Plant Structure and Function PDF

Chapter 28 Plant Structure and Growth https://parade.com/23643/linzlowe/what-the-heck-is-romanesco-and-how-do- you-cook-it/ Romanesco Angiosperms (flowering plants) Two major clades:  Monocots – one seed leaf (cotyledons)...

Chapter 28 Plant Structure and Growth https://parade.com/23643/linzlowe/what-the-heck-is-romanesco-and-how-do- you-cook-it/ Romanesco Angiosperms (flowering plants) Two major clades:  Monocots – one seed leaf (cotyledons)  Eudicots – two seed leaves Fig. 28.2 Concept 28.1: Plants have a hierarchical organization consisting of organs, tissues, and cells Plants organs  organ several types of tissues that do a job  tissue one or more cell types that do a job © 2014 Pearson Education, Inc. The Three Basic Plant Organs: Roots, Stems, and Leaves Plant body: takes water and minerals from below ground and takes CO2 and light from above ground © 2014 Pearson Education, Inc.  root system plant’s roots. Underground; sugar from leaves ‘feeds’ roots.  shoot system stems, leaves, and flowers; water and minerals absorbed by the root system is transported to the shoots. Roots  Anchors plant, absorbs minerals and water, and stores carbohydrates.  root systems  Taproot Eudicots; main vertical root and lateral roots branching off the taproot © 2014 Pearson Education, Inc.  root systems  Fibrous Monocots; mat of thin roots all about the same size; adventitious or arise from stems and leaves © 2014 Pearson Education, Inc. Stems have leaves and buds; elongate and orient shoots to maximize photosynthesis  Nodes where leaves attach  Internodes segments between nodes Fig 28.3  apical bud compact series of nodes and internodes near the shoot tip  axillary bud in upper angle formed by the leaf and the stem; generally dormant but can form a lateral branch, thorn, or flower  modified stems Horizontal shoot that grows just below surface Horizontal shoots along the surface with little plantlets at each node. Enlarged ends of rhizomes Fig 28..6 to store food; eyes of potatoes are axillary buds! Leaves  main photosynthetic organ; allow gas exchange, dissipation of heat, and defense  flattened blade; stalk = petiole, joins leaf to the stem veins vascular tissue of leaves  Monocots parallel veins  Eudicots branching veins  modified leaves Fig 28.7 Dermal, Vascular, and Ground Tissue Systems  vascular tissue system transport of materials; mechanical support Fig 28.8 Dermal, Vascular, and Ground Tissue Systems vascular tissues  xylem conducts water and dissolved minerals from roots into the shoots  phloem transports organic nutrients from where they are made to where needed  Stele vascular tissue of a root or stem  Angiosperms = solid central region  stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem © 2014 Pearson Education, Inc. dermal tissue system outer protective covering  nonwoody plants epidermis outer layer of cells  cuticle waxy coating; prevents water loss  woody plants periderm replaces epidermis in older regions of stems and roots; protective layer Ground tissue system tissues that are neither dermal nor vascular  ground tissue is internal to the vascular tissue = pith  ground tissue is external to the vascular tissue = cortex.  includes cells specialized for photosynthesis, short- distance transport, storage, or support Common Types of Plant Cells  Parenchyma  Collenchyma  Sclerenchyma  Water-conducting cells of the xylem  Sugar-conducting cells of the phloem Parenchyma cells  Thin, flexible primary walls  Lack secondary walls  large central vacuole  Perform the most metabolic functions  Photosynthesis  can divide and differentiate  Collenchyma cells  grouped in strands  thicker and uneven cell walls  Lack secondary walls  flexible support http://emp.byui.edu/wellerg/Cell%20Types%20and%20Tissues%20Lab/ Instructions/Cell%20Types%20and%20Tissues%20Lab%20Instructions Sclerenchyma cells  Rigid; secondary walls contain lignin, a strengthening polymer  dead at functional maturity Sclerenchyma cells Two types  Sclereids short and irregular; thick  Fibers long, slender; grouped in strands  Materials used in textiles (fabrics, paper, etc.)  Water-conducting cells of the xylem  dead at maturity  Two types  Tracheids long, thin, tapered ends; move water through pits  Vessel elements align end to end; form long micropipes called vessels Sugar-conducting cells of the phloem  alive at functional maturity  sugars transported in sieve tubes  chains = sieve-tube elements (lack organelles; has a companion cell whose nucleus and ribosomes serve both cells)  Sieve plates porous end walls; allow fluid to flow between cells. Concept 28.2: Meristems generate new cells for growth and control the developmental phases and life spans of plants  indeterminate growth Can grow throughout lifetime; enabled by meristems (perpetually undifferentiated tissues)  determinate growth plant organs cease to grow at a certain size Two main types of meristems  Apical meristems  Lateral meristems  Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots  elongate shoots and roots, a process called primary growth  Lateral meristems add thickness to woody plants, a process called secondary growth Two lateral meristems:  vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem  cork cambium replaces the epidermis with periderm, which is thicker and tougher  woody plants primary growth extends the shoots and secondary growth increases the diameter of previously formed parts Flowering plants can be classified by life cycle  Annuals complete their life cycle in a year or less  Biennials require two growing seasons  Perennials live for many years Concept 29.6: The rate of transpiration is regulated by stomata  Leaves broad surface areas; high surface-to-volume ratios; increase photosynthesis and water loss through stomata  Guard cells balance water conservation with gas exchange for photosynthesis. About 95% of the water a plant loses escapes through stomata  stoma surrounded by pair of guard cells; control the diameter of the stoma by changing shape. Mechanisms of Stomatal Opening and Closing  Changes in turgor pressure open and close stomata  turgid guard cells bow outward; pore opens  flaccid guard cells less bowed; pore closes  Changes in turgor pressure result from uptake and loss of potassium ions (K) by the guard cells Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed H2O H2O H2O H2O K+ H2O H2O H2O H2O H2O H2O (b) Role of potassium ions (K+) in stomatal opening and closing Adaptations That Reduce Evaporative Water Loss  Xerophytes plants adapted to arid climates  Some desert plants complete their life cycle during the rainy season  Others have leaf modifications that reduce the rate of transpiration  Some plants use a specialized form of photosynthesis called crassulacean acid metabolism (CAM) where stomatal gas exchange occurs at night Concept 29.7: Sugars are transported from sources to sinks via the phloem Translocation transports sugars through phloem  Phloem sap aqueous solution high in sucrose; travels from sugar source to a sugar sink.  sugar source organ that is a net producer of sugar, e.g. mature leaves.  sugar sink organ that is a net consumer or stores sugar, e.g. tuber or bulb Green dots are sugar. Loaded into sieve tube at source. Reduces water potential inside the sieve-tube elements causing the tube to take up water by osmosis. Water uptake generates positive pressure forcing sap to flow along a tube. The pressure is relieved by the unloading of sugar and the loss of water at the sink. In leaf-to-root translocation, xylem recycles water from sink to source.