Resource Acquisition and Transport in Vascular Plants

1. Resource Acquisition and Transport in Vascular Plants

2. Resource acquisition and transport

3. Transport review • Passive transport – no energy required, • ex. diffusion • Active transport – energy required • Transport proteins required, ex – proton pump • Uses energy from ATP to pump H+ across membrane • Cotransport– coupling of the steep gradient of one solute(H+) with a solute like sucrose • Drop in potential energy by H+ pays for transport of sucrose.

5. Water potential (potential grid problems) • Osmosis – movement of water across cell membrane via aquaporins • Water moves from area of high water potential to low potential • Water potential includes the effects of solute concentration and physical pressure.

6. Transpiration • Loss of water vapor from the leaves • Water and minerals are transported to rest of plant via bulk flow • Bulk flow is the movement of liquids in response to a pressure gradient • Rate of transpiration is regulated by stomata

7. Stomata • Pore in leaf epidermis with guard cells on each side. • Water enters guard cells, following K+, turgor pressure increases, stoma opens and vise versa • Stomata open and close in respond to environmental signals

8. Cohesion-tension hypothesis • Transpiration provides the pull for the ascent of water. • Water is lost due to lower water potential of the air • Cohesion of water molecules via hydrogen bonds plus adhesion of water to plant cell walls form a water column.

9. Organic nutrient transport • Girdling – removing bark form tree, accumulation of sugar • Pressure flow model – 29.22 • Sugar enters the sieve tubes (active transport) and creates positive pressure, phloem begins to flow • Roots are a sink – provide place for sugar to be used for cellular activities (respiration) • Source to sink – leaves to roots or any place that needs sugar (new leaves…)

10. Soil and Plant Nutrition • 95% of plant’s dry weight (biomass) is carbon, hydrogen, and oxygen (carbohydrates, CO2 and water) • Minerals – provide proteins and nucleic acids • Essential nutrients – has role, no substitute, and a deficiency results in death. • Macro and micronutrients according to concentration • Beneficial nutrients – required or enhances growth

11. Mutualistic relationships • Nitrogen-fixing bacteria – root nodules of legume plants • Fix atmospheric nitrogen into a form that plants can use, plants provide food to bacteria • Mycorrhizae – plant roots and fungi, plants give fungus food, fungus increases surface area for water uptake and minerals

12. Symbiotic relationships that arenot mutualistic • Parasitic plants (dodder), does not undergo photosynthesis, needs other plants for nutrients • Epiphytes – grown on surface of other plants instead of soil, not parasitic, ex. orchids • Carnivorous – photosynthetic but get some nitrogen and minerals from small animals