Leaf Architectural Characters Research Articles

Applications of leaf architecture characters in delineating selected species and infraspecific taxa of Genus Cucumis L. (Cucurbitaceae)

Leaf venation characters of twelve (12) Cucumis taxa, comprised of eight species, three subspecies, and three varieties were examined to determine patterns of leaf architectural characters and delineate these accessions at the species, subspecies, and variety level. The leaf architecture of twenty-seven accessions representing six taxa were examined and described in this study. Additionally, data on the leaf architecture of another six taxa (represented by 57 accessions) published by Masungsong et al. (2022) were incorporated in the analysis. Results revealed that the twelve (12) taxa of Cucumis primarily varied in blade class, apex angle, primary vein size, secondary vein spacing, tertiary vein angle to primary vein, and areole development. These variations were found consistent with Cucumis species examined in previous studies. A dichotomous key was constructed for the twelve Cucumis taxa using leaf characters derived. Cluster analysis (based on UPGMA) formed two major clusters at 0.130 Gower distance. Cluster I includes Cucumis melo subsp. melo, C. pustulatus, C. melo var. flexuosus, C. melo subsp. agrestis, and C, melo var. texanus which exhibited secondary vein spacing that increases towards the base. while Cluster II is composed of the remaining Cucumis taxa, all displaying irregular secondary vein spacing. Furthermore, sub-clusters were formed based on tertiary vein angle in relation to primary vein, blade class, apex angle, and primary vein size. Results showed that utilizing leaf architecture is an effective technique to describe, characterize and delineate closely related taxa with many similar characters.

Morphological , Anatomical and Chemical Studies of Salvia Rosmarinus Spenn. Growing in Al- Marj (Libya)

Salvia rosmarinus Spenn (synonym: Rosmarinus officinalis L.) is economically and medically important and grows naturally in Al-Marj (Libya). Macro, micro morphological and chemical characteristics were studied. Leaf venation, leaf anatomy and chemical compounds of essential oils were carried out according to traditional methods. The objective of the present study is to provide detailed description of the characteristics of this species. Morphological charactersistics of leaves, calyx, corolla, stamens are useful for sectional and specific delimitations in Salvia. The leaf architecture characters of primary, secondary, tertiary and quaternary veins are good diagnostic markers for the identification and classification of species. Anatomical characters such as glandular and non- glandular trichomes , mesophyll structure, presence of hypodermis and structure of vascular bundles have been found to have taxonomic value. Cineol (32.38%) is main component of essential oil, followed by Camphor, β-pinene, borneol, Caryophyllene, α-terpineol and α-pinene. Chemical data in essential oils carried taxonomic value of Salvia species.

Macromorphological, Anatomical And Molecular Studies Of Some Taxa Of Araliaceae In Egypt

The present study investigated morphological features, leaf and stem anatomy, leaf architecture, epidermal characteristics, and molecular characters of some taxa of Araliaceae to trace out the diversity and the diagnostic significance of these attributes. The studied taxa based on combination of 260 characters representing 182 morphological and 78 molecular characters which were subjected to a numerical analysis using NTSYSPC program. The generated dendrogram explained the similarities and the differences between the examined taxa. The specific similarities are discussed and compared with some current classification systems. The generated dendrogram from morphological attributes confirmed the separation of Aralieae and Schefflerieae as two tribes of Araliaceae and supported the separation of simple leaved taxa from compound leaved. Bangladesh J. Plant Taxon. 29(2): 283-296, 2022 (December)

Rapid character scoring and tabulation of large leaf-image libraries using Adobe Bridge.

Digital image libraries are an integral part of specimen-based research. However, coding and extracting metadata for hundreds of specimens on a personal computer can be complex. In addition, most existing workflows require downsampling or platform switching and do not link character data directly to the images. We demonstrate a method to code and embed into images the standard leaf architecture and insect-damage characters that are widely used in paleobotany. Using the visual file browser Adobe Bridge, customizable and searchable keywords can be applied directly and reversibly to individual full-resolution images, and the data can be extracted and formatted into a matrix using scripts. Our approach is intuitive and acts as a digital mimic and complement to the experience of sorting and analyzing specimens in-person. Keywords can be easily customized for other data types that require visual sorting using image libraries.

