Species Of Woody Dicotyledons Research Articles

Should the relationship between leaf margin and temperature be re‐defined for areas with colder climates?

AbstractAimThe well‐proven positive correlation between the increased proportion of entire‐leaved woody dicotyledonous species and increased mean annual temperature has been commonly used to estimate temperature in the past. However, in regions of colder climates, this relationship is not straightforward, questioning the accuracy of temperature estimation.LocationFinland, Poland, Germany.TaxonDicotyledons.MethodsThe floristic composition of 10 × 10 km squares in 20 km wide transects through Finland, Poland and Germany was analysed.ResultsAt higher temperatures, deciduous woody plants appeared to show the expected positive relationship between mean annual temperature and the proportion of entire leaf margins. However, we found a negative correlation within woody deciduous plants at higher latitudes with mean annual temperature values from approximately −2.5°C to +2–4°C and at all temperatures when all woody plants were included. Herbaceous species showed a weak relationship between morphology and temperature.Main ConclusionsThe hypothesis that the phenomenon was caused by a large percentage of entire‐leaved evergreen species that winter under snow cover was rejected. These results indicate that using the leaf margin analysis method for past temperature estimation is increasingly inaccurate at colder temperatures. Consequently, we recommend avoiding this method at locations where the mean annual temperature falls below 5°C.

LEAF MARGIN ANALYSIS: A NEW EQUATION FROM HUMID TO MESIC FORESTS IN CHINA

Leaf margin analysis (LMA) is a widely used method that applies present-day linear correlation between the proportion of woody dicotyledonous species with untoothed leaves (P) and mean annual temperature (MAT) to estimate paleotemperatures from fossil leaf floras. Previous works demonstrate that LMA shows regional constraints and to date, no equation has been modeled directly from Chinese forests. Fifty humid to mesic Chinese forests were chosen to understand the relationship between percentage of untoothed leaf species and MAT in China. Consistent with previous studies, the Chinese data indicate that P shows a strong linear correlation with MAT, but the actual relationship is a little different from those recognized from other regions. Among the several currently used LMA equations, the one resulting from North and Central American and Japanese data, rather than the widely used East Asian LMA equation, yields the closest values to the actual MATs of the Chinese samples (mean absolute error = 1.9 degrees C). A new equation derived from the Chinese forests is therefore developed, where MAT = 1.038 + 27.6 x P. This study not only demonstrates the similarity of the relationship between P and MAT in the Northern Hemisphere, but also improves the reliability of LMA for paleoclimate reconstructions of Chinese paleofloras.

Phytolith analysis of selected native plants and modern soils from southeastern Uruguay and its implications for paleoenvironmental and archeological reconstruction

This paper presents a phytolith analysis of selected native plants and modern surface soils from southeastern Uruguay. A modern phytolith reference collection was established based on 60 Poaceae species, 22 non-Poaceae monocotyledonous species, 17 species of herbaceous dicotyledons, 9 woody dicotyledonous species, and 2 species of fern. Nine modern surface soil samples were analyzed from the most representative vegetation units of the region, including wetlands, wet prairies, upland prairies, riparian forest, and palm forest. Of the 50 non-Poaceae plant species analyzed, 25 contribute diagnostic phytoliths at different taxonomic levels corresponding to all the major ecological zones of southeastern Uruguay. Patterns of phytolith production and morphology were concordant with those observed in related taxa studied from other regions of the world. The modern soil analysis revealed significant patterns that differentiate a number of specific habitats, showing that distinct vegetational units may be discriminated by the phytolith signatures they produce. These results reinforce the utility of using phytoliths as significant indicators for vegetation units dominated both by monocotyledonous and dicotyledonous plant species, and demonstrate the potential of phytolith analysis for paleoecological and archeological reconstruction in this region.

Do leaf margins of the temperate forest flora of southern South America reflect a warmer past?

