BIO 123 1st Edition Lecture 3Outline of Last Lecture I. Parts of a Leafa. Leaf Anatomyb. Leaf FormsII. Adaptations for PhotosynthesisIII. TranspirationIV. Leaf AbscissionV. StemsOutline of Lecture 3I. Water MovementII. Root Pressurea. Sugar Trans locationb. Pressure-Flow HypothesesIII. Root SystemsIV. Plant Structures V. Root TypesLecture 3 I. Water Movementa. Water and dissolved materials move from soil into root tissue (epidermis and cortex)b. Water and dissolved materials moves up > Root Xylem > Stem Xylem > Leaf Xylemc. Water enters leaf, exits leaf veins, into the atmosphere Tension Cohort Model 1These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Rise of water, even in tall plants - Transpirationo Evaporative pull causes tension at top of planto Result of water potential gradiento (Ranges from slightly negative in soil and roots to very negative in atmosphere) Tension Cohort Model 1o Column of water pulled up through the plant remains unbroken - Due to cohesive and adhesive properties of waterKey Concept: According to the tension–cohesion model, transpiration pulls water up through thestem as water evaporates from leaves by transpiration.II. Root Pressureo Explains rise of water in smaller plants particularly when soil is weto Pushes water up through xylem- Water moves from soil into roots due to active absorption of mineral ions from soil Sugar Translocationo Dissolved sugar is trans located upward or downward in phloem- From area of excess sugar (usually a leaf) - To a sink (area of storage or sugar use: roots, apical meristems, fruits, seeds)o Sucrose is the predominant sugar trans located in phloemIII. Pressure - Flow Hypothesis 1o Explains material movement in phloemo Companion cells actively load sugar into sieve tubes at source- Requires ATP Pressure - Flow Hypothesis 2o Sugar accumulates in sieve tube element - Causing movement of water into sieve tubes by osmosis Pressure - Flow Hypothesis 3These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Companion cells unload sugar from sieve tubes at sink- Actively (requiring ATP) and passively (not requiring ATP)o Water leaves sieve tubes by osmosis- Decreasing turgor pressure (hydrostatic pressure) inside sieve tubes Pressure - Flow Hypothesis 4o Turgor pressure gradient Produced by water entering phloem at source and water leaving phloem at sink Drives flow of materials between source and sinkIII. Root Systems o Underground, obtain water and dissolved materials, anchor.  Taprooto Has 1 main rooto Formed from the radicleo From which has many lateral roots extended Fibrouso Has many adventitious roots of same size Developing from end of stem Lateral root branch from adventitious rootsRoot Structures Root Cap- Protective layer that covers the root top - Covers delicate root apical meristem- May orient root so that is grows downward Epidermiso Protects the root Root Hairso Short-lived extensions of epidermal cellsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Help absorb water and dissolved minerals Stele - vascular cylinder Pericycleo Gives rise to lateral roots, lateral meristems Xylemo Conducts water and dissolved minerals Phloemo Conducts dissolved sugarKey concept: The endodermis absorbs mineral ions from the soil solution by an active, energy requiring process.Root TypesI. Prop Rootso Develop from branches or vertical stemo Grow downward into soil- Helps support certain plants in upright positionII. Mycorrhizaeo Mutually beneficial associations between roots and soil fungiIII. Root Noduleso Swelling on roots of leguminous plantso House rhizobia (nitrogen-fixing bacteria)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a