plant transport

• Xylem is responsible for transporting water and minerals from the roots to the rest of the plant.
• transpiration is the loss of water by diffusion via the stomata
• translocation is the movement of sugars and amino acids from the leaves to the rest of the plant
• single celled organisms have a large SA:Vol ratio, while multicellular organisms have a small SA:Vol ratio
• multi cellular organisms have a low SA:Vol ratio, which means diffusion is too slow to move substances obtained in a multi cellular organism. they all have a transport system.
• Transpiration stream – the movement of water up xylem vessels from roots to leaves.(MP1) Water moves by osmosis • (MP2) from a dilute solution to a more concentrated solution • (MP3) from the soil into root hair cells. • (MP4) Water moves by osmosis through the root and into the xylem. Then travels up the xylem in the transpiration stream. • (MP5) Water enters the leaves and moves out of the xylem. Water evaporates to form water vapour in the air spaces by stomata.
• transpiration is important for plants because it draws water up the plant to be used for photosynthesis (MP1) and to prevent leaves wilting (MP2). In addition, it supplies mineral ions to cells in the leaves (MP3) and the evaporation of water out of stomata causes a cooling effect, preventing leaves from overheating (MP4).
• The rate of transpiration depends on factors such as temperature, light intensity, humidity, wind speed and leaf surface area (MP5)
• the rate of transpiration increases with increasing temperatures due to increased rates of evaporation (MP6)
• increasing light intensity will increase the rate of transpiration as there are more carbon dioxide molecules available for photosynthesis (MP7)
• the rate of transpiration decreases when there are fewer stomata open or if the stomata close completely (MP7)
• decrease in relative humidity leads to an increase in the rate of transpiration as the concentration gradient between inside and outside the leaf becomes greater (MP8)
• the rate of transpiration decreases with increasing humidity (MP9)
• root hair cells:

  long projection- larger SA, increases rate of osmosis.

  lots of mitochondria- more aerobic resp., more ATP, more energy.

  one cells thick - short osmosis distance
• To set up a bubble petometer, cut the leafy stem under water at an angle.
• Insert the shoot into the capillary tubing that is full of water and placed in a beaker of water.
• Ensure the seal between the shoot and the capillary tubing/bung is air tight.
• Lift the capillary tubing out of the beaker of water to introduce an air bubble.
• Place the capillary tubing back into the beaker of water.
• Dry the leaves of the shoot to ensure valid results.
• Measure the distance the bubble moves using a ruler in a set period of time.
• Reset the position of the air bubble using the reservoir and repeat.
• aphids track radioactivity by secreting enzymes to prevent the phloem from forming a 'scab'
• radioactive carbon is converted to sucrose in the leaves and moved along the stem
• aphids can identify much more easily where the phloem is found
• calculating a rate of water loss:

  coat one leaf with vaseline on the underside, one with vaseline on the top, one with vaseline on bith sides, and one leaf left normal
• transpiration rate = mass lost / surface area x time taken
• % change in mass = initial-final/initial x 100
• water loss = mass/SA
• more stomata are found on the underside of the leaf
• magnesium and nitrate are two minerals needed for planta