Palmate Venation Research Articles

Increase in Absolute Leaf Water Content Tends to Keep Pace with That of Leaf Dry Mass—Evidence from Bamboo Plants

Leaves, as the most important photosynthetic organ of plants, are intimately associated with plant function and adaptation to environmental changes. The scaling relationship of the leaf dry mass (or the fresh mass) vs. leaf surface area has been referred to as “diminishing returns”, suggesting that the leaf area fails to increase in proportion to leaf dry mass (or fresh mass). However, previous studies used materials across different families, and there is lack of studies testing whether leaf fresh mass is proportional to the leaf dry mass for the species in the same family, and examining the influence of the scaling of leaf dry mass vs. fresh mass on two kinds of diminishing returns based on leaf dry mass and fresh mass. Bamboo plants (Poaceae: Bambusoideae) are good materials for doing such a study, which have astonishingly similar leaf shapes across species. Bamboo leaves have a typical parallel venation pattern. In general, a parallel venation pattern tends to produce a more stable symmetrical leaf shape than the pinnate and palmate venation patterns. The symmetrical parallel veins enable leaves to more regularly hold water, which is more likely to result in a proportional relationship between the leaf dry mass and absolute water content, which consequently determines whether the scaling exponent of the leaf dry mass vs. area is significantly different from (or the same as) that of the leaf fresh mass vs. area. In the present study, we used the data of 101 bamboo species, cultivars, forms and varieties (referred to as 101 (bamboo) taxa below for convenience) to analyze the scaling relationships between the leaf dry mass and area, and between leaf fresh mass and area. We found that the confidence intervals of the scaling exponents of the leaf fresh mass vs. dry mass of 68 out of the 101 taxa included unity, which indicates that for most bamboo species (67.3%), the increase in leaf water mass keeps pace with that of leaf dry mass. There was a significant scaling relationship between either leaf dry mass or fresh mass, and the leaf surface area for each studied species. We found that there was no significant difference between the scaling exponent of the leaf dry mass vs. leaf area and that of the leaf fresh mass vs. leaf area when the leaf dry mass was proportional to the leaf fresh mass. The goodness of fit to the linearized scaling relationship of the leaf fresh mass vs. area was better than that of the leaf dry mass vs. area for each of the 101 bamboo taxa. In addition, there were significant differences in the normalized constants of the leaf dry mass vs. fresh mass among the taxa (i.e., the differences in leaf water content), which implies the difference in the adaptabilities to different environments across the taxa.

Taxonomic and phylogenetic significance of leaf venation characteristics in Dioscorea plants

We undertook a comparative study of the leaf venation characteristics of Dioscorea species from all seven sections distributed in China (33 species, 1 subspecies and 3 varieties). We established that leaf venation has a taxonomic significance in Dioscorea . The sections Combili, Opsophyton Lasiophyton and Shannicorea all show consistent acrodromous venation (a subtype of palmate venation), with Botryosicyos exhibiting consistent pinnate venation. However, sections Stenophora and Enantiophyllum show obvious intrasectional differences. For example, D. simulans and D. biformifolia of section Stenophora have acrodromously veined middle leaflets, whereas the side leaflets are pinnately veined; D. cirrhosa and D. cirrhosa var. cylindrica of section Enantiophyllum show dichotomous veinlets. Other species in the same section show either one-branched veinlets or multiple branched veinlets. In addition to the discrepancy in venation patterns, differences in many other important morphological characteristics and chemical components were also observed. Therefore, D. simulans and D. biformifolia can be reasonably excluded from section Stenophora, and section Illigerestrum can be rebuilt using these two species. In addition, D. cirrhosa and D. cirrhosa var. cylindrica should be removed from section Enantiophyllum and placed into another new section. D. simulans and D. biformifolia show pinnate venation, and the complexity of their leaf organization (with both simple and compound leaves) also points to variations between the pinnate and acrodromous veins in Dioscorea . The repeated presence of palmate and pinnate venation in multiple angiosperm clades also suggests that the formation and evolution of venation are likely the result of evolutionary adaptation to ecological environments. https://doi.org/10.2298/ABS170322058S Received: March 22, 2017; Revised: August 24, 2017; Accepted: August 24, 2017; Published online: December 26, 2017 How to cite this article: Sun X, Xue J, Lei Z, Li M, Zhang Y, Zhou G, Hang Y. Taxonomic and phylogenetic significance of leaf venation characteristics in Dioscorea plants. Arch Biol Sci. 2018;70(2):397-407.

