BIO 123- Week 1 Notes
BIO 123- Week 1 Notes BIO 123
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This 3 page Class Notes was uploaded by Tiffany Liao on Tuesday February 2, 2016. The Class Notes belongs to BIO 123 at Syracuse University taught by Jason Wiles in Winter 2016. Since its upload, it has received 30 views. For similar materials see General Biology II in Biology at Syracuse University.
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Date Created: 02/02/16
Jan 27, 2016 Leaf tissue anatomy- Epidermis- covers upper, lower surfaces of leaf blade Waxy cuticle coats epidermis- helps plants survive dry terrestrial conditions Stomata- Small pores in epidermis, which permit gas exchange for photosynthesis - Surrounded by two guard cells and often associated with special epidermal cells (subsidiary cells) Eudicot and monocot guard cells Mesophyll- photosynthetic parenchyma cells a. Palisade mesophyll- functions primarily for photosynthesis b. Spongy mesophyll- functions primarily for gas exchange - Water vapor escape through stomata Veins- Xylem- conducts water and essential minerals to leaf Phloem- conducts sugar produced by photosynthesis to rest of plant Monocot leaves- Have parallel venation Dicot leaves- Netted venation Adaptations for photosynthesis- - Most leaves have broad, flattened blade- efficient in collecting sun’s radiant energy - Stomata open during day – for gas exchange needed in photosynthesis. Close at night to conserve water when photosynthesis is not occurring * Except for in CAM plants (usually arid environments) then, the stomata open at night - Transparent epidermis- allow light to penetrate into middle of leaf, where photosynthesis occurs Transpiration- loss of water vapor from aerial parts of plants- occurs primarily through stomata - Rate of transpiration affected by environmental factors- temperature, wind, relative humidity - Effect of transpiration- Both beneficial and harmful to plant Trade-off between- CO2 requirement for photosynthesis – need for water conservation Leaf abscission- - Loss of leaves- as winter approaches in temperature climates – at beginning of dry period in tropical climates with wet and dry seasons - Complex process- physiological and anatomical changes occur prior to leaf fall Leaf derived adaptation- Spines Tendrils Bud Scales Bulbs Succulent leaves Carnivorous plants - Some leaves are modified for special functions in addition to photosynthesis and transpiration Stems- Monocot stem where vascular bundles are scattered Eudicot stem where vascular bundles are in a distinct ring form ( pith, cortex) Node- area on stem where leaf is attached Internode- region of stem between two nodes Vascular cambium- - Lateral meristem that produces periderm- cork parenchyma and cork cells - Cork cells- replaces epidermis in a woody stem - Cork parenchyma- primarily for storage BIO NOTE Feb 1, 2016 Water movement- - Water and dissolved minerals move from soil into root tissues (epidermis, cortex) - Water and minerals move upward, from root xylem to stem xylem to leaf xylem - Water entering leaf exits leaf veins and passes into atmosphere Tension-Cohesion Model- Explains rise of water-even in the tallest plants Transpiration- - Evaporative pull causes tension at top of plant - Result of water potential gradient - Ranges form slightly negative in soil and roots to very negative in atmosphere - Column of water pulled up through the plant remains unbroken due to cohesive and adhesive properties of water Root pressure- - Explains rise of water in smaller plants- particularly when soil is wet - Pushes water up through xylem- water moves form soil into roots due to active absorption of mineral ions form soil Sugar translocation- Dissolved sugar is translocated upward or downward in phloem - From area of excess sugar (usually leaf) - To a sink (area of storage or sugar use: roots, apical meristems, fruits, seeds) Sucrose is the predominant sugar translocate in phloem Pressure-Flow Hypothesis- - Explains movement of materials in phloem - Companion cells actively load sugar into sieve tubes at source- requires ATP - Sugar accumulates in sieve tube - Companion cells unload sugar from sieve tubes at sink- actively (requiring ATP) and passively (not requiring ATP) - Water leaves sieve tubes by osmosis- decreasing turgor pressure (hydrostatic pressure) inside sieve tubes Turgor pressure gradient- - Produced by water entering phloem at source and water leaving phloem at sink - Drives flow of materials between source and sink Taproot and Fibrous root Taproot system- has one main root - Formed from the radicle - From which many lateral roots extend
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