Plant Physiology Chapters Angiosperms Flowering Plants AP Biology

Plant Physiology Chapters Angiosperms – Flowering Plants AP Biology

Chapter 1 Plant Form and Function

Monocots vs. Dicots n n Grass, wheat, corn , rice, sugar cane Fibrous roots Parallel veins Flowers in 3’s n n n Most others Tap Roots Net-like veins Flowers in 4’s and 5’s Can become woody

Plant Organs and Tissues n Organs: roots, stem, leaves – all organs are made out of the same three tissues Tissues n n Dermal Tissue – epidermis – protective Vascular Tissue – veins – carry food and water n n n Xylem – carries water and minerals – made of tracheids and vessel elements Phloem – carries sugar – made of sieve tubes and companion cells Ground Tissue – everything else – used for support, photosynthesis, storage n n Pith-ground tissue inside vascular tissue Cortex-ground tissue outside of vascular tissue

Outside layer = epidermis – dermal tissue for protection Cortex = ground tissue – storage of food, uptake of minerals Steele = xylem and phloem – vascular tissue Root Hairs – increase surface area for increased water absorption

Root vs. Shoot System n n n Root system (roots) Takes water and minerals from the soil (absorbs from the tips n n of the roots and root hairs increase surface area from absorption) n Anatomy: n n n Tap roots (dicots) – a large vertical root with smaller lateral roots (store food) Fibrous roots (monocots) – matlike roots that spread Shoot system (stem, leaves, flowers) Takes CO 2 from the air, make sugar, plant reproduction Transports sugar to the rest of the plant Anatomy n Stems: n n Nodes – where leaves attach Buds – create more shoots n n Terminal buds – end of stem – cause apical dominance – inhibits side growth Axillary buds – side bud. S Leaves: Petiole – attaches leaf to the node (not in monocots – leaf ensheathed in stem) Flowers – modified leaves with stem specialized for reproduction

Dicot Roots: Epidermis – dermal Cortex – ground Vascular vascular Stems Vascular Bundle Cortex Epidermis Vascular Bundle

←Dicot – C 3 Plant Monocot – C 4 Plant→

Plant Cell Types n Parenchyma – “normal plant cells” – have large vacuoles, no secondary cell wall, usually not mitotic, but can be stimulated to divide in injury Examples: Most of the cells that make up ground tissue n n n Photosynthetic cells in leaf mesophyll Cells that store starch in stems and roots Fruit cells – store sugar Sieve tube cells that make up phloem Collenchyma – cells are elongated, thicker primary wall but no secondary cell wall, provides for growth and support Examples: n n n Cells that support young stems and petioles Some ground tissue Sclerenchyma – rigid secondary cells walls (can’t elongate), may be dead and used for plant support Examples: n n n The shells of nuts and outer coat of seeds Fiber cells – used to make plant fibers that are used to make rope Tracheids and Vessel Elements (make up xylem) – dead water conducting cells used for support (cells disintegrate leaving empty cell with a double cell wall – water moves from cells to cell through pits or end to end perforations

sclerenchyma

Plant Growth n n n Meristems embryonic tissue (stem cells – undifferentiated) – can divide and become any kind of plant cell Primary Meristems(apical) – make plant grow longer – in root tips and at buds or new shoots Secondary Meristems(lateral) – make plant grow wider – in stem – adding more xylem which becomes wood

Lateral Growth n n Lateral Meristems also called vascular cambium – forms between xylem and phloem so there is a continuous cylinder around xylem and interior ground tissue It forms 2 ndary xylem on the inside and 2 ndary phloem on the outside

Lateral Growth n n Xylem (wood) Over the years, vascular cambium makes many layers of 2 ndary xylem on the inside (made of tracheids and vessel elements with very strong cell walls) – This is wood! Only the most exterior xylem works to carry water. Interior xylem dies and harden more Phloem (part of bark) Formed outside the vascular cambium – only newest xylem closest to interior is alive and transports food – rest dies and sloughs off so doesn’t become thick like wood part

Lateral Growth continued n n n Cork cambium forms outside the phloem and makes cork cells which fill with suberin – a waxy material that protect the trunk and branches The epidermis cracks off and the outside becomes the cork cells Bark = Phloem, Cork Cambium, Cork

Heartwood = dead, older xylem Sapwood = new xylem still carrying water Phloem – carries food - old phloem sloughs