Classifying fifty-seven Cucumis (Cucurbitaceae) accessions into six species using leaf architectural traits

Abstract. Masungsong LA, Alcala AA, Buot IE Jr., Belarmino MM. 2022. Classifying fifty-seven Cucumis (Cucurbitaceae) accessions into six species using leaf architectural traits. Biodiversitas 23: 4006-4017. In gene banks, there are myriads of accessions that need to be studied, grouped, classified and organized to the proper taxon and hence, be able to manage the accessions efficiently. Using leaf architecture traits, it is the objective of this study to determine the identity and classify the 57 Cucumis accessions in the genebank of Hortanova Farm and Research Center, East-West Seed Company, Inc., Lipa City, Batangas, Philippines. Five hundred thirteen Cucumis leaf samples across the 57 accessions were collected, measured, thoroughly investigated, and described using leaf architectural characters. Results of leaf architectural analyses focusing on the blade class, apex angle, secondary vein spacing, tertiary vein angle in relation to primary vein, and areole development, revealed that the 57 accessions can be grouped into six (6) species of Cucumis, namely, C. melo subsp. agrestis (Naudin) Pangalo, C. melo var. texanus Naudin, C. melo var. flexuosus (L.) Naudin, C. zambianus Widrl, J.H.Kirkbr., Ghebret. & K.R.Reitsma, C. sativus L., and C. sativus var. hardwickii (Royle) Gabaev. Cucumis sativus and C. sativus var hardwickii were delineated from the rest of the species for having a macrophyll blade class, an odd lobed acute apex angle and an obtuse tertiary vein angle in relation to the primary vein. This delineation is illustrated in the constructed dichotomous botanical key. Utilizing leaf architecture characters is an effective technique to characterize, identify and classify closely related taxa possessing confusing characters.

Comparative analysis of the leaf architectural characters of Saurauia bontocensis Merr. and Saurauia polysperma (Blanco) Merr. with the application of Digital Image Analysis Software

Abstract. Daipan BPO, Buot IE Jr., Daipan HMO. 2022. Comparative analysis of the leaf architectural characters of Saurauia bontocensis Merr. and Saurauia polysperma (Blanco) Merr. with the application of Digital Image Analysis Software. Biodiversitas 23: 3869-3875. Major confusion still exists among several authors concerning the taxonomy of the dagwey plant. This species is economically significant to the Ikalahan tribe of Luzon, Philippines. Several papers claimed that the plant is Saurauia bontocensis, while others stated that it is Saurauia subglabra. Many botanical websites claimed that S. subglabra is synonymous with S. polysperma, while another article distinguished S. subglabra from S. polysperma. Thus, to help resolve the taxonomic ambiguities, this paper performed a comparative analysis of the leaf architectural characters of S. bontocensis and S. polysperma with the aid of digital image analysis software and cluster analysis. Results revealed that the blade characters alone, delineate the two species, particularly, in terms of the laminar size, shape, symmetry, leaf L:W ratio, base and apex angle, and base shape. Additionally, the leaf venation characters delineate the two species, specifically, on the 2º to 5º vein categories, 2º vein angle, 3º vein course, 3º vein angle to 1º, areolation, freely ending ultimate veins, marginal ultimate venation, and leaf rank. Generally, S. bontocensis have larger, longer, and wider leaves compared with the S. polysperma. The leaf architecture analysis performed in this paper produced a very promising result in differentiating the two Saurauia species and could be used to address some of the taxonomic confusion of these species. The study indicated that S. bontocensis and S. polysperma are two distinct species. Moreover, the use of digital image analysis software was very helpful in the computations of the various blade characters, particularly the digital herbarium exsiccate in the absence of actual leaf samples.

