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Botany Exam 2

Lectures 9,10,11,12,13,14

Functions of Roots Anchor plants into soil Absorption of water and minerals Store food or water
Function of Roots Absorb oxygen, epiphytes mangrove Parasitize, dodder Habitat (symbiosis), Fungi (mycorrhizaie), Bacteria (rhizobium) on legumes- root nodules- nitrogen
Importance of Roots to Humans Sources of food (carrots, sugar beets, turnips, cassava (tapioca), yams, sweet potatoes) Spices (licorice) Dyes (barberry) Drugs (ginseng) Insecticide (Rotenone from Derris sp)
The Radicle First structure (organ) to emerge (root)
Taproot System Many dicots Roots grow downwards Penetrate deeper in the soil Not easy to dislodge these plants e.g. soybean, cotton, trees
Fibrous Root System Many monocots Hold soil very well Good for soul erosion Easy to dislodge plants e.g. corn, grasses
Growth An irreversible increase in length
Differentiation Region of maturation
The Root Cap Parenchyma cells Protects apical meristem Helps, root to penetrate soul Perceive gravity, plants grow downward Positive geotropism
Region of Cell Division Apical meristem Undergoes mitosis Parent cells that produces daughter cell with identical chromosome number (diploid-diploid)
Protoderm Epidermis
Ground Meristem Cortex
Procambium Primary xylem and phloem
Region of Cell Elongation Daughter cells elongate
Region of Cell Differentiation Differentiate into tissues Root hairs Xylem and phloem
Cortex Parenchyma
Endodermis Innermost layer of cortex 1 cell thick Has suberin deposited along some of the cell wall (casparian strip) Water and minerals have to go through cell wall and cytoplasm
Casparian Strip Water and minerals cannot pass through the casparian strip
Pericycle Outer most layer of the vascualr tissue (cylinder-stele) Lateral roots arise from pericycle Vascular cambium for secondary root growth also arise from here
Movement of Water and Minerals Into Plant Osmosis + Diffusion (in case of seeds through imbibition) Root hairs (radicle in seedlings) Epidermis Cortex Endodermis Pericycle Xylem Movement upwards or lateral depending on where it is needed
Functions of Stems Support and growth Conduction of water + food to leaves/root
Hormones (stems) e.g. auxins for root production
Other specialized functions (stems) Store food Tubers (potato), bulbs (onion)
Propagation by horizontal stems Rhizomes (ginger), stolons (strawberry) Tendrils (grape)
Photosynthesis (stem) Cactus
Importance of Stems to Humans Sources of food (Idaho potato, sugarcane, onions) Wood (pine, cedar) Latex and Syrup (rubber/maple) Fiver (hemp, kenaf)
The Plumule 2nd organ (shoot) to elongate from a germinated seed Grows against gravity (negative geotropism)
Terminal Apical bud Bud at the top of the plant
Node Where leaves are attached
Axillary bud Bud at the node Terminal bud is usually larger than the axillary bud
Internode Stem region between nodes
Evergreen Don't shed their leaves
Deciduous Trees Shed their leaves during fall
Leaf Scar Left after shedding
The bundle scar Within the leaf scar, can see bundle scars (xylem + phloem)
Phyliotaxy Defined as the arrangement of leaves along the stem Helps with taxonomy
Alternate leaves Alternate on sides
Opposite Leaves On same spot on each side of stem
Leaf Primordium Immature leaves that protect the apical meristem (similar function as the root cap)
Apical Meristem Cells Form three primary meristems
Protoderm Gives rise to epidermis
Procambium Produces primary xylem and phloem
Ground Meristem Produces pith and cortex, both composed of parenchyma cells
Angiosperms Flowering plants Classified into two groups
Eudicotyledon (dicot) 2 seed cotyledon (seed leaves) Stores all food in cotyledon e.g. peanut, cotton, pea
Monocotyledon 1 seed cotyledon Cannot separate into 2 Stores most food in endosperm e.g. corn, grass
Stem Morphology Monocots and dicots can be differentiated based upon the arrangement of the vascular bundles (stele) in the stem
Dicot Stem Vascular bundles in a circle Cambium (2nd growth)
Monocot Vascular bundles are scattered No cambium
Herbaceous Plant If dicot stems have little or no secondary growth e.g. sunflower, tobacco, tomato
Secondary Growth Occurs in many angiosperms + gymnosperms Increase in thickness/girth of stem Results from vascular cambium
Cork Cambium Cork (bark) + phelloderm (parenchym)
Vascular Cambium Secondary xylem + phloem 1 years growth of xylem is called an annula ring Dendrochronology
Vascular Cambium Older darker wood is heartwood Younger, functioning xylem (near the cambium) is sapwood
Heartwood Does not conduct water Has oil, gum embedded which can make it aromatic (secondary compounds or waste) e.g. cedar
Sapwood Conducts water
Functions of Leaves Photosynthesis Gaseous exchange Transpiration