English

Strychnos spinosa Lam. belongs to the family Loganiaceae.  It is a small tree.  The morphological and anatomical features of the leaves, stem, flower and fruit were studied. S. spinosa has a cylindrical stem with a pair of spines at irregular spaces. The leaves are opposite, decussate, petiolate with palmate venation. The petals are greenish in colour, tubular with five lobes. There are numerous white hair-like appendages at the neck of the corolla tube. The androecium is epipetalous and attached close to the bottom of the corolla tube. The flower is a cyme, occurring in threes, with the middle one being the oldest. The fruit is a berry with very hard pericarp. It turns from light green when unripe to bright yellow when ripe. The anatomy of the leaf revealed presence of rosette crystals and intraxylary phloem which is more pronounced in the mid rib and petiole. “Kranz” structure was observed in the transverse section of the leaf. Anisocytic stomata are numerous in the abaxial (lower) epidemis but absent in the adaxial epidemis. The anatomy of the stem showed the presence of crystals in the cortex. Both solitary and multiple vessels are found in the transverse section.  In the tangential longitudinal section, most of the rays were four to seven cells wide, but a few were uniseriate, biseriate and triseriate. Most of the pollen grains were triangular in the polar view but a few were quadrangular. Those that were triangular exhibited tricolporate aperture while those that were quadrangular had tetracolporate aperture. The sculpturing was perforate and were not very compact.   Key words: Strychnos spinosa, rosette crystals, intraxylary phloem, pollen dimorphism, heterogenous, rays.

A new species of Chamaecrista sect. Chamaecrista ser. Flexuosae (Leguminosae, Caesalpinioideae) from Serra do Cipó, Minas Gerais, Brazil

A new species, Chamaecrista truncata, from southeastern Brazil, is described, illustrated and compared to its putative closest relative, C. parvistipula. The new species belongs to Chamaecrista sect. Chamaecrista ser. Flexuosae which is characterized by asymmetrical leaflets with palmate venation, quadrangular stems and axillary peduncles. Additionally, the venation pattern of the leaflets and the different types of stipules observed within this series are shown.

KNOX overexpression in transgenic Kohleria (Gesneriaceae) prolongs the activity of proximal leaf blastozones and drastically alters segment fate

KNOX (knotted1-like homeobox) genes have a widely conserved role in the generation of dissected leaves. Ectopic KNOX activity in leaves in various angiosperm lineages causes leaf form changes that can elucidate how the configuration of leaf development evolved. We present an analysis of leaf morphology and morphogenesis in transgenic Kohleria lines overexpressing a heterologous KNOX gene. Kohleria, like many members of Gesneriaceae, has simple-serrated leaves with pinnate venation. KNOX overexpression causes prolonged segment proliferation in proximal, but not distal, parts of leaf blades. Elaborate dissected segments reiterate the zonation of the whole leaf, with organogenic activity persisting between a distal maturation zone and a proximal intercalary elongation zone. The architecture of vascular bundles is severely altered, with a reduced midvein and a more palmate venation. The initial establishment of organogenically competent primordial margins (marginal blastozones) and the onset of tissue differentiation in early stages of leaf development were similar in wild-type and KNOX overexpressing lines. However, leaves overexpressing KNOX often failed to fully mature, and persistent marginal blastozones were found at the base of blades in mature portions of the shoot. We conclude that KNOX-mediated perpetuation of marginal blastozones in Kohleria is sufficient to induce a set of processes that result in highly dissected leaflets, which are unusual in this plant family. Spatial confinement of blastozones between an early maturing tip and a late elongating petiole zone reflects the presence of distinct maturation processes that limit the ability of the leaf margins to respond to ectopic KNOX gene expression.

