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Plants Cell

cell wall. cytoplasm. vacuole. cell membrane. Plants Cell. freely permeable so it lets most of molecules to go through osmosis does not occur cell membrane beneath cell wall selectively permeable. cell wall. net water movement into the cell by osmosis.

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Plants Cell

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  1. cell wall cytoplasm vacuole cell membrane Plants Cell

  2. freely permeable so it lets most of molecules to go through • osmosis does not occur cell membrane • beneath cell wall • selectively permeable cell wall

  3. net water movement into the cell by osmosis plant cell contains solutes  water potential lower than pure water vacuole and cytoplasm swells Water Relations of Plant - Turgor plant cell put in distilled water

  4. cytoplasm is pushed against cell wall turgor hydrostatic pressuredevelops inside the cell turgor is present because: cell wall is rigid and strong, cell bursting is prevented

  5. tendency of the cell to give out water increases water potential increases Turgor occur (cell cannot take in any water) the cell is turgid When water potential of cell = water potential of water

  6. net water movement out of the cell by osmosis flaccid vacuole and cytoplasm shrink cytoplasm is torn away from cell wall Water Relations of Plant - Plasmolysis plant cell in concentrated solution The whole phenomenon is called plasmolysis and cell is plasmolysed

  7. cell membrane separated from cell wall cell wall vacuole enlarged vacuole very small cytoplasm solution here is the same as the external solution Turgidity of Plant Cells plasmolysed cell (in hypertonic sol) turgid cell (in hypotonic sol.)

  8. Cells in Different Solutions Solution Concentration hypotonic hypertonic animal cells (e.g. RBC) haemolysis shrink plasmolysis (cell is flaccid) plant cells turgid

  9. Investigation 11.2 To Investigate the Effects of Sucrose Solution and Tap Water on Epidermal Cells of Red Onion Scale Leaf or Rhoeo Discolor Leaf

  10. fleshy scale leaf of red onion bulb filter paper forceps epidermis What do you observe when the epidermal strip is placed in the concentrated sucrose solution ? Ans:The coloured cytoplasm shrinks.

  11. fleshy scale leaf of red onion bulb filter paper forceps epidermis Explain your observation. Ans:When the piece of epidermis is placed in concentrated solution, cells lose water by osmosis as the cells have a higher water potential than the sugar solution.

  12. fleshy scale leaf of red onion bulb filter paper forceps epidermis What has happened to the cells in tap water ? Ans:The coloured cytoplasm swells and cells become turgid.

  13. fleshy scale leaf of red onion bulb filter paper forceps epidermis Explain your answer. Ans:When the piece of epidermis is placed in tap water, cells gain water by osmosis as the surrounding tap water has a higher water potential than the cells.

  14. Investigation 11.3 Effects of Concentrated Sucrose Solution and Tap Water on Raw Potato Strips

  15. petri dish 20% surcose solution water raw potato strips A B What has happened to the potato strips ? Ans:Potato strip A increases in both weight and length while potato strip B decreases in both weight and length.

  16. petri dish 20% surcose solution water raw potato strips A B Explain your answer. Ans:For potato strip A, it gains water by osmosis so both of its weight and length increase but for potato strip B, it loses water by osmosis so its weight and length decrease.

  17. Transpiration • an evaporation of water in form of water vapour from the surface of plant to atmosphere • it mainly takes place in leaves where there are some openings called stomata

  18. more water loses from the lower surface of the leaf than the upper one as more stomata present on the lower surface • it also happens in lenticels and cuticle

  19. Transpiration in Leaves • a thin film of moisture is covered with each mesophyll cell • the moisture evaporates from mesophyll cells into intercellular spaces and diffuses out of stomata into atmosphere

  20. water potential of cells losing water decreases so they draw water from deeper cells in the leaf by osmosis. This in turn, draws water in xylem vessels into leaf to replace the loss

  21. Investigation 11.4 Experiment to Show that Water is Given Off During Transpiration

  22. polythene bag A B What do you observe in the polythene bags ? Ans:The one enclosing plant A becomes misty while nothing can be noticed in the one enclosing plant B.

  23. polythene bag A B How can you show that it is water ? Ans:We can use anhydrous cobalt chloride paper to test it. It will turn the paper from blue to pink or we can use anhydrous copper sulphate. Water will turn it from white to blue.

