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01 2 342 3567897978 767899798 7 777 !"#$%# !&' #$ ()(* +,-./0,-12*1-3,-.12*4.5,15, *)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)*)* 6789:;<=>?()@* SeedlessVascularPlantsSeedlessVascularPlants Bởi: OpenStaxCollege The vascular plants, or tracheophytes, are the dominant and most conspicuous group of land plants More than 260,000 species of tracheophytes represent more than 90 percent of Earth’s vegetation Several evolutionary innovations explain their success and their ability to spread to all habitats Bryophytes may have been successful at the transition from an aquatic habitat to land, but they are still dependent on water for reproduction, and absorb moisture and nutrients through the gametophyte surface The lack of roots for absorbing water and minerals from the soil, as well as a lack of reinforced conducting cells, limits bryophytes to small sizes Although they may survive in reasonably dry conditions, they cannot reproduce and expand their habitat range in the absence of water Vascular plants, on the other hand, can achieve enormous heights, thus competing successfully for light Photosynthetic organs become leaves, and pipe-like cells or vascular tissues transport water, minerals, and fixed carbon throughout the organism In seedlessvascular plants, the diploid sporophyte is the dominant phase of the lifecycle The gametophyte is now an inconspicuous, but still independent, organism Throughout plant evolution, there is an evident reversal of roles in the dominant phase of the lifecycle Seedlessvascularplants still depend on water during fertilization, as the sperm must swim on a layer of moisture to reach the egg This step in reproduction explains why ferns and their relatives are more abundant in damp environments Vascular Tissue: Xylem and Phloem The first fossils that show the presence of vascular tissue date to the Silurian period, about 430 million years ago The simplest arrangement of conductive cells shows a pattern of xylem at the center surrounded by phloem Xylem is the tissue responsible for the storage and long-distance transport of water and nutrients, as well as the transfer of water-soluble growth factors from the organs of synthesis to the target organs The tissue consists of conducting cells, known as tracheids, and supportive filler tissue, called parenchyma Xylem conductive cells incorporate the compound lignin into their walls, and are thus described as lignified Lignin itself is a complex polymer that is impermeable to water and confers mechanical strength to vascular tissue With their rigid cell walls, the xylem cells provide support to the plant and allow it to achieve 1/14 SeedlessVascularPlants impressive heights Tall plants have a selective advantage by being able to reach unfiltered sunlight and disperse their spores or seeds further away, thus expanding their range By growing higher than other plants, tall trees cast their shadow on shorter plants and limit competition for water and precious nutrients in the soil Phloem is the second type of vascular tissue; it transports sugars, proteins, and other solutes throughout the plant Phloem cells are divided into sieve elements (conducting cells) and cells that support the sieve elements Together, xylem and phloem tissues form the vascular system of plants Roots: Support for the Plant Roots are not well preserved in the fossil record Nevertheless, it seems that roots appeared later in evolution than vascular tissue The development of an extensive network of roots represented a significant new feature of vascularplants Thin rhizoids attached bryophytes to the substrate, but these rather flimsy filaments did not provide a strong anchor for the plant; neither did they absorb substantial amounts of water and nutrients In contrast, roots, with their prominent vascular tissue system, transfer water and minerals from the soil to the rest of the plant The extensive network of roots that penetrates deep into the soil to reach sources of water also stabilizes trees by acting as a ballast or anchor The majority of roots establish a symbiotic relationship with fungi, forming mycorrhizae, which benefit the plant by greatly increasing the surface area for absorption of water and soil minerals and nutrients Leaves, Sporophylls, and Strobili A third innovation marks the seedlessvascularplants Accompanying the prominence of the sporophyte and the development of vascular tissue, the appearance of true leaves improved their photosynthetic efficiency Leaves capture more sunlight with their increased surface area by employing more chloroplasts to trap light energy and convert it to chemical energy, which is then used to fix atmospheric carbon dioxide into carbohydrates The carbohydrates are exported to the rest of the plant by the conductive cells of phloem tissue The existence of two types of morphology suggests that leaves evolved independently in several groups of plants The first type of leaf is the microphyll, or “little leaf,” which can be dated to 350 million years ago in the late Silurian A microphyll is small and has a simple vascular system A single unbranched vein—a bundle ...Ann. For. Sci. 64 (2007) 765–772 Available online at: c INRA, EDP Sciences, 2007 www.afs-journal.org DOI: 10.1051/forest:2007056 Original article Arbuscular mycorrhizal colonization of vascularplants from the Yungas forests, Argentina Alejandra B a * ,MartaC b ,FrancoC a a Instituto Multidisciplinario de Biología Vegetal, CONICET-UNC. C.C. 495. 