Scutifolium jordanicumgen. et sp. nov. (Cabombaceae), an aquatic fossil plant from the Lower Cretaceous of Jordan, and the relationships of related leaf fossils to living genera

A new species of aquatic plant, Scutifolium jordanicum gen. et sp. nov., Taylor, Brenner & Basha, is described from the Albian of Jordan. The leaves are microphyllous with a symmetrical, elliptical to suborbiculate shape, convex to rounded apex and base, and actinodromous to palinactinodromous primary venation. The peltate, centrally attached petioles are narrow, elongate, and alternately arranged on similarly sized stems. The leaves appear to be thick and have aerenchyma. Comparisons to plants with centrally peltate leaves and palmate venation and to aquatic plants with floating leaves suggest that S. jordanicum belongs to the Cabombaceae lineage within the Nymphaeales. Cladistic analysis including the fossil and living members of the Nymphaeales shows that the S. jordanicum is basal to the living members of the family and has unique characters not found in any living genera. This is the oldest evidence of the Cabombaceae from the Old World. Inclusion of two other Early Cretaceous peltate leaf fossils in the phylogenetic analysis indicates their affinities to Cabombaceae and that some of the shared derived characters for the living members are progressively acquired in the fossils. These data show the Cabombaceae were widespread in Gondwana and Laurasia by the mid-Cretaceous.

Leaf palmate venation and vascular redundancy confer tolerance of hydraulic disruption.

Leaf venation is a showcase of plant diversity, ranging from the grid-like network in grasses, to a wide variety of dendritic systems in other angiosperms. A principal function of the venation is to deliver water; however, a hydraulic significance has never been demonstrated for contrasting major venation architectures, including the most basic dichotomy, "pinnate" and "palmate" systems. We hypothesized that vascular redundancy confers tolerance of vein breakage such as would occur during mechanical or insect damage. We subjected leaves of woody angiosperms of contrasting venation architecture to severing treatments in vivo, and, after wounds healed, made detailed measurements of physiological performance relative to control leaves. When the midrib was severed near the leaf base, the pinnately veined leaves declined strongly in leaf hydraulic conductance, stomatal conductance, and photosynthetic rate, whereas palmately veined leaves were minimally affected. Across all of the species examined, a higher density of primary veins predicted tolerance of midrib damage. This benefit for palmate venation is consistent with its repeated evolution and its biogeographic and habitat distribution. All leaves tested showed complete tolerance of damage to second- and higher-order veins, demonstrating that the parallel flow paths provided by the redundant, reticulate minor vein network protect the leaf from the impact of hydraulic disruption. These findings point to a hydraulic explanation for the diversification of low-order vein architecture and the commonness of reticulate, hierarchical leaf venation. These structures suggest roles for both economic constraints and risk tolerance in shaping leaf morphology during 130 million years of flowering plant evolution.

Overexpression of a knotted-like homeobox gene of potato alters vegetative development by decreasing gibberellin accumulation.

Potato (Solanum tuberosum) homeobox 1 (POTH1) is a class I homeobox gene isolated from an early-stage tuber cDNA library. The RNA expression pattern of POTH1, unlike that of most other class I knotted-like homeobox genes, is widespread in the cells of both indeterminate and differentiated tissues. Using in situ hybridization, POTH1 transcripts were detected in meristematic cells, leaf primordia, and the vascular procambium of the young stem. Overexpression of POTH1 produced dwarf plants with altered leaf morphology. Leaves were reduced in size and displayed a "mouse-ear" phenotype. The mid-vein was less prominent, resulting in a palmate venation pattern. The overall plant height of overexpression lines was reduced due to a decrease in internode length. Levels of intermediates in the gibberellin (GA) biosynthetic pathway were altered, and the bioactive GA, GA(1), was reduced by one-half in sense mutants. Accumulation of mRNA for GA 20-oxidase1, a key biosynthetic enzyme, decreased in overexpression lines. In vitro tuberization was enhanced under both short- and long-day photoperiods in several POTH1 overexpression lines. Sense lines produced more tubers at a faster rate than controls. These results imply that POTH1 mediates the development of potato by acting as a negative regulator of GA biosynthesis.