ABSTRACTAim Our aims were: (1) to characterize the linear relationship between the proportion of woody dicotyledonous species with entire‐margined leaves (E) and mean annual temperature (MAT) from a southern temperate flora that still harbours many lineages that originated under warmer climates; (2) to compare this relationship with those developed from floras of different regions of the world; and (3) to contrast temperature predictions based on leaf margins of the native southern flora versus the naturalized alien flora, mostly of boreal origin.Location The temperate forest of southern South America (TFSA).Methods At each 1° latitudinal band, we estimated E based on species latitudinal ranges and MAT from both an isotherm map and a global temperature grid. We also calculated E from five local floras located between 40 and 43° S, and from the naturalized alien flora of Nahuel Huapi National Park in southern Argentina.Results We found a close relationship between E and MAT for the TFSA. Equations developed from floras of the Northern Hemisphere overestimated extant temperatures of this biome by 6–10 °C at both geographical and local spatial scales. On the other hand, MAT predictions from leaf margins of the alien flora were similar to the actual MAT. A published regression between E and MAT from tropical South America was remarkably similar to the one we estimated from the TFSA. This tropical equation predicted accurately the temperatures observed for this temperate biome based on leaf margins of the native flora.Main conclusions Despite massive plant extinction due to environmental cooling and biogeographical isolation during the Tertiary, leaf‐margin analysis reveals that the flora of the TFSA still reflects its original development under the warmer conditions of western Gondwana and its past connections with low‐latitude forest floras of tropical South America.

Bordered pits in ray cells and axial parenchyma: the histology of conduction, storage, and strength in living wood cells

Bordered pits occur in walls of living ray cells of numerous species of woody dicotyledons. The occurrence of this feature has been minimally reported because the pits are relatively small and not easily observed in face view. Bordered pits are illustrated in sectional view with light microscopy and with scanning electron microscopy in face view for dicotyledonous and gnetalean woods. Bordered pits are more numerous and often have prominent borders on tangential walls of procumbent ray cells, but also occur on radial walls; they are approximately equally abundant on tangential and horizontal walls of upright cells, suggesting parallels to cell shape in flow pathway design. Axial parenchyma typically has secondary walls thinner than those of ray cells, but bordered pits or large simple pit areas occur on some cross walls of parenchyma strands. There is no apparent correlation between the phylogenetic position of species and the presence of borders in ray cells or axial parenchyma. Bordered pits represent a compromise between maximal mechanical strength and maximal conductive capability. High rates of flow of sugar solutions may occur if starch in ray cells or axial parenchyma is mobilized for sudden osmotic enhancement of the conductive stream or for rapid development of foliage, flowers, or fruits. Measurement of the secondary wall thickness of ray cells may offer simple inferential information about the role that rays play in the mechanical strength of woods.

The leaf size – twig size spectrum and its relationship to other important spectra of variation among species

There is a spectrum from species with narrow, frequently branched twigs carrying small leaves and other appendages, to species with thick twigs carrying large leaves and appendages. Here we investigate the allometry of this spectrum and its relationship to two other important spectra of ecological variation between species, the seed mass-seed output spectrum and the specific leaf area-leaf lifespan spectrum. Our main dataset covered 33 woody dicotyledonous species in sclerophyll fire-prone vegetation on low nutrient soil at 1,200 mm annual rainfall near Sydney, Australia. These were phylogenetically selected to contribute 32 evolutionary divergences. Two smaller datasets, from 390 mm annual rainfall, were also examined to assess generality of cross-species patterns. There was two to three orders of magnitude variation in twig cross-sectional area, individual leaf size and total leaf area supported on a twig across the study species. As expected, species with thicker twigs had larger leaves and branched less often than species with thin twigs. Total leaf area supported on a twig was mainly driven by leaf size rather than by the number of leaves. Total leaf area was strongly correlated with twig cross-section area, both across present-day species and across evolutionary divergences. The common log-log slope of 1.45 was significantly steeper than 1. Thus on average, species with tenfold larger leaves supported about threefold more leaf area per twig cross-section, which must have considerable implications for other aspects of water relations. Species at the low rainfall site on loamy sand supported about half as much leaf area, at a given twig cross-section, as species at the low rainfall site on light clay, or at the high rainfall site. Within sites, leaf and twig size were positively correlated with seed mass, and negatively correlated with specific leaf area. Identifying and understanding leading spectra of ecological variation among species is an important challenge for plant ecology. The seed mass-seed output and specific leaf area-leaf lifespan spectra are each underpinned by a single, comprehensible trade-off and their consequences are fairly well understood. The leaf-size-twig-size spectrum has obvious consequences for the texture of canopies, but we are only just beginning to understand the costs and benefits of large versus small leaf and twig size.

