of protoxylem strands and passage cells of the endodermis. The number of passage cells in the endodermis and of differential wall thickenings in cortical cells may play an important role in apoplastic and symplastic flow. The velamen pectic matrix, with negative charge, can retain cations (like Rb+), while a higher number of strands in the xylem, aligned with passage cells of the endodermis, could facilitate the entry of these ions into the vascular cylinder.

Sucking herbivore assemblage composition on greenhouse Ficus correlates with host plant leaf architecture

Understanding arthropod herbivore selectivity trends towards host plant attributes is essential for predicting plant-associated herbivore assemblage structure. Little is known about such interactions between spontaneous herbivore species and cultivated plants under specific conditions of botanical garden greenhouses. In this study, the taxonomic and functional composition of sucking arthropod herbivore assemblages were correlated with leaf anatomical and surface features of 33 host species of Ficus L. (Moraceae) across four distantly located greenhouse complexes of botanical gardens. The analyses revealed that the species number and abundance of scale insects and their individual families, sessile phloem feeders, total phloem feeders and total herbivores were significantly positively correlated with the thickness of leaf lamina, epidermis and mesophyll, stomatal length and width, and the presence of abaxial multiple epidermis and weak ferruginous non-glandular trichomes. Significant negative correlations were revealed between the same herbivore parameters and the density of glandular trichomes. Heliomorphic leaves supported higher abundance and species richness of sessile phloem feeders compared to sciomorphic ones. The parameters of some phloem and mesophyll feeder taxa also correlated with non-glandular trichome length and density, type of trichomes and epicuticular wax layer, and the presence of calcium oxalate crystals in the epidermis. Results of the study suggest that the leaf architecture-related herbivory trends under greenhouse conditions are similar to those occurring in natural ecosystems when considering the functional significance of particular leaf traits, and remain relevant at the scale of particular plant taxa with disregard of spatial factor.

Origin of the subepidermal tissue in Piper L. leaves.

Studies on the anatomy of Piper leaves demonstrate the presence of a subepidermal tissue distinct from the adjacent epidermis, which cells show thin walls and hyaline contents. Some authors consider such cells a hypodermal tissue, while others refer to them as components of a multiple epidermis. In this study, the nature of this subepidermal tissue was investigated through the analysis of leaf ontogeny in three Piper species. The analysis showed that the referred tissue originates from the ground meristem and, thus, should be considered a hypodermis. The studied species suggests that the role of the hypodermis would be to protect the photosynthetic apparatus from excess light, regulating the intensity of light reaching the chlorophyll parenchyma.

Comparative pharmacognostical evaluation of nine different varieties of the leaves of Psidium guajava Linn.

Objective: To explore the micro morphology and Physio chemical parameters of nine different varieties of the leaves of Psidium guajava Linn. (Myrtaceae). Methods: Macroscopy, microscopy, physicochemical analysis, preliminary phytochemical screening and other WHO recommended parameters for standardizations were performed. Results: Leaves (5-15cm × 4-6 cm) are dorsiventral, oblong – elliptic, dull grey to yellow green with entire margin, obtuse to bluntly acuminate apex and rounded to subcuneate base with short petiole. Morphology of the leaves showed no difference in all the varieties. A noteworthy feature Myrtaceae family is the presence of secretory cavities. Microscopic evaluation revealed that secretory cavities were absent in Bangalore, Chittidhar and it is present in the lower side in case of Anakapalli, Hafsi, Lucknow-46, Nagpur seedless and Red fleshed, but it was 80µm wide and present in the upper portion in Smooth green. Narrow secretory cavities observed at the periphery of the midrib in Lucknow-49. Calcium oxalate druses in dilated cells are present in Hafsi and Lucknow-46 alone. All varieties contain invariably multiple epidermis. Tannin is abundant in the tissue, but it is very less in Lucknow-49 and dark tannin accumulation seen in Red fleshed. In vascular bundle xylem less lignified, uniseriate thick walled in Anakapalli, thin walled dark elliptical sclerenchyma in Bangalore variety. Powder microscopy showed the presence of paracytic stomata, fragment of epidermis, conical and flagellate trichomes, fragment of palisade mesophyll, secretory cavity (absent in Bangalore, Chittidhar varieties), calcium oxalate crystals (present in Hafsi and Lucknow -46 varieties) and parenchymal cells. Vein islet & Termination number, stomatal number & index and other physico chemical tests like ash values, loss on drying, extractive values were determined. Preliminary phytochemical screening showed the presence of sterols, tannins, proteins and amino acids, flavonoids, volatile oil, terpenoids, saponin, carbohydrates and absence of alkaloids, mucilage, glycosides, fixed oil. Conclusion: Microscopic analysis was informative and provides useful information in the botanical identification, standardization for purity & quality and immense value in authentication of the different varieties of the leaves.