Early Permian palaeofloras from southern brazilian Gondwana: a Palaeoclimatic approach

In evaluating the parameters supplied by the taphofloras from different sedimentary facies in the Early Permian sedimentary sequences of the southern part of the Parana basin, Brazil, it has become evident that the palaeofloristic evolution was related to palaeoecological and palaeoclimatic evolution. The homogeneous composition of Early Permian floral assemblages, which are characterized mainly by herbaceous to shrub-like plants considered to be relicts from the rigorous climate of an ice age (e.g. Botrychiopsis plantiana) suggest the persistence of the cold climate. The dominance of Rubidgea and Gangamopteris leaves with palmate venation associated with glossopterids with penate venation seems to indicate a gradual warming of climate. In roof-shales of coalbearing strata pinnate glossopterids related to are common, while Gangamopteris and Rubidgea (palmate forms) are poorly represented. The sudden enrichment of herbaceous articulates and filicoids fronds is characteristic of this stage and trunks of arborescents lycophytes become important elements. These antrocophilic paleofloras are characterized by typical elements of the Glossopteris flora associated to tree lycophytes and ferns communities. Therefore, the cool seasonal climate of Early Permian changed into the moist seasonal interval during the Artinskian-Kungurian. This climatic change was significant to the meso-hygrophitic to hygrophitic vegetation registered in roof-shale ferns of the Gondwana Southern Brazilian coalbearing strata.

EARLY PERMIAN PALAEOFLORAS FROM SOUTHERN BRAZILIAN GONDWANA: A PALAEOCLIMATIC APPROACH

In evaluating the parameters supplied by the taphofloras from different sedimentary facies in the Early Permian sedimentary sequences of the southern part of the Paraná basin, Brazil, it has become evident that the palaeofloristic evolution was related to palaeoecological and palaeoclimatic evolution. The homogeneous composition of Early Permian floral assemblages, which are characterized mainly by herbaceous to shrub-like plants considered to be relicts from the rigorous climate of an ice age (e.g. Botrychiopsis plantiana) suggest the persistence of the cold climate. The dominance of Rubidgea and Gangamopteris leaves with palmate venation associated with glossopterids with penate venation seems to indicate a gradual warming of climate. In roof-shales of coalbearing strata pinnate glossopterids related to Glossopteris are common, while Gangamopteris and Rubidgea (palmate forms) are poorly represented. The sudden enrichment of herbaceous articulates and filicoids fronds is characteristic of this stage and trunks of arborescents lycophytes become important elements. These antrocophilic paleofloras are characterized by typical elements of the "Glossopteris flora" associated to tree lycophytes and ferns communities. Therefore, the cool seasonal climate of Early Permian changed into the moist seasonal interval during the Artinskian-Kungurian. This climatic change was significant to the meso-hygrophitic to hygrophitic vegetation registered in roof-shale ferns of the Gondwana Southern Brazilian coalbearing strata.

Secondary and Tertiary Pulvini in the Unifoliate Leaf of Cercis canadensis L. (Fabaceae) with Comparison to Bauhinia purpurea L.

There are three leaf types in the Cercideae tribe (Caesalpinioideae, Fabaceae): unifoliate, bilobate, and bifoliate. By the fusion hypothesis, the ancestral leaf type within the Cercideae was bifoliate, and the unifoliate leaf was derived from the fusion of the bifoliate leaflets. In the opposing splitter hypothesis, the unifoliate leaf was the ancestral leaf type within the Cercideae, and the bifoliolate leaf was derived from the splitting of the unifoliate leaf into two separate leaflets. Palmate venation in leaflets is problematic for the fusion hypothesis. Watari proposed derivation from a palmately compound leaf with many leaflets and interpreted the primary vein as homologous to a single midrib in a leaflet. The structure and function of the upper pulvinus in the unifoliate leaf of Cercis canadensis L. were examined to test the two hypotheses. Microscopic observations and measurement of leaf movement over a 12‐h period indicate that the upper pulvinus in the unifoliate leaf is a compound structure consisting of an apical common joint composed of three secondary pulvini and two lateral laminar joints separated by a laminar joint associated with the midrib. A lateral laminar joint consists of three tertiary pulvini, one at the base of each primary vein, and the midrib is formed from a rachilla and two or more pinnules. Structure comparisons were made between the upper pulvinus of a unifoliate leaf of C. canadensis and a bilobate leaf of Bauhinia purpurea. The secondary and tertiary nature of the upper pulvinus indicates that the unifoliate leaf in Cercis was derived from an extinct ancestor with bipinnately compound leaves. Results add support for Watari’s interpretation of the primary vein and for the splitter hypothesis.