Plant Transport nd 2 Plant Chapter 36

I. Local Transport (all review) Facilitated Diffusion A. a. b. c. Open channels Shape change channels (not regulared by ATP must by solutes moving thru) Gated channels Active Transport B. a. b. c. Normal Chemiosmosis – coupling the pumping of protons to the movement of other solutes (ex. Pump protons to cause the movement of K+ into guard cells) Co-transport – pumping protons, they attach to solutes and move them passively as they flow back thru the membrane Examples: 1. bringing nitrogen into the roots (pump H+ out of the epidermis into the soil and as it flows back it in brings nitrogen 2. loading sucrose into the phloem (pump H+ out of sieve tubes in phloem into the leaf mesophyll and it flows back bring sucrose with it) C. Osmosis – remember in plants, water doesn’t just move from high to low concentration, pressure also plays a role and can override solute and water concentration

Osmosis Continued Ψ = Ψp + Ψs n Water potential – the tendency for water to leave one place and go to another – the higher the Ψ the more likely water will leave and go somewhere else n Water moves from high to low water potential n Water potential = pressure potential + solute potential n n Pressure potential is usually positive created by the pressure exerted by the cell wall – the higher the pressure potential – the higher water potential Solute potential is 0 in pure water and negative if there any solutes - the more solutes the more negative solute potential and the lower the water potential – water moves where there is more solute!

II. Lateral Movement – short distance n n n There are three compartments within plant cells: Apoplast – continuum of cell walls Symplast – continuum of cytoplasm thru plasmodesmata Tonoplast – vacuole compartment set apart by the vacuole membrane – not continuous from cell to cell and the vacuole membrane can actively transport and do chemiosmosis Water and solutes can move through the apoplast, symplast, or into the tonoplast

Lateral Movement in Plants

III. Long Distance Transport (vertical movement thru xylem and phloem – diffusion is too slow A. Xylem (tracheids and vessel elements with 2 set of cells walls) - schlerenchyma ↑ ↑ Tracheids ↑ Vessel Element

Xylem Continued n n Water and mineral transported from roots to leaves To get into the xylem – things pass from the epidermis of the roots into the cortex and into the steele which then branches into the xylem in the stem In roots, root hairs increase surface area to absorb more thru the epidermis Endodermis (between cortex and steele) is selective in what mineral can cross into the steele

Xylem continued n Xylem has two methods of movement: n n Main method is transpiration accompanied by cohesion and adhesion (transpiration caused by lower water potential in air than in mesophyll of leaf) Second method that helps some is root pressure. Minerals are actively transported into the xylem in the root which decreases water potential in the xylem cells, water flows in and pushes the water up (only good for a few meters)

Movement of Water - Transpiration

Xylem continued n Regulation of Transpiration controls the flow of water thru the plant and also makes sure that the plant doesn’t dry out and have no water for photosynthesis n n n Guard cells buckle outward when full of water Guard cells flap closed when empty (when water is lacking, turgor pressure decreases and the cells become flaccid and flop together Also, guard cells use chemiosmosis to open and close n n They pump H+ out which causes a neg. charge inside that caused K+ to be drawn into the cell Due to the K+ in the cell – it become hypertonic and water flows in The active pumping is stimulated by light and low CO 2 For closing, K+ is transported out in response to high temp or high CO 2 (mediated by abscisic acid- a hormone)

Long Distance Transport Continued Phloem (sieve tubes and companion cells) B. Sugar is transported from the leaves to storage areas of the plant (roots and fruit) Phloem sap is mostly sugar in water but also contains aa, hormones, and some minerals Sugar will diffuse thru plasmodesmata from mesophyll cells to sieve tubes due to concentration difference Sugar is also actively transported into the sieve tubes making the sieve tube cells hypertonic so water rushes in and pushes the sugar water thru the phloem to needy areas Once in the phloem it moves from source to sink: • • At the sink end (no sugar), sugar is leaving the sieve tubes to go into storage cells by concentration differences This causes pressure to decrease and sugar flows high to low pressure and high to low concentration

Plant Nutrition rd 3 Plant Chapter 37

Plant Growth – where does the plant’s mass come from 1. Most of the plant weight is water n n n Water accumulates in vacuoles and elongates the cells and makes them turgid and acts as a solvent Water also supplies hygrogen which is incorporated into sugar in the Calvin Cycle 90% of a plant’s water is lost in transpiration and then replaced

Plant Growth Continued Of the dry weight – 95% is organic 2. § Most weight is CO 2 from the air that is incorporated into carbohydrates (remember most of structure is cell walls, made of cellulose which are strings of glucose) Of the dry weight – 5% is inorganic 3. § From minerals from the soil

Macronutrients (needed in lg. amts. ) Source of macronutrients: C, O → air H → water N, S, P, K, Ca, Mg → soil n n n Purpose of macronutrients: C, O, H – sugar and cell wall production N, S – make proteins N, P, - nucleic acids, ATP, phosphorylation cascades in cell signalling K – water balance, opening and closing stomates, cofactor for protein synthesis enyzmes Ca – membrane structure, formation of cell walls, cofactor Mg – part of chlorophyll n n n Micronutrients (needed is small amts. ) Fe, Cl, Cu, Mn, , B, Ni → all from soil, all used as cofactors n