Storied Structure of the Secondary Phloem

The anatomy of the secondary phloem with a storied structure of 49 species of woody dicotyledons from the Ivory Coast, West Africa, has been studied. They belong to the families Bixaceae (1 species), Bombacaceae (3 species), Caesalpiniaceae (4 species), Papilionaceae (18 species), Sterculiaceae (16 species), and Tiliaceae (7 species). In the Bixaceae and Sterculiaceae only the axial system is storied whereas in the four other families usually both the ray and axial systems are storied.

Dependence of Photosynthetic Rates on Leaf Density Thickness in Deciduous Woody Plants Grown in Sun and Shade

Comparisons of photosynthetic rates were made on leaves of ten species of woody dicotyledons grown in the field under full sun or under a canopy which transmitted approximately 18% of full light. Photosynthesis and dark respiration were measured and compared on various bases: area, chlorophyll, fresh weight of lamina, density thickness (fresh weight per unit area), and protein.Light-saturated photosynthesis per unit area or unit chlorophyll was about 1.5 times greater in the sun leaves than in the shade leaves and essentially equal per unit fresh weight or unit protein. Sun leaves were thicker but the enzymes per unit fresh weight remained constant as thickness varied. Chlorophyll per unit area remained about constant; chlorophyll per unit fresh weight varied inversely with changes in leaf thickness. Thus, density thickness variation is important in photosynthetic adaptation to sun and shade. This is also shown by the relationship between light-saturated photosynthesis per unit area and density thickness.

COMPARATIVE STUDY OF THE SECONDARY PHLOEM OF SOME WOODY DICOTYLEDONS

SUMMARY The anatomical features of the secondary phloem of 444 species of woody dicotyledons, belonging to 24 families, all from the Ivory Coast, West-Africa, were used to find correlations among the different types of secondary phloem characteristics as indicated by Zahur (1959). Special attention is given to companion cells since according to Zahur (1959), the type is fairly constant for natural categories. A reinvestigation of Zahurs data also revealed some correlations not noticed by him. In the axial system of the secondary phloem of the investigated species both a primitive companion-cell type (type A) and in less extent a primitive sieve-tube type (type I) are associated and therefore correlated with an advanced axial-parenchyma type (type +) and mechanical-tissue type (type 1). Also the reverse correlation is present. A correlation between a primitive companion-cell type and a primitive sieve-area type (type a) as one could conclude from Zahurs data, is not present in our material. Also the correlation between an advanced companion-cell type (type C) and an advanced sieve-area type (type c), is difficult to ascertain or entirely absent. The above described correlation is less evident or even absent in those species in which a primitive sieve-tube type (type I) is present together with an advanced companion-cell type (type C) and in those species in which an advanced sieve-tube type (type III) is present together with a primitive companion-cell type (type A). In the secondary phloem of the concerned species from the Ivory Coast this is rather often the case. If a storied structure is present sieve-tube type III occurs associated with companion-cell type C (and B). Such a combination of the two factors clearly indicates a primitive axial-parenchyma type (type -) and mechanical-tissue type (type 3), since both factors point in the same direction.

The Control of Leaf Morphology and the Tolerance of Shade by Woody Plants

We compared the rates of stem growth and leaf area per plant of 10 woody dicotyledonous species in full sun and under an artificial shade transmitting about 18% light and did not find any correlation with tolerance to shade (silvicultural classification). Cottonwood, the most intolerant species, grew rapidly in the shade for two seasons but died during the third. The reduction in the shade of leaf thickness (density thickness, measured as fresh weight per unit area) varied between species but did not correlate with tolerance. However, the product of the density thickness and the leaf area (fresh weight per leaf-lamina) was reduced (60%) in the shade much more in the three least tolerant species (cottonwood, catalpa, and American plum) than in the seven more tolerant species (20%). This may be a consequence of shade avoidance by the intolerant species, reducing the net photosynthate available per leaf.

