plant organisation my work

• water in leaf means

  If there is plenty of water in the leaf, guard cells become turgid, which opens the stomata. This allows carbon dioxide to enter the leaf, but also allows water to escape.
• translocation

  Translocation takes place via phloem tubes. These are made up of lots of phloem cells, which are separated by tiny pores that allow cell sap to pass through.
• transpiration

  When the plant opens its stomata to let in carbon dioxide, water on the surface of the cells of the spongy mesophyll and palisade mesophyll evaporates and diffuses out of the leaf. This process is called transpiration.
• which part of plant is glucose produced in

  leaves (carry out photosynthesis)
• photosynthesis equation

  6CO2 + 6H2O ------> C6H12O6 + 6O2

  carbon dioxide + water --> glucose + oxygen
• rate of transpiration if wind speed increases

  - The wind blows away water vapour as soon as it diffuses out of the leaf.

  - This maintains a strong concentration gradient between the inside and outside of the leaf

  - which increases the rate at which water diffuses out.
• Which structures help to minimise water loss?

  - guard cells that close stomata

  - waxy cutcicle
• what is transpiration

  evaporation of water from plant leaves
• what is translocation

  The movement of sugars through phloem in plants
• Epidermal tissue (plant)

  Covers the plant
• palisade mesophyll


  - Layer of tall, column-shaped mesophyll cells just under the upper epidermis of a leaf

  - photosynthetic
• waxy cutcicle

  helps reduce water loss
• spongy mesophyll


  - loosely packed, irregularly shaped cells with spaces around them ( to allow gases to diffuse in and out)

  - located below the palisade mesophyll
• xylem

  -Nonliving vascular tissue

  - carries water and dissolved minerals from the roots of a plant to its leaves

  - strengthened with lignin

  - transpiration
• phloem

  - Living vascular tissue

  - carries sugar and organic substances throughout a plant

  transport goes in both directions

  - pores in end walls to allow cell sap to flow through

  - translocation
• meristem tissue

  - Found at the growing tips of roots and shoots

  - Able to differentiate into lots of different types of plant cell

  - allows the plant to grow - plant stem cell
• stomata

  the small openings on the undersides of most leaves through which oxygen and carbon dioxide can move
• guard cells

  The two cells that flank the stomatal pore and regulate the opening and closing of the pore.
• upper epidermis is

  -transparent to allow light to get through to palisade layer
• palisade layer has lots of

  chloroplasts
• tissues of leaves are adapted for efficient

  gas exchange
• air spaces in spongy mesophyll


  increase rate of diffusion of gases
• transpiration process:

  - caused by evaporation and diffusion

  - evaporation creates slight shortage at leaves

  - more water runs through xylem vessels to replace it

  - more water being drawn up from roots, so constant transpiration stream in plant
• transpiration rate affected by

  - light intensity

  - temperature

  - air flow

  - humidity
• light intensity transpiration

  -The brighter the light, the greater the transpiration rate

  -because of more photosynthesis
• temperature transpiration

  - warmer, faster transpiration

  - warm means water has more energy to evaporate and diffuse out of stomata
• air flow transpiration

  - better air flow, greater transpiration

  - if air flow is poor then water vapour surrounds leaf and doesnt move

  - high conc of water particles outside of leaf so doesnt diffuse quick
• humidity transpiration

  - air is humid means water already in air

  - smaller difference in concs means diffusion slower

  - diffusion happens fastest on big conc gradients
• guard cells are adapted to

  open and close stomata
• potometer

  - The potometer is filled with water.

  
  

  - A shoot is cut from a woody plant. The end of the shoot is cut under water to ensure that the xylem remains water-filled and prevents air locks.

  
  

  - The shoot is inserted into the rubber tubing at the end of the potometer.

  
  

  - The potometer is raised so that a bubble of air is taken up.

  
  

  - The potometer is lowered into the water. The distance travelled by the air bubble is recorded over a period of time.
• guard cell adaptation details

  1) They have a kidney shape which opens and closes the stomata in a leaf.

  
  

  2) When the plant has lots of water the guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.

  
  

  3) When the plant is short of water, the guard cells lose water and become flaccid. making the stomata close. This helps stop too much water vapour escaping.

  
  

  4) Thin outer walls and thickened inner walls make the opening and closing work.

  
  

  5) They're also sensitive to light and close at night to save water without losing out on photosynthesis.

  
  

  6) You usually find more stomata on the undersides of leaves than on the top.

  The lower surface is shaded and cooler - so less water is lost through the stomata than if they were on the upper surface.

  
  

  7) Guard cells are therefore adapted for gas exchange and controlling water loss within a leaf.