  24. polythene bag A B What conclusions can you draw from the results ? Ans:We can conclude that a leafy shoot gives off water during transpiration.

  25. Investigation 11.5 To Measure the Rate of Transpiration by Using a Simple Potometer

  26. graduated capillary tube leafy shoot air/water meniscus tap reservoir What are the environmental conditions under which transpiration occurs quickly ? Ans:It is under dry, warm and windy conditions.

  27. graduated capillary tube leafy shoot air/water meniscus tap reservoir Does this apparatus give you an accurate measurement of the rate of transpiration ? Ans:No. It is because it only measures the rate of water uptake by the leafy shoot … Ans:In addition, it is too small to fit the whole root system and this may affect the rate of water uptake.

  28. graduated capillary tube leafy shoot air/water meniscus tap reservoir Sometimes you may introduce an air bubble into the capillary tube. State the advantage of this method. Ans:Movement of the air bubble is easier to observe than that of air/water meniscus.

  29. graduated capillary tube leafy shoot air/water meniscus tap reservoir Sometimes you may introduce an air bubble into the capillary tube. State the disadvantage of this method. Ans:Friction between the capillary wall and the bubble may affect the movement of bubble.

  30. Environmental Factors Affecting the Rate of Transpiration There are five environmental factors which affect the rate of transpiration. They are: (I) Light Intensity (II) Temperature (III) Humidity (IV) Wind Speed (V) Water Supply

  31. Light Intensity • stomata open in light, so plants can get enough carbon dioxide from atmosphere for carrying out photosynthesis • light will increase temperature so increases the rate of transpiration

  32. rate of evaporation of water from mesophyll cells temperature relative humidity of air outside leaf rate of diffusion of water vapour from intercellular space in leaf to outside Temperature

  33. humidity outside rate of transpiration it makes the diffusion gradient of water vapour from moist intercellular space of a leaf to the external atmosphere steeper  Humidity

  34. water vapour around the leaf sweeps away soil dries, plant wilts and stomata close transpiration rate transpiration rate Wind Speed & Water Supply wind blows lack of water INCREASES DECREASES

  35. Stomata • stomata are pores in the epidermis which gaseous exchange takes place during photosynthesis (or respiration) • find mainly in lower epidermis of dicotyledonous leaves and stems

  36. guard cell stoma Guard Cells • each stomata is surrounded by two guard cells which possess chloroplasts • its inner wall is thicker than outer wall • it is kidney-shaped

  37. Distribution of Stomata in Leaves • normal plants • mainly on the lower surface of leaves • floating plants • mainly on the upper surface • leaves may also have air sacs to keep them afloat so they can carry out gaseous exchange

  38. submerged aquatic plants • no stomata (not required since gaseous exchange can be carried out by diffusion though the leave surface) • no cuticle (the primary function of cuticle is to prevent excess water transpiration which is not present in aquatic plants)

  39. Investigation 11.6 Experiment to Investigate Stomatal Distribution in a Leaf by Using Cobalt Chloride Paper

  40. cobalt chloride paper sellotape Obtain a potted plant. Using sellotape stick a small square of anhydrous cobalt chloride paper onto each surface of a leaf of the plant. Record the time taken for the cobalt chloride paper on each surface of the leaf to turn pink.

  41. cobalt chloride paper sellotape Which piece of cobalt chloride paper turns pink first? Ans:The piece of cobalt chloride paper attached to the lower epidermis of the leaf turns pink first.

  42. cobalt chloride paper sellotape Explain your answer. Ans:It is because more stomata are present in the lower epidermis.

  43. cobalt chloride paper sellotape Why is it important to handle cobalt chloride paper with forceps? Ans:It is because there is moisture on human fingers so the paper may turn pink before sticking onto the surfaces of leaves.

  44. Investigation 11.7 To Observe the Release of Air Bubbles from Leaves placed in Hot Water

  45. forceps hot water leaf Which surface has more air bubbles coming off? Ans:There are more air bubbles appear on the lower surface of the leaf.

  46. forceps hot water leaf Where does the air come from? Ans:It is in the air spaces between the mesophyll cells in leaf which expands on heating and passes out through stomata of the leaf.

  47. forceps hot water leaf What does the result show? Ans:The result shows that more stomata are present on the lower epidermis of the leaf.

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