Numerical Taxonomic Evaluation of Leaf Architectural Morphology of Vitex L. species (Lamiaceae Martinov) in Peninsular Malaysia

A numerical taxonomic is an algorithm method that is used to evaluate scored characters of continuous characters such as leaf architectures. Leaf architecture characters were scored from 11 Vitex species in Peninsular Malaysia (V. gamosepala, V. glabrata, V. longisepala, V. millsii, V. negundo, V. pinnata, V. quinata, V. trifolia, V. vestita, Vitex sp.1 and Vitex sp.2), one subspecies (V. trifolia subsp. litoralis) and two varieties (V. negundo var. bicolor and V. negundo var. cannabifolia) were investigated using herbarium voucher specimens and fresh specimens collected from the fieldwork. Species collected were from Pasoh Forest Reserve, Negeri Sembilan; Gunung Lambak Forest Reserve, Johor; Sungai Dara Forest Reserve, Perak; Proton City, Tanjong Malim, Perak; Gunung Lambak Forest Reserve, Johor; Cameron Highland, Pahang; Herb Walk Garden, Langkawi; and Kg. Pulau Belanga, Kota Bharu, Kelantan. All the studied Vitex species shared leaf architecture as follow: arrangement (opposite), marginal ultimate (looped), position of petiole arrangement- P.O.P.A (marginal) and petiole feature (swollen base). Specimens with single leaf type and presence of petiolule further help in distinguishing Vitex species. The scored data were analysed using Multi-Variate Statistical Package (MVSP) and Phylogenetic Analysis Using Parsimony (PAUP) softwares to obtain similarity values between species and their evolutionary relationship, respectively. Dendogram clades show an overall Gower General Similarity Coefficient (GGSc) value at 0.715 to 0.964 which indicate clear separation at genus and species level while pairwise distance between the in-group and out-group taxa analysed in the neighbour-joining tree was in between 0.26364 to 0.55455 showing that trees were constructed with strong bootstrap support with Consistency Index (CI) 0.6852 (CI) excluding uninformative character = 0.6000, Homoplasy index (HI) 0.3148 (HI excluding uninformative character = 0.4000), Retention Index (RI) 0.5802 and rescaled consistency index (RC) 0.3976. As a conclusion, high similarity in leaf architecture characters of all 11 species, one subspecies and two varieties of Vitex studied in Peninsular Malaysia suggest and support them belongs to the same genus hence supporting the taxonomic significance. This study implicate that leaf architecture morphological characters of vegetative parts can be used in identification to species, subspecies and variety level of this genus and might propose some changes to the placement of taxa hence can be devoted as an improvement for the previous Vitex study.

An Extinct Transitional Leaf Genus of Nymphaeaceae from the Eocene Lake at Messel, Germany: Nuphaea engelhardtii Gee et David W. Taylor gen. et sp. nov.

Premise of research. Although the Nymphaeaceae are an ancient angiosperm family, fossil leaves with nymphaeacean affinities from the Paleogene have nearly always been assigned to modern genera. Yet during the diversification of this group, it is extremely likely that transitional forms in this family evolved since its origin over 100 million years ago and should show up in the fossil record. Here, we describe an extinct genus of nymphaeacean leaf with transitional characters from the Eocene Lake Messel locality, which is, according to phylogenetic analysis, a member of the main Nymphaeaceae clade excluding Nuphar. Methodology. Over 39 fossil leaves from the Messel Pit near Darmstadt, Germany, were studied, coded for 40 of 55 morphological and leaf architecture characters, and analyzed phylogenetically. Analyses were run with PAUP* of the Messel leaf morphotype combined with living taxa and then together with previously described fossil Nymphaeales. Pivotal results. Inclusion of the Messel leaf with living taxa results in three trees with similar topology except for the relationship within Nuphar. Bootstrap data strongly support inclusion of the Messel leaf in the order Nymphaeales and the family Nymphaeaceae. In analyses with only living taxa, the Messel leaf places beyond Nuphar within the remaining Nymphaeaceae. In analyses with living and other fossil taxa, it places at the base of the Nuphar clade. Based on its suite of characters, the Messel leaf is recognized here as an intermediate between existing genera and described as a new extinct genus and species. Conclusions. The Eocene water lily from Messel is described here as a new genus and species, Nuphaea engelhardtii Gee and David W. Taylor gen. et sp. nov., and is represented by leaves with characters that are transitional to those of modern Nuphar, Nymphaea, and other Nymphaeaceae. This study offers new evidence of greater biodiversity in Nymphaeaceae in the Cenozoic.