Soil n n n n Soil is eroded rock and humus (dead organic stuff) and spaces for water Texture of soil determines the quality for certain plants Type of soil depends on how tightly packed - sand (loosest) → clay (tightest packed) A mix of soil types is the best Soil p. H affects the availability of minerals Soil often gets acidic from acid rain – put own lime which is basic – positve ions bind up negative ions and plants can’t get them from the soil Soils with a lot of clay bind up all the positive ions like K+, Ca++, Mg++, NH 4+ and it’s hard for plants to get. Negative minerals NO 3 -, PO 4 - don’t stay in the soil very long and wash away Some plants secrete H+ into soil which will compete for binding the to clay and release the postive mi nerals

Plants getting Nitrogen n Needed for aa and nucleic acids 80% of the air is nitrogen but N N, no enzymes in plants to break N 2 bond so it’s unuseable Plants get nitrogen from: n n n Decomposition of organic material to inorganic compounds that plants can absorb (NH 4+, NO 3 -, ammonium and nitrate) Nitrogen fixation – specialized bacteria (Rhizobium) which live free in soil or symbiotically on plant roots (legumes like peas, beans, soy, nuts) are able to convert N 2 into useable ammonium and nitrate Note: Some roots have leghemoglobin to bind O 2 for the bacteria to use because nitrogen fixation requires a lot of energy and the bacteria need a lot of oxygen for CR

Getting Nitrogen Denitrified by bacteria to N 2 – goes back into air - unusable Decomposed to Organic Material NH 4+, NO 3 Absorbed by plant roots OR x t ed Fi N 2 in air o Note – many times in farming – there is no decomposition so farmers add fertilizer – feces containing usable nitrogen cmpds. Getting Phosphorus Mycorrhizae – fungus living symbiotically on many plant roots, absorb PO 4 - and water and secrete plant root growth factors (in turn the plant feeds the non-photosynthetic fungus

Plant Adaptations to get minerals and water n n n Parasitic plants - do some photosythesis to make sugar but tap into other plants vascular system and suck out water and minerals Epiphytes – grow on other plants but are fully photosynthetic and not parastitic Carnivorous Plants – live in poor soil conditions – usually nitrogen deficient – capture animals for nitrogen and other minerals but are fully photosythetic for sugar (venus fly trap)

Farming Practices and Plants Crops are not Natural Crops remove minerals from soil but don’t decompose and return the organic or inorganic components to the soil 1. Must use fertilizers to replace N, P, K which then can run off and cause too much plant growth in rivers – clogging them and killing fish a. • b. Can use natural fertilizers which are slow release vs. commercial fertilizers which release faster but usually don’t stay in soil as long Can rotate crops – rotate with legumes – add nitrogen to soil and plow them under as fertilizer

Farming Continued Crops remove water from the soil 2. Ground aquifers collapse Many farmers irrigate with water containing salts – as the water evaporates, the soil becomes salty making the soil hypertonic (lower water potential) so water leaves the roots instead of entering n n 3. Crop harvesting causes the loss of top soil – soil blows or washes away once crops are harvested. Can combat problem by: q q Contour farming Not plowing at the end of the season Now planting in rows or plants that don’t grow in rows Planting crops that trap soil – rotating crops

Plant Signaling and Plant Hormones AP Biology Plant Class #4

Hormone Action The same hormone can have different effects depending on location, concentration, developmental stage or plant, etc. n n n n Effect Gene Expression Effect Enzyme Activity Change Membrane Properties Open Gated Channels Change Metabolism Stimulate Cell Division Affect the differentiation and development of cells

General Action of Hormones 1. 2. 3. 4. 5. Bind to receptors Receptors change shape in response to binding 2 nd messengers are activated which activate enzymes OR Directly activate or cause transcription of enzymes (particulary kinases which phosphorylate other enzymes) Enzymes ultimately: 1. 2. 3. 4. Activate gene transcription Activate transcription factors Deactivate transcriptional repressors Cause chemical reactions

Example of Plant Cell Signaling Response to a stem breaking through the ground for the first time Light activates Phytochromes (light receptor connected to a kinase) c. GMP activated Opens gated channels for Ca++ in cell membrane Enzymes are phosphorylated Calcium binds to Calmodulin Turn on transcription factors Activated kinases and turns on transcription factors Make Photosynthesis enzymes Make enzymes to make chlorophyll Make enzymes to decrease auxin production so don’t keep elongating the stems

