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Copyright Notice! This PowerPoint slide set is copyrighted by Ross Koning and is thereby preserved for all to use from plantphys.info for as long as that website is available. Images lacking photo credits are mine and, as long as you are engaged in non-profit educational missions, you have my permission to use my images and slides in your teaching. However, please notice that some of the images in these slides have an associated URL photo credit to provide you with the location of their original source within internet cyberspace. Those images may have separate copyright protection. If you are seeking permission for use of those images, you need to consult the original sources for such permission; they are NOT mine to give you permission. ©1996 Norton Presentation Maker, W. W. Norton & Company Radish seedlings have roots with long root hairs that increase the surface area for water and mineral uptake Dicot Mature Root Structure - Anatomy Ranunculus acris - buttercup Epidermis Cortex Storage of starch Vascular Cylinder Selective mineral uptake and conduction Make root hairs for cation exchange Root Vascular Cylinder and Cortex Storage of Starch, etc. Cortex Sieve Tube Cell conducts organic molecules Ranunculus acris - buttercup Endodermis Companion Cell keeps the sieve tube cell alive! Selective mineral uptake via these “window cells” Phloem Xylem Conducts minerals and water up to shoot system Divides to make branch roots Pericycle Xylem cells lack cytosol when mature and functional, and thus are dead. Which human parts are made of dead cells at maturity? A. Hair shafts. B. Finger nails. C. Epidermal surface cells. D. All of these are dead at maturity. Osmosis: passive movement of water from pure to saltier area cell membrane cell wall Do solutes cross the membrane? Virtually not; the bilayer is impermeable to solutes, and transport proteins keep solutes concentrated in the cell water flow cytoplasmic solutes more concentrated soil solutes more dilute Water potential low Water potential high This passive movement obeys the 2nd Law of Thermodynamics! Root hairs are responsible for cation exchange cortex cell epidermal cell root hair penetrates soil spaces intercellular gas space Ca2+Ca H 2+ soil particles covered with capillary water and minerals + to endodermis and vascular cylinder then up the xylem to the shoot Ca2+ H+ voids with air space water Fig. 39.7-8 pp. 781-2 Root Vascular Cylinder and Cortex Storage of Starch, etc. Cortex Sieve Tube Cell conducts organic molecules Ranunculus acris - buttercup Endodermis Companion Cell keeps the sieve tube cell alive! Selective mineral uptake via these “window cells” Phloem Xylem Conducts minerals and water up to shoot system Divides to make branch roots Pericycle endodermis xylem inside The endodermis is thus responsible for selective mineral uptake. suberinwaxy barrier to apoplastic movement cortex outside minerals cannot go between cells minerals must go through cells cell membrane proteins (active transporters) determine which minerals may be taken up Important?: All human minerals in food come via this path! Mineral uptake: Active transport against concentration gradient cell membrane cell wall Calcium transport protein ADP + Pi Ca2+ too expensive? Ca2+ Ca2+ ATP Possible solute diffusion gradient water flow cytoplasmic solutes more concentrated Water potential low soil solutes more dilute Water potential high Osmosis: passive movement of water from pure to salty area Which tissue conducts water and soil minerals up the plant? A. B. C. D. E. F. Epidermis. Cortex. Endodermis. Pericycle. Phloem. Xylem. This is a cross-section of a “typical” leaf: Syringa vulgaris (lilac) soil mineral entry evaporative cooling means the solute concentration increases! Element Concentration Solute availability is pH dependent iron 4 acidic nitrogen 7 neutral pH of soil water The optimal pH? molybdenum alkaline 10 Which pH would be optimal (ideal) for mineral availability? A. B. C. D. E. 4. A little below 7. 7. A little above 7. 10. Element Concentration Solute availability is pH dependent iron 4 acidic nitrogen optimum 7 neutral pH of soil water molybdenum alkaline 10 ©1996 Norton Presentation Maker, W. W. Norton & Company Soil pH is less than 4 Dionaea (Venus’ fly trap) leaves have evolved three trip hairs on each half-blade, an electrical potential is produced, osmosis causes the trap to snap shut, This fly is about to touch the second trip hair… ©1996 Norton Presentation Maker, W. W. Norton & Company The trap halves have folded together, and the marginal spines have turned inward…the compound action makes an effective trap…have you ever tried to catch a fly? ©1996 Norton Presentation Maker, W. W. Norton & Company Saracennia (pitcher plant) leaves hold water to drown insects and mine their minerals Soil pH is less than 4 Remember that carnivorous plants are not eating insects for energy or carbon… they are mining the insects for minerals unavailable from the acidic bog soil. ©1996 Norton Presentation Maker, W. W. Norton & Company Drosera (sundew) uses sticky pads that look like nectaries but are actually glandular hairs secreting botanical “super glue” with digestive enzymes: Mycorrhizal fungi assist with nutrient uptake fungal mycelium ©1996 Norton Presentation Maker, W. W. Norton & Company root Can you distinguish heterocysts and vegetative cells? ©1996 Norton Presentation Maker, W. W. Norton & Company Anabaena heterocysts fix nitrogen and support bacterial growth as amino acids (organic nitrogen) leaks out into the surrounding water…vegetative cells provide carbohydrate too. http://www.interet-general.info/IMG/rhizobium-nodule-1.jpg Rhizobium needs anaerobic conditions to convert N2 into NH4+. Legumes produce heme based molecules and have rapid respiration to eliminate oxygen from root nodules that house the bacterial “symbiosis.” ©1996 Norton Presentation Maker, W. W. Norton & Company Here are legumes with Rhizobium and without Rhizobium But shrubs also generally have some compromise for uprooting forces…feeder roots extending laterally. In shrubs like this tea plant (Camellia sinensis), the root system will be more tap root than fibrous root. Notice the diameter of this tap root compared to this man’s waist! Tropical soils are nutrient-poor. Roots must traverse the surface for minerals, so roots grow on the surface (no tap root). So, to keep this tree standing upright, the roots grow in diameter but only in the vertical dimensions to form ridge roots…called buttress roots. These roots inspired gothic cathedral architects to design buttress walls. How do buttress roots work? Buttress roots inspired supports for long city walls and cathedral walls to prevent collapse. http://www.oxc.com.hk/raoul_nathalie/gallery/images/04%20Buttress.jpg http://www.dublincity.ie/dublin/citywalls/buttress.jpg The foundation is critical! Prop roots such as these inspired flying buttresses. Pandanus utilis - screw pine http://williamcalvin.com/BHM/img/FlyingButtressND.jpg http://www.contrib.andrew.cmu.edu/~ajm/Pages/Graphics/flyingbuttress.JPG