Short Communication: Leaf architectural analysis of taxonomically confusing coffee species: Coffea liberica and Coffea liberica var. dewevrei

Abstract. Baltazar AMP, Buot JrIE. 2019. Short Communication: Leaf architectural analysis of taxonomically confusing coffee species: Coffea liberica and Coffea liberica var. dewevrei. Biodiversitas 20: 1560-1567. Coffee is considered as one of the most important crops. The Philippines is known to produce four coffee varieties namely: Arabica (Coffea arabica), Robusta (Coffea canephora), Excelsa (Coffea liberica var. dewevrei) and Liberica (Coffea liberica). Further, the taxonomy of C. liberica and C. liberica var. dewevrei is still unclear. Since its earliest publication, the relationship of the two taxa have been confusing many taxonomists and also farmers. The status of the two confusing taxa are still under discussions due to contradicting evidence inferred from morphological and molecular data. The two taxa have been claimed as separated species but the markers are considered inconsistent in the field. This study has tried to examine the leaf architectural characters of both species as these have been known to be genetically fixed. Leaf samples of each species including C. canephora (outgroup) were collected and examined. Results showed that the two taxa were found to be different in laminar size, domatia distribution, major secondary attachment, and intercostal tertiary veins. Cluster analysis revealed that they are grouped separately. However, the rank of C. liberica var. dewevrei cannot be decided yet until further taxonomic study, particularly on the anatomy and distribution pattern of domatia, is completed.

Short Communication: Investigation of leaf architectural patterns: Implications in delineating taxonomically controversial Hoya merrillii Schlechter and Hoya quinquenervia Warburg

Abstract. Paguntalan DP, Buot JrIE. 2019. Short Communication: Investigation of leaf architectural patterns: Implications in delineating taxonomically controversial Hoya merrillii Schlechter and Hoya quinquenervia Warburg. Biodiversitas 20: 833-839. Variations in leaf traits of two very likely similar plants, Hoya merrillii Schlechter and Hoya quinquenervia Warburg were examined together with an outgroup, Hoya cagayanensis Burton. The objectives of the study are to examine the leaf architectural characteristics of Hoya merrillii and Hoya quinquenervia and use the information as an additional basis of delineation between the said species of Hoya plants. Thirty leaf samples for each species were examined for laminal and vein characters. The characters laminar size, laminar shape, number of basal veins, quinternary vein fabric, areole development and characteristics of FEVs (free-ending veins), were well-defined from either one or both species. Overall, the results showed variability between the studied plant groups using univariate and multivariate analysis. The data ordination on the morphometric traits using PCOa showed distinct groupings among studied leaf samples and yielded consistent results with the single linkage or nearest neighbor cluster dendrogram which showed distinct clustering of individual species in terms of morphometric traits that were considered in the study. Detected variations of the leaf architectural traits on the leaves of Hoya merrillii Schlechter and Hoya quinquenervia Warburg allowed for the more available basis of separation in addition to established floral morphologies that are primarily used as criteria for delineation between species. Variations in leaf architecture characters can be of great value to illustrate or imply meanings in the taxonomic relationships of the Hoya species studied.

