BIO 1144 Sec 03 Week of Feb 8 Notes
BIO 1144 Sec 03 Week of Feb 8 Notes BIO 1144
Popular in Biology II Thomas Holder
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This 8 page Class Notes was uploaded by Jaren Davis on Friday February 12, 2016. The Class Notes belongs to BIO 1144 at Mississippi State University taught by Thomas Holder in Spring 2016. Since its upload, it has received 21 views. For similar materials see Biology II Thomas Holder in Biology at Mississippi State University.
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Date Created: 02/12/16
• Gibberellins (Gibberellic Acids) ◦ Found in plants ◦ Growth promoting hormones ◦ Produced/found throughout the plant ‣ Highly concentrated in seeds ◦ Effects ‣ Promote stem elongation by cell elongation ‣ Promote cell division ‣ Promote the breakdown of food reserves in germinating seeds Food breakdown: • Intake of h2O causing swelling ◦ Cracking of seed coats • Embryo secretes Gibberellins • Gibbs transported to Aleurone • Aleurone layer secretes enzyme ◦ (Alpha - amylase) > breaks down starch • Starch ---> Glucose ---> yields ◦ ATP (biological energy) for growth • Embryo directs process! ◦ Cues from H2O • Advantage of seed plants! • Abscisic Acid ◦ Growth inhibitor ◦ Found in the mature leaves, dormant buds, and seeds ◦ Effects: ‣ Inhibits cell elongation ‣ Inhibits alpha-amylase secretion by the aleurone layer ‣ Promotes the production of storage compounds in seeds to prevent early germination ‣ Promotes leaf senescence (leaves change color) • Trying to promote growth • Ethylene ◦ Growth inhibitor ◦ Might not be a hormone ◦ A gas released from the plant ◦ Effects: ‣ Interacts with the three growth promoting hormones to regulate cell size and shape ‣ Promotes the abscission of leaves, fruits, and flowers ‣ Promotes fruit ripening Growth From Seed Requires • Breaking of dormancy ◦ Combination of internal and external factors ◦ Internal ‣ Hormones ‣ Stored food ‣ Absorption H2O ‣ Embryo swelling ◦ External ‣ Sunlight ‣ Temperature ‣ Increase in day length ‣ Soil moisture ◦ Seed contains: seed coat(s), embryo, stored food ◦ As seed coats crack: ‣ Radicle: (1st root) ---> grows down ‣ Shoot (stem and leaves) ---> grows up ‣ Cotyledons - emerge • "Embryonic leaves" • 1 cotyledon (monocot) • 2 cotyledons (dicots) • Seedling Plant - ◦ Result of mitosis/cytokinesis (cell repro.) ◦ Increase in cell size • Internal development - ◦ Plant cells ---> plant tissues ---> plant organs ‣ Tissue - an aggregation of functionally similar cells ‣ Organs - root, stem, leaf ‣ Organism = plant • Plant nutrition ◦ More than 60 different elements in plants ◦ Essential elements (nutrients) - 16 ‣ C, H, O ---> from CO2 (from the atmosphere) and H2O (roots) ‣ 13 soil nutrients (minerals) • Absorbed dissolved in H2O through roots; follow pathway with H2O • Macronutrients (6) ◦ Called macro because they require more than 1 gram in dry weight ◦ Nitrogen (N) ‣ Component of coenzymes, proteins, nucleic acids, and chlorophyll ◦ Potassium (K) ‣ Functions as enzyme activator; involved in the opening and closing of leaf stomata ‣ Ionic balance of cells ◦ Phosphorous (P) ‣ Component of nucleic acids ‣ Component of biological energy molecules ‣ Component of coenzymes ‣ Component of phospholipids ◦ Calcium (Ca) ‣ Component of cell walls ‣ Regulator of membrane and enzyme activities ‣ Involved with membrane permeability ◦ Sulfur (S) ‣ Component of some proteins and some coenzymes ◦ Magnesium (Mg) ‣ Enzyme activator ‣ Component of chlorophyll • Micronutrients (7) "trace minerals/elements" ◦ Less than 1 gram ◦ Molybdenum (Mb) ‣ Necessary for nitrogen fixation and absorption ◦ Copper (Cu) ‣ Activator or component of many enzymes ◦ Zinc (Zn) ‣ Activator or component of many enzymes ◦ Manganese (Mn) ‣ Enzyme activator ‣ Part of the chloroplast membrane ‣ Involved with oxygen release in the chloroplast ◦ Chlorine (Cl) ‣ Involved with ion balance and oxygen production during photosynthesis ◦ Boron (B) ‣ Associated with membrane structure ‣ Necessary for nucleic acid synthesis ◦ Iron (Fe) ‣ Necessary for chlorophyll production Transport Moment of H2O and Solutes in Plants • H2O (soil nutrients) ◦ Xylem • Food (carbohydrates, hormones) ◦ Phloem • Importance of H2O ◦ Photosynthesis ◦ Support for plant organs ◦ Conduction ◦ Cell elongation ◦ Nearly all chemical reactions involve water ‣ Some require water, some produce water ◦ Average plant cell ---> 90% water ◦ Primary solvent for most substances ‣ Solution • Mixture of two or more compounds ‣ Solvent • Compound in a solution, usually in the greatest quantity, and usually a liquid ‣ Solute • The chemical in solution of lesser quality that is usually dissolved • Properties of H2O ◦ Water is a polar molecule ◦ Neutral charge ◦ Hydrogen bonding - each H2O is H-bonded