Transpiration Evaporation of water
Other specialized functions (leaves) Store food (succulents) Insect trapping (venus flytrap; pitcher plant) Reproduction and support (kalanchoe; tendrils (peas)) Spines (cactus (reduce water loss))
Importance of leaves to humans Oxygen (photosynthesis) Sources of food (cabbage, spinach) Spices (thyme, peppermint) Dyes and oils (henna; citronella) Fiber and tea (palm) Medicines (aloe; marijuana)
A Typical Leaf Blade Vein Petiole Stipule
Blade Lamina For photosynthesis
Vein Has vascular tissue
Petiole Stalk that attaches to stem
Stipule Leaf-like appendages at base of petiole (taxonomy)
Sessile Leaf If no petiole e.g. grasses, corn
Simple leaf 1 blade
Compound leaf Blade divided into leaflets
Pinnately Leaflets in pairs along the petiole Auxillary bud @ very end
Palmately Leaflets all attached at the same part of the petiole Hand (palm)
Venation Defined as arrangement of veins in a leaf
Monocot Veins Veins are parellel
Dicot Veins 1 central vein with other veins arising from it (netted) (reticulate)
Guard Cells Only epidermal cells with chloroplasts
Upper Epidermis Covered with a cuticle + waxy substances Prevents water loss (transpiration) Reflects light Some plants have a lot of hairs (trichome: reduce water loss + trap insects)
Lower Epidermis Usually have opening (stomata) If leaves are parallel to the earth, then stomata on both surfaces (monocot) If leaves are perpendicular to earth, stomata mainly on lower epidermis (dicot)
Stomata Controlled by guard cells (specialized epidermal cells) Have chloroplasts Regulate gaseous exchange Oxygen, carbon dioxide + water vapor passes through
Stomata Guard cells have a thicker inner cell wall Kidney shaped When they become turgid, stomatal opening When they become plasmolysed, stomata close
Stomata Usually open during the day, close at night
Day Photosynthesizing Increase of K+ ions into cells Decrease osmotic potential Water moves in by osmosis Increase in turgidity, become open
At night K+ ions leaves Increase in osmotic potential Water moves out Cell becomes plasmolysed, close
Mesophyll Majority of photosynthesis occurs here (parenchyma) Two layers in a typical leaf
Palisade (Mesophyll) Upper region Cells are columnar More chloroplasts Very compact
Spongy (Mesophyll) Below palisade Cells are irregular Less chloroplasts Larger intercellular airspaces
Mesophyll Monocots do not have a differentiation of mesophyll
Bulliform Cells Some may have specialized epidermal cells (bulliform) around the central vein
Why do some leaves fold Reduce water loss
Vascular Bundles (Veins) Scattered throughout mesophyll Contain xylem + phloem surrounded by thick wall parenchyma (cellenchyma) Some monocots (corn) have bundle sheath cells (C4 photosynthesis)
Leaf Abscission Normal separation of leaf from the stem
Deciduous Trees Usually more noticeable during fall when deciduous trees lose their leaves. Reusable compounds are sent to the stem e.g. sugars and amino acids Water soluble anthocyaninst carotenoids (gives leaves the color) accumulate in vacuole
Leaf Abscission A protection layer near the stem is formed (cells become embedded in suberin) A separation layer is formed
Leaf Scar Eventually only the xylem is left and will eventually break down (leaf scar + phloem)
Osmotic Potential Pressure required to prevent osmosis (influenced by solute conc.) Osmotic potential by resistance of cell wall
Turgor Pressure (pressure potential) Vacuole/cell wall exerts a pressure that stops too much water from entering the cell Turgid cell-firm cell due to water gained by osmosis
Water potential of the cell Osmotic potential + turgor pressure (pressure potential) Water moves from cell with higher water potential to cell with lower water potential
Transpiration Defined as water loss from leaves
Stomata (transpiration) Also where gaseous exchange take place Regulate transpiration (stomatal opening and closing) Stomata of most plants open during the day and close at night
Light (Transpiration) Increase light, increase transpiration
Temperature (Transpiration) As temp increased, transpiration also increases, until 30-35 C when transpiration decreases
Humidity (Transpiration) Amount of water vapor As humidity increases, transpiration decreases and vice versa
The Cohesion-Tension theory Transpiration generates tension to pull water columns through plants from roots to leaves Water columns created when water molecules adhere to tracheids and vessels of xylem and cohere to each other
Water conservation in some plants Stomata of most plants during the day and closed at night
Desert Plants Plants' stomata open only at night Conserves water, but makes carbon dioxide inaccessible during day
