Transport in Angiosperms

1. Transport in Angiosperms Chapter 36 36.3, 36.4, 36.5

2. Root systems have a large surface area for anchorage, water, and mineral ion uptake. Shallow roots provide anchorage and collect surface water runoff or nutrients close to the soil surface Branching root systems maximize surface area for absorption. Dicot tap roots reach deeper into the soil to absorb water and minerals

3. Root systems have a large surface area for anchorage, water, and mineral ion uptake. Root hairs increase the surface area further still.

4. Root Absorption Animation

5. Water and mineral ions must first travel to the roots before they are taken up. • Diffusion of mineral ions • As mineral ions are absorbed a small concentration gradient is generated. • Mineral ions diffuse slowly toward the root

6. Water and mineral ions must first travel to the roots before they are taken up. • Fungal hyphae • A mutualistic relationship between some plants and fungi exists. • Fungi produce mycelium, a network in and around roots that increases concentration of ions (phosphate & nitrates)

7. Water and mineral ions must first travel to the roots before they are taken up. What do the fungi get from this mutualistic relationship? Sugars from the plant!!

8. Water and mineral ions must first travel to the roots before they are taken up. • Mass Flow • As water flows through the soil it carries minerals with it in solution. • A hydrostatic gradient is created by uptake of water at the roots. Water & solutes are sucked up (slowly)! H2O

9. Mineral Ion Absorption. Active transport of mineral ions occurs at root hairs. Cations – Positively charged Ca2+ & K+ by ion exchange using a proton pump. Anions – Negatively charged NO3- by symport with H+ ions. Anions Cations

10. Figure 36.7a Explain 2 things happening here. (a) H+ and membrane potential EXTRACELLULAR FLUID CYTOPLASM  + H+ Hydrogen ion  + ATP  + H+ H+ H+ H+ H+ H+  + H+ Proton pump  + Proton pumps create a membrane potential Proton pumps establish a pH gradient across the membrane. These two forms of potential energy can drive the transport of molecules.

11. Explain what is happening here. Figure 36.7b  + H+ H+ S  H+ + H+  H+ + H+ H+ S S H+ H+ H+ S S S  + H+  + Sucrose(neutral solute) H+/sucrosecotransporter  + Neutral solutes such as sugars can be loaded into plant cells by cotransport with H+ ions

12. Explain what is happening here. Figure 36.7c  + H+ H+ NO3  + NO3 H+  + H+ H+ H+ Nitrate H+ H+ NO3 NO3 NO3  + NO3  + H+ H+NO3cotransporter H+ H+  + Cotransport mechanisms involving H+ drive the uptake of NO3- by plant roots.

13. Explain what is happening here. Figure 36.7d  + Potassium ion K+  + K+  + K+ K+ K+ K+ K+  + Ion channel  + Plant ion channels open and close in response to voltage, stretching the membrane.. When open specific ions can diffuse across.

14. Root Osmosis Video

15. Support of Terrestrial Plants • Plants are supported in three ways: • Cell Turgor • Lignified Xylem • Thickened Cellulose

16. Turgor pressure- the pressure inside the cell on the cell wall by the plasma membrane due to water that has entered the cell by osmosis.  

17. Lignified Xylem – for added support lignin rings are present periodically through the length of the stem.

18. Lignified Xylem Micrograph of xylem

19. Thickened cellulose– cellulose in the cell wall is thicker relative to cell size near the outer edge of the stem. Thickened cellulose.

20. Transpiration Can you define it? • The loss of water from the leaves and stems of plants. • Xylem vessels transport water through the plant (remember water’s cohesive & adhesive properties).

21. What drives the process of transpiration? Fig. 36.12

22. Transpiration • Transpiration Process: • Water is heated in the mesophyll by sunlight and becomes vapor. • The vapor transpires out of the stomata (pour in the leaf). • Loss of water generates negative pressure and a transpiration pull on water molecules in the xylem. More water is drawn into the leaf.

23. Fig 36.13

24. Transpiration • Transpiration Process: • Cohesion between water molecules means that the transpiration pull has an effect throughout the plant. • Higher rates of transpiration lead to a faster transpiration stream& higher rates of water uptake. • This theory is known as cohesion tension theory.

