Stem Structure Bud Stem Petriole Internode Node

Leaf Structure CuticleProtects from water loss, insect invasion, UV light Upper epidermis Additional protection Xylem Transport water from roots Phloem Transport sugar to rest of plant Vein/ Vascular bundle Lower epidermis Palisade Mesophyll Large number chloroplast Spongy Mesophyll Lightly packed – allows for gas exchange Guard Cells Open/Close stomata Stomata Gas exchange CO 2 (g) H 2 O(g)

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

Stomata Operations Open/close due to cell turgor of guard cell Cell wall thickness uneven Bulge to outside  opens Blue light triggers ATP powered pumps Causes K+ to move into guard cells Higher solute = osmosis K+ Caused by absisic acid (plant hormone) Produced in root during water definicency Cells sag due to water loss (close) CO 2 levels circadian rhythms

Transpiration Cohesion-Tension Theory 1. Water moves down concentration gradient (out of plant) 2. Water lost by transpiration is replaced by water from xylem 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 Creates negative pressure

Root Structure Root Hairs: increase surface area = more absorption of water/minerals x3 Protects apical meristem Zone of cell division (M phase) ‘Stem’ cells – undifferentiated cells Enlarging cells (G1 phase) Start differentiating Fully differentiated  functional cells

Cross Section of Root Vascular Bundle Root Hair Epidermis Endodermis Xylem Pericycle Phloem Cortex Water movement: due to osmosis (higher solute concentration inside root)

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 Water and Minerals All particles need to go symplastic at endodermis to get to xylem 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 Reduces difference in water concentration gradient Less soil water, water stream stopped at roots, stomata close Cause guard cells to lose turgor – close stomata

Xerophytes thickened Trap water vapor, increases humidity Reduced number Crypt/pit – increases humidity Decreases surface area for transpiration Succulents – fleshy stems Go dormant in dry months Alternative photosynthetic pathway CAM: stomata open at night C 4 : rapid uptake of CO 2

Halophytes: high levels of salinity Sunken stomata Leaf surface area reduced Succulents: dilute salt concentration Salt glands: secrete salt Compartmentalize Na + and Cl - in vacuoles Prevents salt toxicity

In your groups Read transpiration lab Design how you want to conduct the experiment. Rough draft write up Friday you will conduct this experiment. P 392 in your book will help. You need to copy that chart in your results.