Plant Hormones (internal signaling) Auxin n Produced by apical meristems, young leaves, developing seeds and fruit – generally moves from shoot to the base Moves through the parenchyma cells themselves – not vascular tissue - Transported by chemiosmosis In low conc. – causes cells to elongate faster n n n n Stimulates pumps to pump H+ into cell wall, ↓p. H activates enzymes that break down cell wall – allows water flowing in to expand wall Phototropism – growing toward light – elongates cells on dark side faster In high concentrations - induces ethylene gas which slows cell growth Control apical dominance Controls stem elongation in developing shoots Kills dicots/not monocots = pesticide for corn or grass fields Causes fruit to grow – if spray on plants, fruit will develop without seeds = seedless fruit

Cytokinins n n Produced by the roots, Moves through the xylem, modified adenine, named for cytokinesis since in actively growing parts of plant Stimulates cell division in roots, embryos, fruits, retards protein breakdown and prevents aging in leaves and fruits (florists spray on cut flowers to keep them fresh), stimulates seed germination Works with auxin, relative concentrations control growth and differentiation of plant parts Works opposite auxin to control height vs. bushiness (more auxin – grow tall, more cytokinins – more axillary buds – bushier)

Gibberellins n n n Produced in roots and young leaves Elongation and cell division in stems and leaves (activates enzymes that allow cellulose digesting enzymes to penetrate the cell wall) Cause germination of seeds – water stimulates release of gibberellins – stimulates production of amylase to break down carbs Important for pollen development, pollen tube growth Works with auxin for fruit growth (spray to make seedless grapes)

Abscisic Acid n n n Readies the plant for winter – slow growth of buds, inhibits growth Causes stomates to close in a wilting plant, opens the K+ channels so K+ leaves guard cells, water follows Keep seeds dormant when conditions not suitable (light, rain, etc. inactivates abscisic acid to cause seeds to germinate)

Ethylene n n n Gas – causes fruit ripening (breakdown of starch to sugar, breakdown of cell walls to soften, chlorophyll breaks down) Inhibits axillary growth in response to high auxin Causes leaf death in winter (can’t get water from frozen ground – don’t want to lose waterfrom leaves) Produced also in response to stress (drought, flood, infection) Destroys inside of xylem to make hollow tubes Plant growth in sprouting plant – when hits something solid – secretes ethylene – plant grows horizontally to escape object then turns upward again

Brassinosteriods n n n Cells elongation and division in stem (like auxin) Prevents leaves from falling off Promotes root growth at low conc. and stops root growth at high concentrations

Circadian Rhythms n n Fluctuations based on a 24 hour cycle – not due to environmental stimuli – based on some internal time clock Devoid of environmental clues – it deviates slightly from the 24 hour cycle (vary from 2127 hours)

External Signaling in Plants Light, Gravity, Mechanical Stimuli n n n Phototropism – growing toward sun (Auxin) Gravitropism – roots grow down, stems grow up (Auxin) Thigmotropism – change in growth due to mechanical stress (vines grow straight until contact – wrap around due to differential growth on opposite sides) Rapid Leaf Movements – loss of K+ causes water loss and leaves to fold up Sleep movements – transport K+ from 1 side of leaf to another – changing water flow Rubbing or touching a plant changes gene expression – can make plants shorter by rubbing the stem a couple of times a day

Plant response to light n Two types of light receptors n n n Blue light receivers Phytochromes – receive red light – photoreceptor linked to a kinase Photoperiodism – control of flowering and leaf growth by length of days n n n Short Day/Long Night – flower when light is shorter than a critical length (flower late summer) Long Day/Short Night – flower when light is longer than a critical length (flower in spring) Controlled by phytochromes – bound to a light absorbing molecule – light changes shape of phytochrome which change cellular responses)

Plant Response to Stress n Lack of Water n n n Lack of Oxygen (from overwatering – reduces air in soil) n n Some form air tubes in roots (ethylene causes cell death in ground cells in roots forming tubes, or roots are out of soil) Too much salt (causes water deficit) n n activate abscisic acid = K+ leaves and so does water – guard cells close Leaf growth inhibited due to lack of turgor pressure, so less water lost Make internal solutes to deep water potential lower in plant Heat (enzymes denature, water evaporates n n Transpiration for evaporative cooling Make heat shock proteins – may help prevent denaturation of proteins

Plant Response to Stress Continued n Cold n n n Herbivores n n n Plants increase amt. of unsat. Fatty acids in membrane to make them more fluid Change solute concentration in cells to prevent cooling with out ice crystals forming in cells Physical defenses – thorns, stickers Chemical toxins (ex. Make a weird aa that when incorporated into insect proteins – proteins are misshapen and the insects die) (ex. 2 – plant sends chemical signal in response to damage – signal causes wasps to come and inject eggs into catepillars eating the plant, wasp babies eat their way out) Infections n n Tough epidermis Phytoalexins and PR proteins – kill bacteria by dissolving their cell walls Express defense genes – apoptosis of infected cells, produce antibiotics Produce Salicylic Acid – makes cells resistant to attack