BIOL110s05-35 - BIOL 110: Principles of Biology Spring 2005...

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Unformatted text preview: BIOL 110: Principles of Biology Spring 2005 Lecture 35, W 4/27/05 • ONLINE Quizzes link: [Quiz #6 up until TONIGHT!!] [Quiz – (Cañada College I.D. [G#] for login and password) (Cañ – Time-limited (so study well first!); 30 minutes to complete. Time– Can view twice, submit once only. • Last chance to do Quiz #6 TODAY!!! (11:45pm) • Week 14 Lab assignments due next week, for In-Lab InDiscussion (Environmental Issues)!! (SIGN UP!!!) (SIGN • Week 15 Field Trip: Edgewood Park (@ 280 & Edgewood Road) – Grade for participation & Worksheet!!! (Replace 1 quiz!!!) • Next: 18 (bits of 19), 25, 23, 29 & 30, (31, 32). REVIEW: • Ch. 14: Origin of Life, & Microbiology – Bacteriophages & Viruses: Structures, Life cycles – Evolution of Disease • Ch. 18 (19): Plant Structure & Function – Anatomy & physiology of water & sugar transport – Reproductive physiology TODAY: • Ch. 18 (19): Plant Structure & Function – Anatomy & physiology of water & sugar transport – Reproductive physiology 1 Plant Form and Function Chapter 18 Drought versus Civilization • Periodic droughts are normal • Plants respond to drought by closing stomata, which slows growth and development • People depend on plants, and droughts can devastate a civilization 2 I. Success of the Angiosperms • The angiosperms are seed-bearing, angiosperms flowering vascular plants – Gymnosperms – no flowers/fruits, but bear seeds • Conifers, pines, furs, cycads, gingkos – Seedless: Mosses, ferns, horsetails • In terms of distribution and diversity, they are the most successful plants on Earth • The structure and function of structure this plant group help explain its success Shoots and Roots • Shoots DERMAL TISSUES – Produce food by photosynthesis VASCULAR TISSUES – Carry out reproductive functions GROUND TISSUES • Roots – Anchor the plant – Penetrate the soil and absorb water and dissolved minerals – Store food SHOOT SYSTEM ROOT SYSTEM Angiosperm 3 Meristems • Regions where cell divisions produce plant growth • Apical meristems – Lengthen stems and roots – Responsible for primary growth • Lateral meristems – Increase width/girth of stems – Responsible for secondary growth A. Vascular Tissues Xylem (up) Phloem (down) sugars • Conducts water and • Transports sugars water dissolved minerals • Main conducting cells are sieve-tube members sieve • Conducting cells are dead and hollow at maturity • Companion cells assist in the loading of sugars B. Epidermis • Covers and protects plant surfaces • Secretes a waxy, waterproof cuticle 4 II. Monocots and EuDicots • Two major plant groups • Same tissues, but arranged in different ways • Eudicots are the more diverse group (herbaceous or woody) • Differ in: 1. 2. 3. 4. 5. Cotyledon number Floral parts Leaf venation Pollen structure Arrangement of vascular bundles in stem (scattered, or ring) Adapted for Photosynthesis • Leaves are usually thin – High surface area-to-volume ratio – Promotes diffusion of carbon dioxide in, oxygen out • Leaves are arranged to capture sunlight – Are held perpendicular to rays of sun – Arranged so they don’t shade one another 5 III. Leaf Structure cuticle UPPER EPIDERMIS PALISADE MESOPHYLL xylem phloem SPONGY MESOPHYLL LOWER EPIDERMIS O2 CO2 one stoma Leaf Veins = Vascular Bundles • Xylem and phloem; often strengthened with fibers • In eudicots, veins are netlike eudicots, • In monocots, they are parallel IV. Stem Growth and Development • Cells at tip of apical meristem divide • Their descendents divide and differentiate, giving rise to specialized tissues • Lateral buds are undeveloped meristematic tissue that gives rise to stems, leaves, and flowers 6 V. Root Structure • Root cap covers tip (helmet; CO2 • Apical meristem produces the cap • Cell divisions at the apical meristem cause the root to lengthen • Farther up, cells differentiate and mature H2CO3) • ROOT HAIRS: – Extensions from the root epidermis – Greatly increase the surface area available for absorption • Root Nodules – symbiotic bacteria fix N2 • Mycorrhizae – Fungus absorbs sugars and nitrogen from the plant – Roots obtain minerals absorbed from soil by fungus Internal Structure of a Root • Outermost layer is epidermis epidermis • Root cortex is beneath the epidermis • Endodermis, then pericycle surround pericycle the vascular cylinder • In some plants, there is a central pith central tracheids and vessels in xylem sieve tubes in phloem pericycle (one or more cells thick) endodermis (one cell thick) 7 Casparian Strip in root cortex; water molecules pass through and between walls of cells Casparian strip vascular cylinder Vascular cylinder Cortex Only way that water and solutes enter VC VI. Plant Nutritional Requirements • Nearly all plants are photoautotrophs • Require carbon dioxide, water, minerals carbon • Many aspects of plant structure are responses to low concentrations of these vital resources in the environment 8 Soil • Minerals mixed with humus – Minerals come from weathering of rock – Humus is decomposing organic material • Composition of soil varies • Suitability for plant growth depends largely on proportions of soil particles • Leaching: – Removal of nutrients from soil by water that percolates through it – Most pronounced in sandy soils – Clays are best at holding onto nutrients Macronutrients & Micronutrients • Mineral elements that are required in amounts above 0.5% of the plant’s dry weight – – – – – – – – – Carbon Nitrogen Magnesium Hydrogen Potassium Phosphorus Oxygen Calcium Sulfur Elements that are required in trace amounts for normal plant growth – – – – – – – Chlorine Zinc Iron Copper Boron Molybdenum Manganese 9 VII. Root Structure and Absorption exodermis • Roots of most flowering plants have – Exodermis: just below surface – Endodermis: surrounds vascular cylinder root hair epidermis forming vascular cylinder cortex • Both layers contain a Casparian strip Casparian – Controls the flow of water and nutrients – Prevents water and solutes from passing between cells into vascular cylinder – Water and solutes must flow through cells (plasma membranes) – Flow is controlled by transport proteins • Regulation of what gets in and is transported to the rest of the plant body Casparian strip Water Use and Loss Water • Plants use a small amount of water for metabolism • Most absorbed water lost to evaporation through stomata in leaves • Evaporation of water from plant parts is transpiration transpiration 10 A. Water Transport: Xylem • Water moves through xylem • Xylem cells are tracheids or tracheids vessel members vessel • Both are dead at maturity tracheids and vessels in xylem sieve tubes in phloem pericycle (one or more cells thick) endodermis (one cell thick) B. Cohesion-Tension Theory of Water Transport 1. Transpiration creates negative tensions in xylem 2. Tensions extend downward from leaves to roots 3. Hydrogen-bonded water molecules are pulled upward through xylem as continuous columns 11 ...
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