Delineation of the selected Cucumis L. species and accessions using leaf architecture characters

Abstract. Masungsong LA, Belarmino MM, Buot IEJr. 2019. Delineation of the selected Cucumis L. species and accessions using leaf architecture characters. Biodiversitas 20: 629-635. Regardless of the several attempts of the early and recent studies to separate the wild species of Cucumis from the cultivated ones, there is still taxonomic confusion brought about by the similarities in morphology of the genus. In a gene bank with so many species and accessions of Cucumis stored, it is appropriate to delineate these numerous accessions to save time and resources as well. This study aims to delineate fifty selected Cucumis accessions based on leaf architecture. Using Unweighted Pair Group Method using Averages (UPGMA) and Euclidean distance coefficient, a cluster analysis for the fifty Cucumis accessions was done. A dendogram with cophenetic coefficient of 0.9606 supported the clustering of the Cucumis species and accessions. At Eucledian distance of 1.5 two major clusters were formed on the basis of secondary vein spacing. Cucumis melo accessions separated from all the remaining accessions of C. myriocarpus, C. metuliferus, C. anguria and C. anguria var longaculeatus for having an increasing towards the base secondary vein spacing while the rest have irregular pattern of secondary vein spacing. Further sub-clustering of the remaining accessions comprising four species were delineated on the basis of tertiary vein (C. myriocarpus), tertiary vein angle to primary (C. metuliferus), and blade class (C. anguria and C. anguria var longaculeatus). Laminar shape delineated C. myriocarpus accessions from each other, apex angle for C. metuliferus accessions, and primary vein size for C. melo accessions. Results implied that leaf architecture is a good tool to classify the numerous accessions of Cucumis.

Species delineation of the genus Diplazium Swartz (Athyriaceae) using leaf architecture characters

The present study was conducted to delineate Diplazium Swartz species based on leaf architecture. Using PAleontological STatistics (PAST), a cluster and Principal Component Analysis of leaf architecture characters of 27 selected Diplazium species at the Philippine National Herbarium (PNH) was done. The dendogram (cophenetic correlation = 0.8436) and principal component analysis supported the four clusters of Diplazium using leaf architecture characters. At Gower distance of 0.25, Diplazium species were categorized as: Cluster 1 (Cladodromous – short stalked, stout and massive 1° vein); Cluster 2 (Reticulodromous – long stalked, moderate 1° vein); Cluster 3 (Craspedodromous – long stalked, stout to massive 1° vein); and Cluster 4 (Craspedodromous – short stalked, stout to massive 1° vein). The unifying characters were apex shape, base symmetry and 1° vein category, while the significant differentiating characters were 2° vein angle of divergence and variation in the 2° vein angle of divergence, 3° vein category, 3° vein angle of divergence, variation in 3° vein angle of divergence, 3° vein spacing and lobation. The successful delineation ofDiplazium species proved that leaf architecture can be a good taxonomic marker and could be an alternative way of identifying species in the absence of sori.

Foliar architecture of some members of the tribe Senecioneae (Asteraceae) with a key for identification of the Mexican genera

The foliar architecture of 18 genera (Barkleyanthus, Digitacalia, Erechtites, Nelsonianthus, Packera, Pentacalia, Pippenalia, Pittocaulon, Psacaliopsis, Psacalium, Pseudogynoxys, Robinsonecio, Roldana, Senecio, Telanthophora, Tetradymia, Villasenoria and Werneria) of the tribe Senecioneae (Asteraceae) distributed in Mexico is described. The aim was to identify leaf characters to be used in the taxonomy and phylogenetics of the tribe, as well as a source to identify at the generic rank the genera distributed in Mexico. More than 400 specimens were revised and several leaves were cleared to analyze leaf venation patterns. Four patterns of primary venation (actinodromous suprabasal, paralelodromous, pinnate and radiate-palmate) and five patterns of secondary venation (brochidodromous, weak-brochidodromous, craspedodromous, mixed-craspedodromous and festooned-semi-craspedodromous) were identified. Terminal tracheids were observed only in veinlets of Pentacalia, Pseudogynoxys and Werneria. In addition, secretory canals and crystals occurred in several genera. Foliar architecture showed to be a useful tool to identify genera, an identification key based mostly on leaf architecture characters is provided.