25. Transpiration • Transpiration flow - occurs through the Xylem

26. Transpiration Pits between xylem vessels allow sideways movement of water and ions. • Transpiration flow - occurs through the Xylem Upwards movement in the xylem is generated by the transpiration pull: cohesion between water molecules allows water to be ‘sucked up’ Water to be ‘sucked up’ adhesion is the attraction between water molecules and the cellulose in the plant cell wall.

27. Transpiration • Transpiration Control - by the stomata • Stomata opening caused by: • Sunlight/high photosynthesis • Reduced CO2 concentration • Stomata closing caused by: • Water shortage: the hormone abscisic acid (ABA) is produced, forcing closure to prevent dehydration. • Darkness.

28. Transpiration - Control Stomata open - CO2 uptake high, water loss high High pressure in cytoplasm Guard cells turgid

29. Transpiration - Control Stomata closed - CO2 uptake low, water loss low. Low pressure in cytoplasm Guard cells flaccid

30. Abiotic factors affecting transpiration Can you name some? • Light: photosynthesis creates a demand for CO2 • stomata open in response to light to allow gas exchange. • Open stomata allow water to escape. Plants maintain a balance between CO2 uptake and water loss.

31. Abiotic factors affecting transpiration • Heat: • causes water to become vapor in mesophyll & escape through open stomata. • High temps increase transpiration by increasing rate of diffusion of water molecules, increasing rate of evaporation and increasing pressure in the cell.

32. Abiotic factors affecting transpiration • Humidity: • Around the leaf there is a boundary of water vapor. • When conditions are very humid there is little difference between humidity inside or out of the leaf. So transpiration rate is low.

33. Abiotic factors affecting transpiration • Dry/wind: • The concentration gradient of water vapor is greater, so transpiration increases. • Wind blows away the boundary layer of the water vapor next to the leaf so transpiration increases.

34. Adaptations to Reduce Water Loss • What is a Xerophyte? • Xerophytes are plants adapted to arid climates by reducing transpiration. • Where water is at a premium, plants need to adapt to reduce wasting water through transpiration.

35. Life cycle adaptations: • Perennial plants bloom in wet seasons. • Dormant seeds can survive for many years until conditions are ideal for growth. • Complete short life cycles during the brief rainy season.

36. Physical adaptations: • Fewer leaves or stomata. • Rolled leaves or spines. • Stomata in pits with hairs. • Deeper roots to reach water. • Waxy cuticle reduces evaporation.

37. Ocotillo after rain Ocotillo without leaves Fig. 36.16

38. Figure 36.16c Notice the: Reduced leaves Numerous, large spines. Ocotillo leaves

39. Figure 36.16d Oleander leaf cross section Notice the: Thick cuticle Multi-layered epidermal tissue Stomata recessed in cavities called crypts (protect from wind).

40. Prickly Pear Cactus Spines are modified leaf petioles (leaf stems) Thick waxy cuticle on “pads”

41. Metabolic adaptations: • CAM plants (crassulacean acid metabolism). • CO2 is absorbed at night and stored as a C4 compound. • During the day photosynthesis can occur with the stomata closed by using those carbon stores.

42. Active Translocation of Sugars & Amino acids • For a plant to grow and reproduce, the food from photosynthesis (carbohydrates) needs to be transported (translocate) to the tissues that need it. • This is also true of proteins and amino acids. • Active translocation occurs in the phloem (moving food around) • Movement of phloem sap requires energy so it is called active translocation

43. Active Translocation of Sugars & Amino acids • Source – Site of production or storage • Sink – destination or site of use • Sugars • Source: • Green leaves & stems • Storage tissues in seeds • Sinks: • Growing roots and stems • Fruit production or other energy storage • Flowering and reproduction

44. Active Translocation of Sugars & Amino acids • Amino Acids • Source: • Roots or tubers, rhizomes • Storage in germinating seeds • Sinks: • Growing roots and stems • Developing leaves, • Fruits, flowering, and reproduction.