CAM Photosynthesis Crassulacean Acid Metabolism Carbon dioxide enters at night, converted to organic acids and stored in vacuoles
CAM Photosynthesis Organic acids converted to carbon dioxide during day for photosynthesis (stomata closed during the day) May also have stomata recessed below surface of leaf or in chambers (e.g. desert plants, pines (higher humidity))
Guttation Loss of liquid water (some plants) If cool night follows war, humid day, water droplets are produced through hydathodes (pores) at tips of veins In absence of transpiration at night, pressure in xylem elements forces water out of hydathodes
Hydathodes Pores
Transport of Organic Solutes in Solution Important function of water is translocation of food substances in solution by phloem Xylem and phloem connected
Pressure-Flow Hypothesis Organic solutes flow from source, where water enters by osmosis, to sinks, where food is utilized and water exits Organic solutes move along concentration gradients between sources and sinks
Specifics of Pressure-Flow Hypothesis Phloem loading: sugar enters by active transport (need E) into sieve tubes Water potential of sieve tubes decreases and water enters by osmosis from the xylem
Phloem Loading Turgor pressure develops and drives fluid through sieve tubes toward sinks Food actively removed at sink and water exits sieve tubes, lowering pressure in sieve tubes Process repeats
Mineral Requirements for Growth Most essential elements Essential as building blocks for compounds made by plants
Macronutrients Used by plants in greater amounts Nitrogen, potassium, phosphorus (NPK), calcium, magnesium and sulfur
Micronutrients Needed by the plants in very small amounts Iron, sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum and boron When any required element is deficient in soil, plants exhibit characteristic symptoms (soil tests)
Enzymes and Energy Transfer Oxidation-reduction reaction
Oxidation Loss of electron(s)
Reduction Gain of electron(s)
Enzymes and Energy Transfer Oxidation of one compound usually coupled with reduction of another compound with reduction of another compound is catalyzed by same enzyme or enzyme comples. Hydrogen atom is lost during oxidation and gained during reduction.
Enzymes and Energy Transfer Oxygen is usually the final acceptor of electron in the cell
Photosynthesis Production of food (sugars) Takes place in chloroplasts CH2O: building block of carbohydrate Produces most of the dry weight present in plant cells
A Chloroplast Inner and outer membrane Granum Thylakoids Stroma
A Chloroplast 75-125 chloroplast in the mesophyll in higher plants (dicots/monocots - larger organelles)
Inner and Outer membrane Protection, movement in/out
Granum (stacks of coins) Thylakoids
Thylakoids Contain chlorophyll and other pigments
Stroma Liquid matrix Enzymes, DNA, RNA, ribosomes
Important Factors in Photosynthesis CO2 Water Light Chlorophyll
CO2 Air has 78% N, 21% O, and 0.036% CO2 Diffuses through stomata into cells A steady increase in CO2 due to greenhouse gases Green plants remove carbon dioxide from atmosphere
Water Plants get most from roots If reduction in water, photosynthesis decreases
Light Visible light: Red to violet Plants absorb red-orange; violet-blue Reflect green Absorb about 80% of visible light
Light Absorbed by pigments Chlorophyll II and carotenoids which help to capture light energy
Intensity Increase intensity, increase photosynthesis Until: Photorespiration Photooxidation Stomatal closure
Photorespiration Respire and use O2; release CO2
Photooxidation Bleaching of chloroplasts- inactivation
Stomatal closure Reducing amount of CO2
Chlorophyll Mg atoms in center Similar to heme of blood hemoglobin Present in thylakoid of chloroplast
Main types of Chlorophyll a (blue-green in color) b (yellow-green in color, wider spectrum) c,d,e (certain algae) Green plants have more a than b Chlorophyll b transfers light energy to a a=dominat
Photosynthesis Divided into two steps: Light-dependent Light independent
Light-dependent (LD) Occurs in thylakoid Light energy is used to form ATP and NADPH (energy providing molecules)
Light-dependent Two photosystems are involved I and II (Z scheme- non-cyclic photophosphorylation) Consist of chlorophyll, other pigments (carotenoids) in thylakoid Reaction centers where light energy is utilized (p680 and p700)
Light - Dependent Water is split into oxygen and hydrogen and electrons
Light-Dependent Light energy (photon) from the sun hits PSII (P680) The energy boosts the electrons Chemiosmosis occurs- ATP formed (movement of ions across a selectively permeable membrane) Electrons pass along carrier molecules onto PSI (P700)
Light-Dependent Light energy (photon) from the sun hits PSI Electron passes along carrier molecules (NADPH formed) End result?