5000 Córdoba, República Argentina b Instituto Spegazzini, Facultad de Ciencias Naturales y Museo, Avenida 53, N ◦ 477, 1900 La Plata, República Argentina (Received 21 November 2006; accepted 7 June 2007) Abstract – In Argentina, the Yungas forests are among the ecosystems most affected by human activity, with loss of biodiversity. To assess the mycor- rhizal status in these ecosystems, the roots of 41 native plant species belonging to 25 families were collected throughout the year from two sites of the Yungas forests. Roots were washed and stained to study the presence of arbuscular mycorrhizas (AM). Morphological types of arbuscular mycorrhizas (Arum and Paris-type) and colonization patterns were identified and photographed. All plants presented AM colonization. The AM colonization patterns varied from single intracellular aseptate hyphae, coils, appresoria, to vesicles and/or arbuscules. Among the species studied, the Pari s -type colonization showed to be dominant. Results confirmed that AM hosts are predominant in the Yungas of South American forests. Yungas / arbuscular mycorrhizal / Arum-type / Paris-type / Alnus fo rests Résumé – Colonisation par les mycorhizes arbusculaires dans des plantes vasculaires des forêts des Yungas, Argentine. En Argentine, les Yungas constituent un des écosystèmes les plus atteints par l’activité de l’homme, avec la perte de biodiversité qui en découle. Pour évaluer le statut mycorhizien de ces écosystèmes, les racines de 41 plantes autochtones appartenant à 25 familles ont été collectées au cours de l’année dans deux sites des forêts des Yungas. Les racines ont été lavées et teintes afin de déterminer la présence des mycorhizes arbusculaires (MA). Les types morphologiques de MA (type Arum et Par i s) et les patrons de colonisation ont été identifiés et photographiés. Toutes les plantes ont présenté une colonisation MA. Les structures fongiques intraracinaires comprenaient des hyphes intracellulaires sans cloison, des boucles, des appressoria, des vésicules et/ou des arbuscules. Le type de colonisation Pari s est apparu comme dominant parmi les espèces étudiées. Les résultats confirment que les hôtes avec MA prédominent dans les forêts sudaméricaines des Yungas. Yungas / mycorhizes arbusculaires / type Arum / type Paris / bois d’Alnus 1. INTRODUCTION The Yungas, or Tucuman-Bolivian forests [20, 49], which belongs to the humid subtropical South American ecosystems, have a great regional relevance due to their high diversity [15]. However, the Yungas are among the ecosystems most affected by human activity, with the consequent loss of biodiversity. In order to conserve biodiversity, not only is it necessary to iden- tify areas with high diversity of species, but it is also necessary to preserve different areas to protect genetic and environmen- tal variation [15]. The Yungas are located between 300 and 3000 masl [20]. Three main environmental units can be recognized: The Pre- montane Forest (300–600 m asl), at present almost completely transformed into an intensive agricultural area; the Montane Forest (600–1500 m asl), where forestry and cattle raising are practiced, and the Montane Cloud Forest (1500–3000 m asl), which is being replaced by anthropic grasslands for cattle rais- inginsomesectors. The latter environmental unit, the montane cloud for- est, has been divided into three plant communities, namely, “Podocarpus parlatorei Pilg. (Podocarpaceae) forests”, “Al- * Corresponding author: abecerra@efn.uncor.edu nus acuminata Kunth (Betulaceae) forests”, and “Sambucus peruviana Kunth (Caprifoliaceae) and Polylepis australis Bitt. Ch 36 Warm-Up Describe the process of how H2O gets into the plant and up to the leaves Compare and contrast apoplastic flow to symplastic flow Explain the mass flow of materials in the phloem (source to sink) Ch 36 Warm-Up What is transpiration? What are mycorrhizae? What is the function of the Casparian strip? Chapter 36 Resource Acquisition and Transport in VascularPlants What you need to know: The role of passive transport, active transport, and cotransport in plant transport The role of diffusion, active transport, and bulk flow in the movement of water and nutrients in plants How the transpiration cohesion-tension mechanism explain water movement in plants How pressure flow explains translocation What does a plant need? Review: Selectively permeable membrane: osmosis, transport proteins, selective channels Proton pump: active transport; uses E to pump H+ out of cell proton gradient Cotransport: couple H+ diffusion with sucrose transport Aquaporin: transport protein which controls H2O uptake/loss Solute transport across plant cell plasma membranes Osmosis **Water potential (ψ): H2O moves from high ψ low ψ potential, solute conc & pressure ◦ Water potential equation: ψ = ψS + ψP ◦ Solute potential (ψS) – osmotic potential ◦ Pressure potential (ψP) – physical pressure on