Apparition de l'asymétrie foliaire chez les plantules du Begonia subvillosa et du B. fagifolia (Begoniaceae)

The leaves of the majority of Begonia species are asymmetrical. To shed some light on the nature of this asymmetry, the authors followed the development of the first forming leaves in two species with very different adult shapes: Begonia subvillosa, which has strongly asymmetrical leaves and palmate venation, and B. fagifolia, which has pinnate venation and symmetrical leaves. Key stages of the development were identified. First, there is no asymmetry within the embryo. In both species, the leaves of the first two nodes are asymmetrical in the early stages. However, they lose this asymmetry during development and show a palmate venation. From the third node on, the two species show some differences. The leaf of B. subvillosa keeps its initial asymmetry and part of its blade develops into an auricle, unlike the leaf of B. fagifolia. From the fourth node on, the leaf of B. fagifolia is pinnately veined. The central area of the leaf blade of both species settles to its adult shape much earlier in development than other areas of the leaf. The different parts of the blade acquire their adult characteristics successively according to different timing sequences. Key words: Begoniaceae, development, leaf, morphogenesis, symmetry.

西表島の特異なフウトウカズラ個体群

Taxon of Piper species was difficult in taxonomy and ecology. We investigated species biological populations of Piper in Southeast Asia and South Pacific areas. A new variant of Piper kadsura was found in Iriomote Island, Okinawa. In Japan, P. kadsura is distributed from Kanto (Chiba) to Okinawa and grows in the forest along the sea coast. Forty eight samples taken between Chiba and Ryukyu Islands were used. The samples were examined and compared for their leaf-form, inflorescense, pollen ornamentation and isozyme patterns. Result showed that the leaf-form of Shirahama and Haimida-hama populations in Iriomote Island was ovate, entire with acute apex, cordate base, palmate venation and sharp tip pollen ornamentation than those from other populations having flat top pollen ornamentation. Moreover, isozyme pattern was found different from other populations sampled. Its morphological characteristics were not similar to P. kadsura . Hence, it is assumed that Shirahama and Haimida-hama populations were variants of P. kadsura.

Inflorescence Bracts of Fossil and Extant Tilia in North America, Europe, and Asia: Patterns of Morphologic Divergence and Biogeographic History

The enlarged inflorescence bract diagnostic of extant Tilia has an extensive Tertiary fossil record in the Northern Hemisphere. Diversity of bract morphology, and the extent of adnation between peduncle and bract, is reviewed for fossil and extant species of Tilia. An extinct type of bract with an orbicular outline and palmate venation is documented by the fossil species Tilia circularis (Chaney) comb. nov. from the early Oligocene of Oregon and is designated Type A. Living species of the genus have elongate bracts with predominately pinnate venation that are borne in two basic configurations: Type B, with the peduncle fused only to the extreme base of the bract lamina, as in extant Tilia endochrysea Hand.-Mzt. of southern China; and Type C with the peduncle fused medially along the basal one-third of the bract lamina, as in most extant species. Bracts of Type B were widely distributed in the Tertiary of western North America (late Eocene to Miocene) and Europe (early Miocene to Pliocene), while those of Type C are known in the fossil condition only from the middle and late Tertiary of Asia and Pliocene of Europe. The bracts of T. circularis, like those of type B, are borne on relatively long stalks and have the peduncle fused only at the extreme base. The fossil record supports recognition of the following characters as apomorphic in Tilia bract evolution: bracts sessile, peduncle adnate to the upper surface of the bract, and pinnate bract venation.