Mahonia fossils from the Oligocene of South China: Taxonomic and biogeographic implications

Mahonia is a genus with an East Asia-North America disjunct distribution today. Although Mahonia has a rich fossil record in North America dating back from Eocene to Miocene and some Oligocene to Pleistocene fossils from Europe, few fossils have been reported from East Asia. Here, three compressed fossil leaflets are described as a new species Mahonia ningmingensis Hu et Chen n. sp. from the Oligocene Ningming Formation in Guangxi, South China. This new fossil species shows leaf architectural characters of Group Orientales and has similarity with extant Mahonia bodinieri, Mahonia bealei, Mahonia breviracema, and Mahonia nittens. The leaf fossils described here represent the oldest records and lowest latitude occurrence of Mahonia in East Asia and reveal that the Group Orientales already existed in East Asia at least in the Oligocene. This record extends the stratigraphic range of Mahonia in East Asia and provides evidence for the hypothesis that migration of Mahonia between North America and East Asia might have taken place over both the North Atlantic Land Bridge and Bering Land Bridge.

Leaf architecture characters of Vachellia tortilis (Forssk.) Galasso and Banfi along longitudinal gradient in Limpopo Province, South Africa

This paper looked at the leaf architecture characteristics of Vachellia tortilis to determine if either there is or not an effect of the tropic line on plants. Vachellia tortilis leaves were sampled along a national road (N1) in Limpopo province. Sampling points were set 10 km apart away from the Tropic of Capricon in opposite directions. Leaf morphology revealed that leaves of V. tortilis are bipinnately compound with alternate arrangement. The venation pattern of the pinnules was eucamptodromus and brochidodromous with imperfect reticulation. Areoles were imperfect and pentagonal or irregular in shape.

Phylogenetic Analysis of Fossil Water Lilies Based on Leaf Architecture and Vegetative Characters: Testing Phylogenetic Hypotheses from Molecular Studies

Understanding the phylogenetic diversification of the water lilies (Nymphaeales sensu lato) in deep time is currently on the rise through studies based on both molecular analyses and the fossil record. An enhanced data set of leaf architectural and vegetative characters, for example, was found to be in broad agreement with phylogenies based only on molecular characters. Yet questions remain open regarding the relationships among the genera and subgenera of Nymphaea, the minimum time of divergence of familial and subfamilial clades and the phylogenetic radiation of the nymphaeoids during the Cenozoic that led to the living genera. Here we build on the aforementioned enhanced data set by adding a suite of nine, new or previously studied, Early to Late Cretaceous and Cenozoic fossil leaves to elucidate the phylogenetic positions of the fossil taxa, to test hypotheses based on molecular studies and to resolve phylogenetic relationships within Nymphaeales. In our phylogenetic analysis, five fossil leaf species show strong relationships with Nymphaeaceae and weaker subfamilial relationships to Nymphaea subgenus Lotos and to the Victoria—Euryale clade. Three fossil leaf species have strong relationships to Cabombaceae and are stem taxa. Taken as a whole, these new phylogenetic analyses yield strong evidence for the monophyly of the living families and some subfamilial clades. They also provide support for a divergence of Cabombaceae and Nymphaeceae by the Early Cretaceous. Finally, they suggest that some subfamilial clades of Nymphaeaceae may have originated by the Albian—Cenomanian, at the time of rapid diversification of the early angiosperms.

High diversity of Lauraceae from the Oligocene of Ningming, South China

Lauraceae is among the largest and floristically most important woody plant families in subtropical and tropical zones. However, the Cenozoic fossil records of Lauraceae are mostly from mid-latitude regions. Here we described eight lauraceous species from the Oligocene of Ningming, Guangxi, South China on the basis of leaf compressions with cuticular structure, providing new evidence for high diversity of Lauraceae in the low latitude region of the northern hemisphere during the late Paleogene. The extant genera to which the Ningming Oligocene fossils are possibly closely related include Cinnamomum, Neolitsea, Litsea, Alseodaphne, Laurus, and Beilschmiedia. All of these extant genera except Laurus still exist in Guangxi today, whereas Laurus is currently distributed in the Mediterranean and adjacent regions. A cladistic analysis based on leaf architectural and leaf cuticular characters for Paleogene Lauraceae species in the world indicated a possible relationship between European and East Asian Paleogene species.