solution ◦ Pure water: ψS = Mpa ◦ Ψ is always negative! ◦ Turgor pressure = force on cell wall Bulk flow: flow move H2O in plant from regions of high low pressure ** Review AP Bio Investigation Flaccid: limp (wilting) Plasmolyze: shrink, pull away from cell wall (kills most plant cells) due to H2O loss Turgid: firm (healthy plant) Turgid Plant Cell Plasmolysis A watered impatiens plant regains its turgor Vascular Tissues: conduct molecules Xylem Phloem Nonliving functional Living functional Xylem sap = H2O & minerals Phloem sap = sucrose, minerals, amino acids, hormones Source to sink (sugar made) to (sugar consumed/stored) Transport of H2O and minerals into xylem: Root epidermis cortex [Casparian Strip] vascular cylinder xylem tissue shoot system At Root Epidermis Root hairs: increase surface area of absorption at root tips Mycorrhizae: symbiotic relationship between fungus + roots ◦ Increase H2O/mineral absorption The white mycelium of the fungus ensheathes these roots of a pine tree Transport pathways across Cortex: Apoplast = materials travel between cells Symplast = materials cross cell membrane, move through cytosol & plasmodesmata Entry into Vascular Cylinder: Endodermis (inner layer of cortex) sealed by Casparian strip (waxy material) ◦ Blocks passage of H2O and minerals ◦ All materials absorbed from roots enter xylem through selectively permeable membrane ◦ Symplast entry only! How does material move vertically (against gravity)? Transpiration: Transpiration loss of H2O via evaporation from leaves into air Root pressure (least important) Diffusion into root pushes sap up Cohesion-tension hypothesis ◦ ◦ Transpiration provides pull Cohesion of H2O transmits pull from rootsshoots Guttation: exudation of water droplets seen in morning (not dew), caused by root pressure Stomata regulate rate of transpiration Stomata – pores in epidermis of leaves/stems, allow gas exchange and transpiration Guard cells – open/close stoma by changing shape ◦ Take up K+ lower ψ take up H2O pore opens ◦ Lose K+ lose H2O cells less bowed pore closes Cells stimulated open by: light, loss of CO2 in leaf, circadian rhythms Stomata closure: closure drought, high temperature, wind BIOFLIX: WATER TRANSPORT IN PLANTS Sugar Transport Translocation: transport of sugars into phloem by pressure flow Source Sink ◦ Source = produce sugar (photosynthesis) ◦ Sink = consume/store sugar (fruit, roots) Via sieve-tube elements Active transport of sucrose Bulk flow in a sieve tube Symplast is dynamic Plasmodesmata allows movement of RNA & proteins between cells Phloem can carry rapid, long-distance Chuyển đổi tài liệu PDF sang Word 01:07' 22/11/2005 (GMT+7) Word đã trở thành "vua" của các bộ soạn thảo văn bản. Hầu hết các văn bản đều được định dạng và in bằng Word. Tuy nhiên, bạn có một số văn bản bằng PDF (Portable Document Format), bạn muốn chỉnh sửa các tài liệu này trước khi in ấn. Acrobat Reader không có khả năng chỉnh sửa văn bản, còn Acrobat thì giá cả hơi "mắc" mà lại đòi hỏi tài nguyên khá lớn. Vậy, có phần mềm nào có khả năng chuyển đổi định dạng từ PDF sang Word mà vẫn giữ nguyên định dạng, giá cả cũng chấp nhận được và lại tiêu tốn ít tài nguyên hệ thống ? Thực ra, để giữ nguyên các định dạng tài liệu sau khi chuyển đổi là rất phức tạp và khó khăn. Đến ngay như phần mềm Acrobat, khi chuyển đổi tập tin PDF sang Word cũng không được hoàn hảo. Tuy nhiên, nếu bạn đã từng sử dụng qua phần mềm SolidPDFConverter của hãng Solid, phần mềm này thật tuyệt vời ! Các tài liệu phức tạp gồm các nội dung văn bản, hình ảnh, bảng tính . vẫn giữ nguyên định dạng sau khi chuyển đổi sang Word. 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Exact sử dụng các TextBox của Word để đảm bảo chắc chắn văn bản và đồ họa vẫn giống y nguyên bản PDF gốc.Chế độ Exact không nên sử dụng nếu bạn cần chỉnh sửa rất nhiều nội dung từ SeedlessPlantsSeedlessPlants Bởi: OpenStaxCollege An incredible variety of seedlessplants populates the terrestrial landscape Mosses grow on tree trunks, and horsetails ([link]) display their jointed stems and spindly leaves on the forest floor Yet, seedlessplants represent only a small fraction of the plants in our environment Three hundred million years ago, seedlessplants dominated the landscape and grew in the enormous swampy forests of the Carboniferous period Their decomposing bodies created large deposits of coal that we mine today Seedlessplants like these horsetails (Equisetum sp.) thrive in damp, shaded environments under the tree canopy where dryness is a rare occurrence (credit: Jerry Kirkhart) Bryophytes Bryophytes, an informal grouping of the nonvascular plants, are the ... most readily recognizable seedless vascular plants They are considered the most advanced seedless vascular plants and display characteristics commonly observed in seed plants More than 20,000 species... Carboniferous its name In seedless vascular plants, the sporophyte became the dominant phase of the lifecycle Water is still required for fertilization of seedless vascular plants, and most favor... cones Ferns and Other Seedless Vascular Plants By the late Devonian period, plants had evolved vascular tissue, well-defined leaves, and root systems With these advantages, plants increased in