Leaf anatomy ofFicussubsectionUrostigma(Moraceae)

Species of Ficus subsection Urostigma show much overlapping variation in vegetative morphology, which often precludes correct identification of the species. The aim of this study was to describe the leaf anatomical characters and their variation and to check their suitability for identification. Included were 41 samples belonging to 25 species of subsection Urostigma, four samples belonging to two species of section Leucogyne and one specimen of Ficus glaberrima subsp. siamensis of subsection Conosycea. Transverse sections of lamina, midrib and petiole and cuticular macerations were used, and the observed anatomical characters are described for each species. On the basis of a limited number of studied samples, leaf anatomy shows little variation within each species and each species has a unique combination of character states, facilitating identification. Ficus arnottiana shows some leaf anatomical characters that are quite different from those of other members of subsection Urostigma, including a multiple epidermis and enlarged lithocysts on both sides of the leaf. Both characters are generally considered as typical for Ficus subsection Conosycea. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 259–281.

<I>Ficus cornelisiana</I>, a new species of <I>Ficus</I> subsection <I>Urostigma</I> (Moraceae) from the Sino-himalayan region

A small fig tree has been misidentified as Ficus orthoneura for a long time. However, morphologically it is distinct from F. orthoneura and F. hookeriana. Typical are the ellipsoid, puberulous receptacle and caducous basal bracts. Leaf anatomy shows a multiple epidermis with the cells in the inner layer much larger than in the outer layer and thus both layers resemble an epidermis with a separate hypodermis. The abaxial cuticle is strongly sculptured, the palisade layer shows some long subdivided cells, and enlarged lithocysts are only present abaxially. Because of these differences we hereby describe it as a new species, named in honour of Cornelis (Cees) Berg: Ficus cornelisiana.

Aerial roots of epiphytic orchids: the velamen radicum and its role in water and nutrient uptake

The velamen radicum, a spongy, usually multiple epidermis of the roots, which at maturity consists of dead cells, is frequently described as an important adaptation of epiphytic orchids. Yet, quantitative evidence for the alleged functions, e.g., efficient water and nutrient uptake, nutrient retention, reduction of water loss, mechanical protection, or the avoidance of overheating, is rare or missing. We tested the notion originally put forward by Went in 1940 that the velamen allows plants to capture and immobilize the first solutions arriving in a rainfall, which are the most heavily charged with nutrients. In a series of experiments, we examined whether all necessary functional characteristics are given for this scenario to be realistic under ecological conditions. First, we show that the velamen of a large number of orchid species takes up solutions within seconds, while evaporation from the velamen takes several hours. Charged ions are retained in the velamen probably due to positive and negative charges in the cell walls, while uncharged compounds are lost to the external medium. Finally, we demonstrate that nutrient uptake follows biphasic kinetics with a highly efficient, active transport system at low external concentrations. Thus, our results lend strong support to Went's hypothesis: the velamen fulfills an important function in nutrient uptake in the epiphytic habitat. Most of the other functions outlined above still await similar experimental scrutiny.

Structural and functional leaf traits of two Gochnatia species from distinct growth forms in a sclerophyll forest site in Southeastern Brazil

Gochnatia is very common in different phytophysiognomies in the Cerrado of São Paulo State, occupying open and closed areas. In this study, we compared the leaf anatomy and some ecophysiological traits of two species of Gochnatia, one a shrub (Gochnatia barrosii Cabrera) and the other a tree (Gochnatia polymorpha (Less.) Cabrera), which both occur in an area of "cerradão" at the Estação Ecológica de Assis, SP. We found qualitative structural differences between the species, with G. barrosii presenting amphistomatic leaves with a uniseriate epidermis and G. polymorpha showing hypostomatic leaves and a multiple epidermis or hypodermis on the adaxial surface. Moreover, the G. barrosii leaves had lower values in tissue thickness (with the exception of the epidermis on the abaxial surface) and leaf thickness in relation to G. polymorpha. There were differences in CO2 assimilation both in area and leaf dry mass basis, and differences in specific leaf area, which was higher in G. barrosii. Although the G. barrosii leaves were much less sclerophyllous than the G. polymorpha leaves, we found no differences in the efficiency of water use. The results suggest that plants from the same genus, but with distinct growth forms, differ in their leaf traits to deal with the environmental variations that they grow in.