Species limits of the endemic genus Stemonoporus Thw. : leaf architecture answers

Stemonoporus Thw. is the most species-rich (27 species) endemic dipterocarp genus in Sri Lanka. All its members are categorized as highly threatened or threatened in the IUCN red data book. A recent study carried out in order to evaluate the species limits ofStemonoporus, further strengthened its position as the most species-rich endemic dipterocarp genus in Sri Lanka by further adding a new species and totaling the number to 27. A detailed study on leaf architecture was carried out in order to identify characters for field identification of these 27 species. Leaves were cleared and scored for characters. Twenty leaf architectural characters were identified, including leaf venation type, primary, secondary and tertiary veins, areoles and veinlets. A comprehensive description of leaf architecture for all the species was complied. A combined phylogenetic analysis with other morphological characters was performed. The simple, entire margined, spirally arranged leaves indicated a shared ancestry.Within the genus Stemonoporus, all 27 species are monophyletic and are supported by leaf architectural apomorphies.The leaf venation characters used during the previous works are indistinctly defined and during the present study, novel, strong and stable leaf architectural characters were identified for each of the species. These characters could play a crucial role in field identification of these highly threatened taxa.

Paleocene Malvaceae from northern South America and their biogeographical implications

The clade Bombacoideae + Malvoideae ('Malvatheca group' sensu Baum et al.) in Malvaceae comprises a mostly tropical lineage with derived taxa that now thrive in higher latitudes. The sparse fossil record, especially for Malvoideae, obscures interpretations of past distributions. We describe fossil leaves of Malvoideae from the middle-late Paleocene Cerrejón Formation in Colombia, which contains evidence for the earliest known neotropical rainforest. Fifty-six leaf compressions belonging to Malvaceae were collected from the Cerrejón Formation in northern Colombia. Leaf architectural characters were scored and optimized for 81 genera of Malvaceae. Synapomorphic characters and unique character combinations support natural affinities for the fossil leaves. Fossil pollen from the same formation was also assessed. Despite convergence of overall leaf architecture among many Malvaceae, Malvaciphyllum macondicus sp. nov. can be assigned to the clade Eumalvoideae because of distal and proximal bifurcations of the costal secondary and agrophic veins, a synapomorphy for this clade. The leaf compressions, the oldest fossils for Eumalvoideae, indicate a minimum divergence time of 58-60 Ma, older than existing estimates from molecular analyses of living species. The abundance of eumalvoid leaves and of bombacoid pollen in the midlate Paleocene of Colombia suggests that the Malvatheca group (Malvoideae + Bombacoideae) was already a common element in neotropical forests and does not support an Australasian origin for Eumalvoideae.

Leaf architecture, lignification, and tensile strength during vegetative phase change in Zea mays

Background and Aims: Leaf morphology, anatomy, degree of lignification, and tensile strength were studied during vegetative phase change in an inbred line of <em>Zea mays</em> (OH43 x W23) to determine factors that influence mechanical properties during development. Methods: Tensometer, light microscopy, histochemistry. Key results: Mature leaf length increased linearly with plant development, peaked at leaves 7 and 8 (corresponding to the onset of the adult phase) and then declined. Leaf width was stable for leaves 1 through 3, increased to leaf 7, remained stable to leaf 10, and then declined through leaf 13. Lamina thickness was highest for leaf 1 and decreased throughout development. Leaf failure load to width ratio and failure load to thickness ratio increased with development suggesting that changes in leaf morphology during development do not entirely account for increases in failure load. Histochemical analyses revealed that leaf tensile strength correlates with percent lignification and the onset of anatomical adult features at various developmental stages. Conclusions: These data demonstrate that in <em>Zea mays</em> lignification of the midrib parenchyma and epidermis may be directly correlated with increased tensile strength associated with phase change from juvenility to adulthood. Failure load and resultant tensile strength values are primarily determined by the percent tissue lignification and the appearance of leaf architectural characters that are associated with the transition from the juvenile to the adult phase. Increased mechanical stability that occurs during the phase transition from juvenility to adulthood may signify a fundamental change in strategy for an individual plant from rapid growth (survival) to reproduction.