End Result? LD ATP, NADPH formed (stroma); oxygen given off
Light-Dependent (bacteria) Cyclic photophorphorylation (in bacteria) Uses only PSI Water molecule not split (no oxygen is released) No oxygen is released
End Result LD Bacteria Only ATP formed; no oxygen released
Light Independent (LI: Carbon-fixation reactions) Occurs in stroma ATP and NADPH used to reduce carbon into sugars in the Calvin Cycle
Calvin Cycle Needs RuBP-ribulose 1,5 bisphosphate And runisco (ribulose bisphosphate carboxylase/oxygenase Most abundant enzyme
First compound formed in C3 plants e.g. cotton, soybean, rice 3C sugar (3 phosphogly cerate;PGA) Reduced to glyceraldehyde 3-phosphate (G3P)- used to make glucose Happens during the day
Photorespiration Under hot, dry conditions, stomata close, no carbon dioxide enters, increases in oxygen If too much oxygen in cell, Rubisco binds to it (ribulose bisphophate Oxygenase) Formation of 2C (2-phosphoglycolate, PG) compound
Photorespiration Helps to stop photooxidation Waste ATP on NADPH, less sugars formed Allows C3 plants to survive under hot dry conditions Less production of food under these conditions
4-C Pathway Happens in C4 plants Plants that grow in dry regions e.g. Sugarcane, corn (monocots) Have a special leaf histology
The Krantz Anatomy Mesophyll cells Large bundle sheath cells LD-similar to C3 plants
Krantz Anatomy Mesophyll cells Smaller chloroplasts with well-developed grana
Krantz Anatomy Large Bundle Sheath Cells Large chloroplasts with numerous starch grains
LI and C4 Photosynthesis CO2 converted to organic acids in mesophyll cells PEP (phospheoenolpyruvat) and CO2 combine, with aid of PEP carboxylase
First compound formed instead of PGA 4C Form 4-carbon, oxaloacetic acid, instead of PGA
4C Pathway CO2 enters into Calvin cycle More efficient if climate gets hotter Less photorespiration PEP enzyme only binds to CO2, not )2 like Rubsico Rubisco more efficient if cooler temperatures
LI and CAM Plants that have crassulacean acid metabolism Succulents (+ pineapples) Orchids (epiphytes) Similar 4-C compounds to C4 photosynthesis
LI and CAM Fix CO2 in dark Live in areas of high temperature (limited water also), so stomata closes during day and only opens at night Organic acids accumulate @ night in vacuole (stomata open) Converted back to CO2 during day for use in calvin cycle (St closed)
Respiration Complete breakdown of glucose to produce E in form of ATP ATP (most versatile form of E) Occurs in mitochondrion
Anaerobic Fermentation- without oxygen- less E is produced
In plants and yeasts, what is produced? Ethanol (2C) produced (+ CO2) Used to make beer wine
In bacteria and animals, what is produced? Lactic acid (3C) Muscle fatigue Cramps
Aerobic In presence of oxygen (many organisms)
Four Steps Aerobic Respiration Glycolysis Krebs Cycle Electron Transport Chain Oxidative Phosphorylation
Glycolysis Occurs in cytoplasm Glucose is broken down into 2 molecules of pyruvate No oxygen is used Formation of ATP and NADH (another source of energy)
What is net formation? Glycolysis 2 molecules each of NADH and ATP 1 NADH make 2 molecules of ATP NADH has to be transported across the mictochondrial membrane Uses 1 ATP to transport NADH
Glycolysis If O2 available, anaerobic respiration occurs after glycolysis
Krebs Cycle Pyruvate enters in to mitochondrion Oxygen is necessary
Net formation? Krebs Cycle (from x2 pyruvates) 1 ATP 4 NADH 1 FADH2- high E molecules
Electron Transport Chain Electrons present in NADH and FADH2 pass along an electron gradient (in mitochondrion) Acceptance by several other molecules NADH and FADH2 oxidized to NAD+, FAD+, H+,e-
Oxidative Phosphorylation Energy given off by electrons down chain produces ATP (ADP to ATP) [in mitochondrion] Electrons then accepted by oxygen and combine wit H+ ions to produce water 2H+ + 1/2 O2 ---> H2O NADH forms 3 ATP FADH2 forms 2 ATP
What is the overall net from 1 glucose molecule 6 molecules of H20 and CO2
Factors affecting respiration Temperature Water Oxygen
Temperature (respiration) Increase temperature, increases respiration Too much increase in temp Kill plants Due to loss of enzyme action
Water (respiration) Decrease water, decreases respiration
Oxygen (respiration) Decrease oxygen, decrease respiration Improve seed viability (store for a longer time)
Created by: rrawls914



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