Red young leaves have less mechanical defence than green young leaves

In many plants, leaves that are young and/or old (senescent) are not green. One adaptive hypothesis proposed that leaf color change could be a warning signal reducing insect attack. If leaf coloration involves less herbivory, it remains unclear why leaves in many species are constantly green. To examine whether green leaves reduce herbivory by physical defense as an alternative to the supposed warning signal of red leaves, we conducted comparative analyses of leaf color and protective tissues of 76 woody species in spring. The protective features (trichomes, enhanced cuticle and multiple epidermis) and the distribution of red pigments within leaves were examined in both young and mature leaves. We observed that redness was more frequent in young leaves than in senescent leaves. Compared to 36 species with red young leaves, 40 species with green young leaves showed a significantly higher incidence of enhanced cuticle and trichomes in both phylogenetic and non‐phylogenetic analyses. The phylogenetic analysis indicated that the multiple origins of mechanical protection were generally associated with loss of red coloration. Our finding of relatively poor mechanical protection in red young leaves provides additional evidence for the adaptive explanation of leaf color change.

Do leaves in Cyperoideae (Cyperaceae) have a multiple epidermis or a hypodermis?

In Cyperaceae, leaf anatomical characters, in particular the presence of a hypodermis or of a multiple epidermis, have contributed in taxonomic and phylogenetic studies. In this family, the leaf epidermis is often described as uniseriate, and the cells of the subepidermal layers having no chloroplasts are treated as hypodermis. Both tissues have a different ontogenetic origin and hence are not homologous. The aim of the present work was to verify the origin of the subepidermal layers in eight species belonging to Cyperoideae. All species studied presented multiple epidermal layers that were confirmed by leaf ontogeny. In Fimbristylis complanata, F. dichotoma, Pycreus flavescens and P. polystachyos the mature leaves present multiple epidermal layers with cells of the distinct layers similar in shape and size; in the other species studied these cells are different. Especially in the latter case, a multiple epidermis is easily interpreted erroneously as a hypodermis, possibly leading to erroneous evolutionary conclusions. Making correctly distinction between a hypodermis and a multiple epidermis, and hence in case of doubt investigating the origin of the questioned tissue, is compulsory in order to use both characters in a phylogenetic context. Though in the past often called ‘hypodermis’, our leaf ontogenetical observations show that in all species studied, the subepidermical layers constitute a multiple epidermis, originating from the protodermis.

Cambios anatómicos en la corteza de <em>Parkinsonia praecox</em> (Ruiz et Pavón) Hawkins causados por la epífita <em>Tillandsia recurvata</em> L. (Bromeriaceae)

Tillandsia recurvata L. is commonly found growing on the branches and trunk of Parkinsonia praecox (Ruiz et Pavón) Hawkins in the semi-arid area of the Zapotitlán Salinas Valley, Mexico, and this relationship seems to affect the phorophyte in different ways. The purpose of this study was to evaluate the effect of the establishment of T. recurvata on bark tissues of the phorophyte P. praecox. The anatomical study of the bark allowed to recognize the presence of non-collapsed phloem, collapsed phloem, a cortex whose cells under the epidermis show chloroplasts and a multiple epidermis covered by a wide epicuticular wax layer. Tillandsia recurvata roots never penetrate the tissues. However, in those zones where the epiphyte occurs a wound periderm develops below the epidermis. Wound periderm provides protection against infection, but it probably also affects negatively the mobilization of carbon dioxide toward internal tissues or the dissipation of heat and light. These aspects seem to be more important than the photosynthesis decrease in branches where the epiphyte establishes. It is likely that the overweight caused by the large number of Tillandsia recurvata individuals on the branches prevents the adequate architectural development of the phorophyte Parkinsonia praecox.

ANATOMICAL FEATURES, OTHER THAN WOOD, IN SUBFAMILY OPUNTIOIDEAE (CACTACEAE)

Abstract Fifty species of Opuntioideae were examined to establish 1) the range of anatomical variation occurring in this subfamily, 2) characters these plants share with other desert-adapted plants, and 3) information about phylogenetic relationships within Cactaceae. Only three characters are universally present in stem-photosynthetic, stem-succulent plants: 1) a persistent epidermis, 2) a thickened cortex, and 3) a palisade cortex. A multiseriate hypodermis with extremely thick walls and crystals is almost universally present in Opuntioideae and Cactoideae but is not uniformly present in non-cactus succulents. Opuntioideae lack many features common in Cactoideae: they have no extremely thick cortex, no extensive system of cortical bundles, no collapsible cortex cells, and no medullary bundles. Features common to Pereskia, Cactoideae and Opuntioideae, which may be relictual in the family, are 1) a tendency to form multiple epidermis, 2) a multiseriate, thick-walled hypodermis with druses in at least one ...

