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An underdeveloped stem/leaf/flower Stem Structure Bud So if Nodes are crucial “organs” of the plant, then the internodes are like the blood vessels that carry water from node to node. Stem Is the stalk that Petriole attaches the leaf to the stem. Internode Space between nodes. Point on a stem Node where the buds, leaves and branching twigs split. Leaf Structure Waxy layer that protects against water loss, insects and UV light Additional protection. Large number of chloroplast (to Transports carry out photosynthesis. water to the leaves Lightly packed chloroplasts, allows for gas exchange. O and CO2 exchange with environment. Controls the open/closing of stoma. Carries the products of photosynthesi s to the rest of the plant. Xylem Cells Dead Cells Thickened cellulose, lignified secondary walls Strengthens cell walls Waterproofs plant Protects against pathogens Tapered to form continuous column Most modern plants Allows water to mover laterally Ancient plants Stomata Operations Open/close due to cell turgor of guard cell Guard Cells bulge to outside, when take in water opens Blue light triggers ATP powered pumps Causes K+ to move into guard cells Higher solute = osmosis Video Cell wall thickness uneven Loss water, cells sage towards each other. K+ K+ is forced out byabsisic acid (plant hormone) Produced in root during water deficiency Other Regulators of open/close: CO2 levels circadian rhythms Cells sag due to water loss (close) Transpiration Cohesion-Tension Theory 2. Water lost by transpiration is replaced by water from xylem 1. Water moves down concentration gradient (out of plant) into atmosphere, which has low water concentration. 3. Vessel water column is maintained by cohesion/adhesion Cohesion: H bond to form water. Adhesion: water bond to sides of vessels. 4. Water is pulled from root cortex into xylem cells Cohesion and Adhesion maintain columns under the tension created by transpiration. 5. Water is pulled from the soil into the roots. Created from tension created by transpiration. Root Structure Fully differentiated functional cells Root Hairs: increase surface area = more absorption of water/minerals x3 Enlarging cells (G1 phase) Start differentiating Zone of cell division (M phase) ‘Stem’ cells – undifferentiated cells Protects apical meristem Cross Section of Root Water movement: due to osmosis (higher solute concentration inside root) Root Hair Epidermis Endodermis Xylem Vascular Bundle Pericycle Phloem Cortex Mineral Ion Movement Fungal Hyphae: symbiotic relationship Increases surface area for absorption Active Transport: high concentration of solute in root Need more or ion cannot pass lipid bilayer hypertonic situation Diffusion of mineral ions by mass flow of water Passively flow due to low solute concentration in root Movement within roots All particles need to go symplastic at endodermis to get to xylem Water and Minerals Movement between cell walls Movement within cells – water/minerals pass through plasmodesmata Factors that affect transpiration Increase evaporation Reduces difference in water concentration gradient Removes humidity from stomata Less soil water, water stream stopped at roots, stomata close Increase kinetic energy - evaporation Cause guard cells to lose turgor – close stomata Xerophytes thickened Crypt/pit – increases humidity Reduced number Trap water vapor, increases humidity Decreases surface area for transpiration Go dormant in dry months Succulents – fleshy stems Alternative photosynthetic pathway CAM: stomata open at night C4: rapid uptake of CO2 Halophytes: high levels of salinity Sunken stomata Leaf surface area reduced Succulents: dilute salt concentration Compartmentalize Na+ and Cl- in vacuoles Prevents salt toxicity Salt glands: secrete salt