Inflorescence bracts of fossil and extant Tilia in North America, Europe, and Asia: patterns of morphologic divergence and biogeographic history

The enlarged inflorescence bract diagnostic of extant Tilia has an extensive Tertiary fossil record in the Northern Hemisphere. Diversity of bract morphology, and the extent of adnation between peduncle and bract, is reviewed for fossil and extant species of Tilia. An extinct type of bract with an orbicular outline and palmate venation is documented by the fossil species Tilia circularis (Chaney) comb. nov. from the early Oligocene of Oregon and is designated Type A. Living species of the genus have elongate bracts with predominately pinnate venation that are borne in two basic configurations: Type B, with the peduncle fused only to the extreme base of the bract lamina, as in extant Tilia endochrysea Hand.‐Mzt. of southern China; and Type C with the peduncle fused medially along the basal one‐third of the bract lamina, as in most extant species. Bracts of Type B were widely distributed in the Tertiary of western North America (late Eocene to Miocene) and Europe (early Miocene to Pliocene), while those of Type C are known in the fossil condition only from the middle and late Tertiary of Asia and Pliocene of Europe. The bracts of T. circularis, like those of type B, are borne on relatively long stalks and have the peduncle fused only at the extreme base. The fossil record supports recognition of the following characters as apomorphic in Tilia bract evolution: bracts sessile, peduncle adnate to the upper surface of the bract, and pinnate bract venation.

Vegetative Anatomy of Cultivated Grapes--A Review

The anatomy of vegetative structures of cultivated grapevines, as described in selected literature, is presented, with emphasis on development of established vines of <i>Vitis vinifera</i>. Other topics briefly considered are the anatomy of propagules, muscadine grapes, tetraploid vines, phylloxera galls, mineral-deficient vines, and injury of leaves by ozone and 2,4-D. The terms used to describe grapevine morphology and anatomy are defined in a glossary. A growing root shows zones of cell division, cell elongation, and tissue differentiation. Vascular structure is similar in the root and the stem, although the mitotic activity of vascular and cork cambia is more irregular. Root cortex is often invaded by endotrophic mycorrhiza. The stem primary vascular system is composed of leaf, bud, and tendril traces. Procambium and phloem differentiate acropetally, and xylem differentiates in both directions from the nodes. During the first growing season of the stem, a cambium produces secondary xylem and phloem and extends rays. Xylem consists of large scalariform vessels surrounded by thick-walled pitted parenchyma and large masses of living septate fibers. Phloem consists of blocks of living septate fibers alternating with blocks of sieve elements, companion cells, and parenchyma. Ray cells are pitted and thick-walled in the xylem but thin-walled in the phloem. Cells of the stem and root store starch, which is greatly depleted when shoots begin to grow in the spring. Phellogen forms from the living cells of the nonconducting primary phloem in the first year in stems of <i>Euvitis</i> Planch. (in the subepidermal layer in <i>Muscadinia</i> Planch.), and then successively each year in the nonconducting secondary phloem. It cuts off all the tissues lying outside of it, and these are shed with the periderm. In spring, sieve elements formed the previous year are revitalized and function as conduits until new sieve elements are formed from the cambium. Each foliage leaf on a growing shoot has a precocious axillary bud consisting of a single prophyll and a variable number of leaves. This develops into the summer lateral branch. The four vascular traces of this axillary bud diverge from the traces of the subjacent tendril or bud, not from those of the subtending leaf. The bud in the prophyll of the summer lateral develops into the primary bud with 2-3 prophylls, a few leaves, and then several leaves opposed by clusters or tendrils in a generally regular pattern. Formed in the axils of the two basal prophylls of the primary shoot are the secondary and tertiary buds, respectively. These three buds, surrounded by the prophyll of the summer lateral, enter dormancy at the end of the growing season and constitute the compound bud or eye of the mature cane. The next season the primary bud develops into the fruiting shoot. The secondary and tertiary buds may develop into shoots or remain latent for extended periods. A tendril arises as a primordium on the apical meristem opposite that of a leaf. Two of its vascular traces are connected with those of the bud below it, and two with those of the leaf above it. It functions first as a hydathode and later as a twining organ. At each node, five traces to the leaf leave the ring of stem vascular bundles through separate gaps. The traces divide and anastomose to form the complicated network of palmate venation in the leaf, each tooth ending in a hydathode. Blade tissues of a mature leaf, which are differentiated from six layers of meristematic cells, comprise the upper epidermis, one layer of palisade cells, three layers of spongy mesophyll cells, and the lower epidermis with stomates.