Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Cell growth wikipedia , lookup
Cytokinesis wikipedia , lookup
Endomembrane system wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cell culture wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cellular differentiation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
List of types of proteins wikipedia , lookup
III. Angiosperm Anatomy and Physiology A. Kinds of Plant Tissue 1. Meristem- One of two types of plant tissue capable of carrying on mitosis a) Root meristem- tissues near the tip of the root responsible for downward growth b) Apical meristem- tissue near the tip of a stem that produces upward growth c) The lengthening of the roots and stems is called primary growth. d) Cell produced by the meristem are all alike until they go through differentiation. This process converts them to specialized tissues: Epidermis, Vascular and ground tissue 2) Cambium-tissue responsible for secondary growth- the widening of roots and stems 3) Epidermis- outermost layer of cells that develop into a protective layer that produces cutin- waxy material that prevents water loss 4) Vascular tissue- tissue that transports food and water A) Xylem- dead hollow cells that transport water and provide strength B) Phloem- tissue that transports food (glucose) 5) Ground tissue- tissues for the storage of food and the protection of vascular tissue A) Cortex- food storage cells B) Endodermis- cells that determine what enter the vascular tissue B. Angiosperm Organs 1. Roots a) Functions: 1) Absorb water and minerals 2) Anchor the plant 3) Store food in the form of starch b. Root Morphology (external structure) 1) Taproot- one large vertical root. Found in many dicots and provides firm anchorage. Can be modified to store a large amount of food 2) Fibrous Root3) Adventitious highly branched, thin Roots- arise from the root. Provides a large stem and leaves area for water and mineral absorption. Found in many monocots c. Root Growth & Structure 1) Zone of Differentiation: Cells become different tissues. (Outer cells become epidermis. Inner cells become vascular tissue and the cells in between become cortex) 2) Zone of Elongation- cells become full sized and drive the root cap downward into the soil 3) Zone of Cell division root meristem is here. Contains quiescent center 4) Root cap- protects inner cells from damage. The smashed cells produce a slimy coat that helps ground penetration d. Cross Section of a Root 1) Epidermisprotection 2) Root hairincrease surface area for water absorption 3) Cortex- food storage 4) Phloem- food transport 5) Xylem- water transport 2. Stems a) Functions: 1) transport food, water and minerals between the roots and the leaves. 2) support the plant growth above ground b) Stem Morphology Herbaceous Stem Woody Stem 1. Herbaceous Stems a) Soft, green and fleshy with little or no secondary growth b) Stem is supported by the water that fills their central vacuoles called turgor pressure and the slight lignification of their cell walls 2. Woody Stems a) Most dicots and gymnosperms produce woody stems which are hard and long b) Woody stems have a vascular cambium that allows for secondary growth (width) c) The vascular cambium adds phloem cells towards the outside and xylem cells to the inside d) The xylem added each year forms the tree rings Woody Stems e) The xylem that conducts water is called sapwood. f) The older xylem in the middle that is non-functioning is called heart wood. g) Woody stems have a cork cambium which fills in the gaps in the bark caused by the yearly addition of xylem h) Bark is not air tight, gaps called lenticels allow gas exchange c. Structure of Stems 1. In the stem, the vascular tissues are arranged into groupings called Vascular Bundles a) Monocotsvascular bundles are in a random order b) Dicots- vascular bundles are arranged in a ring between the pith and the cortex Which is the Monocot and which is the Dicot stem? 2. Buds and Branches a) Buds protect the apical meristem from freezing and drying during the winter b) Buds develop in the fall and consist of 3 basic parts: Bud Scales Embryonic leaves Apical Meristem c) Bud scales- protect the meristem in the winter. When the bud absorbs water in the spring, it swells and the scales fall off leaving scars I d) Terminal buds: at the n end of stems t e e) Lateral buds: project r from the sides of stems n o f) The distance between d bud scale scars is e called an internode which equals one year g) Apical Dominance- the presence of a terminal bud inhibits the auxillary buds 3. Modified Stems a) Stolons- horizontal stem growing along the surface of the ground. Ie. Strawberries b) Rhizomes- horizontal stem underground. Ie Irises and Irish potatoes c) Bulbs- vertical underground shoots with leaves modified for food storage. Ie. Onion 3. Leaves a. Function: organs that have the ability to make food (glucose) in photosynthesis (Leaves stomates) (Enters stomates) (From Roots) (To Roots) b. Structure of the leaf Leaf Parts 1. Cuticle- waxy layer that prevents water loss 2. Palisade layer- major photosynthetic layer 3. Upper Epidermis- protects underlying cells and secretes cuticle 4. Chloroplast- organelle responsible for photosynthesis 5. Spongy Layer- allow gas exchange and moves food to phloem 6. Lower epidermis- protection, contain stomates for gas exchange Leaf Parts 7. Guard Cells- flank stomates and open and close them 8. Stomate- gap through which air actually passes 9. Phloem- carries food 10. Xylem- carries water 11. Vein- holds xylem and phloem C. Transport in Vascular Plants 1. Transport at the Cellular Level a) Passive Transport- doesn’t require cellular energy input 1) Diffusion- solutes move down the