to 4 other molecules ‣ Water is powerful because of hydrogen bond ‣ Water forms a "tight net" ‣ Water is very cohesive • Water molecules stick together tightly ‣ Water is adhesive - cellulose • Stick to other polar compounds • Sticks to cellulose ◦ Water is a temperature stabilizer ◦ Water is a good transport medium ◦ Water is the best biological solvent ◦ Found in all 3 physical forms at earth's temperature range Principles of H2O and molecules Movement • Physical processes - no energy expended • Bulk Flow ◦ The movement of molecules in response to pressure or gravity from high to low concentration • Diffusion ◦ The movement of molecules along a concentration gradient from high to low concentration • Osmosis ◦ The diffusion of water across a selectively permeable membrane ‣ Restricts other things from moving ‣ Can't stop water • With osmosis, water passes freely through membrane, solutes do not. • Water movement (and soil minerals) through plant - ◦ Transpiration - "cost" land plants have to pay ‣ Example: corn plant - requires 55 gallons of water • 2% - normal maintenance ◦ Photosynthesis, cell elongation • 98% - transpired ◦ Sweating ‣ Definition: The loss of water exiting through the stomata of the leaf • Water is in vapor form • Comes back in some form • Loss is required for the movement of water Function: regulate stoma, control water loss Closed ---> low in water Open ---> guard cells full of water (turgid) Pair of Guard Cells with Stoma - • Open ---> water out; O2 out; CO2 in • Closed ---> hold water; no CO2 in, no O2 out Mechanism: • Daytime/sunlight - CO2 low in leaf • Guard cells "pump in" K (ATP expend.) ◦ Changes solute (goes up)/H2O (goes down) concentration • Water from xylem moves into mesophyll by osmosis into guard cells ---> "turgid" • Guard cells swell and stoma opens • "Pump out" K, water moves out, guard cells shrink and close the stoma Causes of Water Loss - ultimately, it is sunlight, energy; "Heating" • Sun heats up leaf, causing the evaporation of H2O from mesophyll cells • Causes lower water concentration in mesophyll • Causing a "pull" of water molecules by the process of osmosis from leaf xylem • "pull" from stem xylem which is connected to the root xylem • Pulling in water (and nutrients) from soil • "Transpiration Stream" ◦ Unidirectional flow ◦ Flows up, not back down ◦ Transpiration Stream Stem xylem Leaf xylem Root xylem Mesophyll Root cortex Evaporates Vapor Root epi. Atmosphere Soil h2o (Nutrients) C-A-T Mechanism • Once the stomata opens • "Pull" of H2O molecules one at a time ◦ Cohesion - H2O molecules together ◦ Adhesion - adheres to cellulose in walls ‣ Water doesn't slid back down or flowing ◦ Tension - "pull" due to water loss by evaporation from mesophyll • No energy is expended - "pull" is all the way down • Energy to cause evaporation - sunlight, not the plant Translocation - movement of solutes No energy expended • Similarities between translocation and transpiration ◦ Physical properties of water • Differences ◦ Translocation ‣ Food / solutes ‣ Bidirectional ‣ Phloem ‣ Must expend ATP energy by plant ◦ Transpiration ‣ Water / minerals ‣ Unidirectional ‣ Xylem ‣ Sunlight energy (no expenditure by plant) Food - dissolved in water; moved in the form of sucrose • Source -------------> sink Highly modified, short • Source term shoot system ◦ Site of excess carbohydrate • Sink ◦ The storage site or the site where sugar is quickly needed Pressure flow Hypothesis • Involves changes in pressure in cells and the flow is bulk flow and dissolved in water • Phloem tissues - sieve tube members - companion cells - load and unload STMs (ATP expenditure) At Source: • Companion Cells "pump" sucrose into STMs (ATP expenditure) • As source concentration increases in STMs, water potential decreases within STM (pressure) (H2O concentration) • Adjust xylem has higher water potential than STMs; H2O moves into STMs by osmosis • Bulk flow of sucrose (higher pressure to lower pressure) At Sink: • Companion cells unload sucrose (ATP expenditure) • Sucrose converted to starch for storage in root cortex • Without sucrose, water potential changes, higher water potential in STM (pressure) • Water moves from STM to adjacent xylem by osmosis ATP spent only by com. cells at source (loading) and sink (unloading) Bulk flow (pressure/ potential diffs.) Osmosis (water potential diffs.) Concentration Flower and Sexual Cycle • Angiosperms only! • 300,000 species • Come in all sizes, shapes, colors, and aromas • Essential processes of sexual reproduction occur within flower ◦ Meiosis/cytokinesis : reduces chromosome number ◦ Syngamy (fertilization) ‣ Restores chromosome number (1N + 1N = 2N) • "Ideal Flower" ◦ 4 sets of highly modified leaves in whorls at tip of modified stem
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