Stem Structure Bud Stem Petriole Internode Node

Leaf Structure Cuticle Protects from water loss, insect invasion, UV light Upper epidermis Palisade Mesophyll Additional protection Large number chloroplast Spongy Mesophyll Xylem Lightly packed – allows for gas exchange Transport water from roots Vein/ Vascular bundle Phloem Guard Cells Transport sugar to rest of plant Open/Close stomata Lower epidermis Stomata CO2(g) Gas exchange H2O(g)

Xylem Cells Dead Cells Thickened cellulose, lignified 2⁰ walls Strengthens cell walls Waterproofs plant Protects against pathogens Tapered to form continuous column Most modern plants Ancient plants Allows water to mover laterally

Stomata Operations Open/close due to cell turgor of guard cell Bulge to outside  opens Cell wall thickness uneven Caused by absisic acid (plant hormone) Blue light triggers ATP powered pumps Produced in root during water definicency K+ Causes K+ to move into guard cells CO2 levels circadian rhythms Higher solute = osmosis 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) Creates negative pressure 3. Vessel water column is maintained by cohesion/adhesion 4. Water is pulled from root cortex into xylem cells 5. Water is pulled from the soil into the roots

Root Structure Root Hairs: increase surface area = more absorption of water/minerals x3 Fully differentiated  functional cells 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 Removes humidity from stomata Increase kinetic energy - evaporation Cause guard cells to lose turgor – close stomata Reduces difference in water concentration gradient Less soil water, water stream stopped at roots, stomata close

Xerophytes thickened Crypt/pit – increases humidity Reduced number Decreases surface area for transpiration Trap water vapor, increases humidity Go dormant in dry months Alternative photosynthetic pathway CAM: stomata open at night Succulents – fleshy stems 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