Lateral sieve-area pores in woody dicotyledons

The secondary phloem of seven species of woody dicotyledons (Populus deltoides, Quercus alba, Rhus glabra, Robinia pseudoacacia, Salix nigra, Tilia americana, and Ulmus americana) was fixed in glutaraldehyde and in formaldehyde–glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. The pores of the lateral sieve areas are essentially similar in structure to those of the sieve plates, with the exception that many of the lateral sieve-area pores contain median nodules at maturity. In addition, some pore groups in Rhus, Robinia, and Tilia are associated with median cavities, median enlargements arising through the union of two or more median nodules, similar to those associated with the sieve areas of conifers. The lateral sieve-area pores are lined by the plasmalemma and variable amounts of callose and contain P-protein. It has been concluded that the P-protein normally is loosely arranged in the pores.

On the occurrence of nuclei in mature sieve elements

The secondary phloem of 3 species of the Taxodiaceae and 13 species of woody dicotyledons was examined for the occurrence of nuclei in mature sieve elements. Nuclei were found in all mature sieve cells of Metasequoia glyptostroboides, Sequoia sempervirens and Taxodium distichum, and in some mature sieve-tube members in 12 of the 13 species of woody dicotyledons. Except for nuclei of sieve cells undergoing cessation of function, the nuclei in mature sieve cells of M. glyptostroboides, S. sempervirens and T. distichum were normal in appearance. The occurrence and morphology of nuclei in mature sieve-tube members of the woody dicotyledons were quite variable. Only 3 species, Robinia pseudoacacia, Ulmus americana and Vitis riparia, contained some mature sieve elements with apparently normal nuclei.

SLIME SUBSTANCE AND STRANDS IN SIEVE ELEMENTS

Studies of the secondary phloem of 6 species of woody dicotyledons revealed that slime is not normally dispersed throughout the vacuole of mature sieve elements, but occurs in the form of discrete strands that traverse the cell and run from cell to cell through the sieve‐plate pores. As many as 5 fine strands, each measuring less than 0.5μ in diameter, were observed in a single pore. Less than 30% of pore area was occupied by strands. Thus, the pores are mostly open, and intervacuolar continuity exists between cells. These structural characteristics of pores offer strong support for the concept of mass flow.

Callose Substance in Sieve Elements

The secondary phloem of 6 species of woody dicotyledons was examined for the occurrence of callose on the sieve plates of active sieve elements. Fluorescence and bright-field staining methods were used to detect callose. Tissue from the 6 species was killed and fixed in each of 5 solutions. Some tissue of each species was submerged in the killing solutions as quickly as possible, the remainder within 15 min after removal from the tree. In each species, some active sieve elements of the quick-killed tissue gave negative callose reactions. All active sieve elements of the delay-killed tissue gave positive callose reactions. These and other results suggest that the active sieve elements in the secondary phloem of the species studied normally lack callose and that the extent of callose deposition in these cells depended primarily upon the rapidity with which the sieve-element protoplasts were killed after wounding of the phloem. In addition, bright-field observations of sieve plates of large numbers of sieve elements from a seasonal collection of Tilia americana secondary phloem suggest that the active sieve elements normally lack callose during the growing season and that the inactive sieve elements normally possess it (dormancy callose).

LEAF ORGANIZATION OF SOME WOODY DICOTYLEDONS FROM NEW ZEALAND

American Journal of BotanyVolume 41, Issue 3 p. 186-191 Article LEAF ORGANIZATION OF SOME WOODY DICOTYLEDONS FROM NEW ZEALAND Robert B. Wylie, Robert B. Wylie Department of Botany, State University of Iowa, Iowa City, IowaSearch for more papers by this author Robert B. Wylie, Robert B. Wylie Department of Botany, State University of Iowa, Iowa City, IowaSearch for more papers by this author First published: 01 March 1954 https://doi.org/10.1002/j.1537-2197.1954.tb14324.xCitations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume41, Issue3March 1954Pages 186-191 RelatedInformation