The Structure of Photosynthetic Succulent Stems in Plants Other Than Cacti

In an investigation of succulence as an adaptation to water‐stressed desert environments, we studied the anatomy of photosynthetic succulent stems in 28 species from Apocynaceae, Asclepiadaceae, Asteraceae, Crassulaceae, Didieriaceae, Euphorbiaceae, Geraniaceae, and Vitaceae. Only species with enlarged pith or cortex were examined, not species with enlarged parenchymatous wood. The numbers of species with particular characters are as follows: pith is the most voluminous tissue—5 species; cortex is the most voluminous tissue—22; cortical bundles present—0; medullary bundles present—4; palisade cortex present—16; epidermis with thick or lignified walls—0; epidermis outer wall somewhat thickened—6; multiple epidermis present—0; cuticle >2 μm thick—4; cuticle <1 μm thick—3; hypodermis cells with very thick walls—0. These species lack many features typically considered xeromorphic and associated with desert‐adapted plants; they also lack many features present in most cacti. Absence of cortical bundles in all these noncactus succulents may be especially important: none has a particularly thick cortex (most are <5 mm thick), all are relatively small plants, and absence of cortex vascularization may prevent them from evolving to be truly voluminous. Also, none has truly large shoot apical meristems such as occur in cacti with broad shoots.

Comparative leaf anatomical studies of some Sterculia L. species (Sterculiaceae)

Abstract A comparative study was undertaken on the leaves of 12 Sterculia species in order to assess anatomical variations which may be useful in species identification and to evaluate their significance in the taxonomy of the genus. All species have glandular and non-glandular trichomes, anomocytic stomata, multiple and mucilaginous epidermis, mucilaginous cavities and druses in mesophyll tissues. A small amount of variation was observed in the outline of transverse sections of midribs and petioles, the presence of central vascular bundles, and the type of trichomes. Some characters, such as the vertically divided adaxial epidermis in S. macrophylla , are unique to certain species and are therefore useful in diagnostic characters, while S. coccinea and S. elongata appear to be similar in the structure of the petiole and midrib. The results, however, do not show any groupings of species and do not support the observations of others on groups derived from wood anatomy.

Natural Abundance 2H/ 1H Ratios of Water Storage in Leaves of Peperomia Congesta HBK during Water Stress

Summary The mixing patterns of water from the water-storage multiple-epidermis (ME) and the spongy parenchyma (SP) of leaves of Peperomia congesta HBK were studied by following variations in the natural abundance of deuterium. The 2H/1H ratios of water from the two tissues were different throughout the diel cycle and were always lower in the ME. Withholding water from the potted plants resulted in complete isotopic homogeneity of leaf water within 3 days. Isotopic homogeneity and the extent of 2H enrichment of leaf water were constant for the duration of the 3-week stress period while the weight of the ME differentially and continuously decreased during the same period. Reinstating irrigation resulted in the rapid restoration of pre-stress ME weight, and a simultaneous sharp drop in the 2H/1H ratio of water in both the ME and SP. The proportion of recharge by soil water was similar whether calculated based on changes in tissue weight or on 2H/1H ratios. In contrast to the rapid recovery in water content, isotopic enrichment and restoration of isotopic heterogeneity were gradual over several days. The results indicate that under favorable conditions water, and not only solutes, stored in the ME does not mix well with water in other tissues, but becomes a more integral part of total leaf water under water stress conditions. In recovery from water stress, recharge with soil water is rapid (hours) while communication with the external environment, as reflected by isotopic enrichment and restoration of isotopic heterogeneity in leaf water, is gradual (days). The results demonstrate the potential of using stable isotopes at the natural abundance level to study the dynamics of water movement within plants.

Differential expression of photosynthesis genes in leaf tissue layers of Peperomia as revealed by tissue printing

Peperomia has species that may be C3, show Crassulacean acid metabolism (CAM), or CAM‐cycling. Species that show CAM progress from C3 to CAM through CAM‐cycling during leaf development. In CAM and CAM‐cycling species, CAM metabolism is predominately in the upper multiple epidermis and lower spongy mesophyll, whereas C3 metabolism is localized mostly in the palisade mesophyll. Using specific protein and cDNA probes prepared from P‐enolpyruvate carboxylase (PEPc) and ribulose‐1,5‐bisphosphate carboxylase (Rubisco), we have now studied the differential distribution of photosynthetic metabolism in Peperomia leaves using the technique of tissue printing. The tissue printing studies detected Rubisco protein in leaves of C3 P. orba, but not PEPc. Young C3 leaves of P. scandens and P. camptotricha showed Rubisco protein, but not PEPc; however, the mature leaves of these two species that have CAM showed PEPc protein and RNAs in both the multiple epidermis and spongy mesophyll. In contrast, Rubisco protein and RNAs were present throughout the leaf. The tissue printing data are consistent with our previously published data showing the differential distribution of photosynthetic metabolism in leaves of Peperomia. Although the tissue printing technique is qualitative, coupled with quantitative data it has proven useful for the study of function related to structure.