concentration gradient from areas of high concentration to areas of low concentration 2) Facilitated Diffusion- protein form selective channels to allow specific solutes through the membrane 3) Osmosis- the diffusion of water from areas of high water potential to low water potential b) Active Transport- requires energy input from the cell 1) Transport Proteins- embedded in the cell membrane bind to a specific substrate, change conformation and release the substrate on the other side of the membrane 2) Proton Pumps- hydrolyze ATP and use the energy to pump protons across membrane to create an electrochemical gradient • • Cations will be driven into the cell by membrane potential Anions are accumulated by the cell through cotransport with hydrogen ions 2. Short Distance (Lateral) Transport a) From Cell to Cell- out of one cell through the cell membrane and cell wall into the next cell through the cell membrane and cell wall b) Symplast- a continuum of cytoplasm within the plant formed by plasmodesmata- cytoplasmic channels formed through pores in the cell wall c) Apoplast- the extracellular pathway between cell walls 3. Pathway of Water and Minerals a) Water and dissolved solutes gain access to the roots through root hairs with hydrophilic cell walls b) Water and minerals enter apoplastic routes; however, the entrance to the stele is blocked by a ring of wax called the casparian strip which lies tangential to the stele c) Minerals must be extracted from the extracellular fluid into cortex cells and follow a symplastic pathway into the stele d) Therefore, the endodermal cells regulate the composition of the sap SoilEpidermisCortex EndodermisStele 4. Transpiration-Cohesion-Tension Mechanism a) Transpiration- water evaporates out of the leaf through the stomate. This causes water to leave the cells surrounding the air spaces in the leaf. b) The tension, or negative pressure causes water to move from the xylem in the leaf petiole to the cells. c) Cohesion- hydrogen bonding between water molecules pulls water up the stem from the root to replace water lost by the leaf d) Adhesion- water molecule clings to xylem cell walls which prevents back flow due to gravity. e) Root Pressure- water is pushed up the root xylem tubes as water enters the root hairs f) Plants can regulate transpiration by opening or closing stomates 5. Control of Transpiration (Plants strike a balance between gas exchange and water loss. When stomates are open, both gas exchange and water loss are greatest) a) Guard cells flank stomata and control stomatal diameter by changing shape 1) When turgid, guard cells buckle due to microfibrils. This causes the stomate to open 2) When flaccid, guard cells sag and close stomate b) Change in turgor pressure is accomplished by the uptake of potassium ions 1) Uptake of potassium lowers water potential causing water to enter 2) Closing occurs when potassium ions leave c) Stomates open at dawn because: 1) Light induces guard cells to uptake potassium due to the activation of a light receptor which activates proton pumps in the plasma membrane 2) Decrease in carbon dioxide in the leaf air space due to photosynthesis in the mesophyll 3) Internal clocks in the guard cells d) Guard cells will close if: 1) Water deficiency results in flaccid guard cells 2) Production of abscisic acid by mesophyll cells 3) High temperature increases carbon dioxide in the leaf air space due to increased respiration 6. Transport in Phloem a) Translocation- process of transporting sugar from a source to a sink through phloem 1) Source- sugar producing cells 2) Sink- cell requiring sugar b) Loading sugar from a source 1) Sugar may be loaded via the symplast 2) Proton pumps can actively load sugar against the concentration gradient c) Increased sugar concentration lowers water potential which causes water from the surrounding tissues to enter the phloem d). The resulting increase in pressure drives the sap to the sink cell. This is called bulk flow IV. Nutrition in Plants A. Nutrition Requirements in Plants 1. Water- the most abundant compound in most plants is an essential nutrient for photosynthesis 2. Carbon dioxide- is incorporated into a plants organic material 3. Minerals- (inorganic ions) are selectively absorbed by the roots 4. Macronutrients- needed in large amounts 5. Micronutrients- are needed in small quantities Macronutrients Micronutrients B. Nitrogen Assimilation in Plants 1. Plant growth and crop yield are often limited by nitrogen, an essential ingredient of proteins and nucleic acids 2. Although the atmosphere is rich in nitrogen, plants require the assistance of bacteria living in soild to supply them with the forms of nitrogen they need a) Nitrogen-fixing bacteria posses nitrogenase an enzyme that converts atmospheric nitrogen into ammonia b) The ammonia is then converted to nitrate or ammonium, which can be used by the plant 3. The roots of legumes have nodular swellings that house the nitrogen-fixing bacteria 4. Improving the quality and quantity of protein crops and can help alleviate the problem of human malnutrition 5. Agricultural research in developing protein-rich plants and enhancing nitrogen-fixing capabilities may yield practical benefits to the world C. Some Nutritional Adaptations in Plants 1. Parasitic Plants- either supplement their photosynthetic nutrition or give up photosynthesis entirely by tapping the vascular system of the host plant Nutritional Adaptations 2. Carnivorous Plantsusually found in poor soil or acid bogs. Obtain nitrogen by killing and digesting insects Nutritional Adaptations 3. Mycorrhizaemutualistic associations between root and fungi help the plant by enhancing mineral nutrition, water absorption and disease resistance