Unit8

• xylem- transport of water and mineral ions, and support
• phloem- transport of sucrose and amino acids
• vascular bundle- consists of xylem and phloem
• label phloem and xylem of vascular bundle

  A) xylem

  B) vascular bundle

  C) phloem

  D) phloem

  E) xylem

  F) vascular bundle

  G) root hair

  H) phloem

  I) xylem

  
• xylem vessels-

  • thick walls with lignin
  • no cell contents
  • cells joined end to end with no cross walls to form a long continuous tube
• label root hair

  A) cell membrane

  B) cell wall

  C) vacoule

  D) root hair

  E) cytoplasm

  F) nucleas

  
• root hair cell -root cortex cells -xylem -leaf mesophyll cells

  A) root hair cells
• investigate using a suitable stain

  put the plant's roots in water mixed with dye. As the plant absorbs water, the dye will travel through the plant, showing the water's path. Then, you can look at the plant to see where the dye went, showing how water moves through it.
• transpiration- the loss of water vapor from leaves
• water evaporates from the surface area of the mesophyll cells into air spaces and then diffuses out of the leaves through the stomata as water vapor
• limiting factors of transpiration-

  • wind speed
  • temperature
  • humidity
• Humidity Humidity is the concentration of water vapour in the atmosphere. During high humidity transpiration is less. Because the diffusion gradient for water vapors will be less
• Temperature: with increase of temperature the rate of transpiration also increases. Transpiration cools down the plant body. The evaporated water takes away heat energy from the plant and reduces the temperature of the plant. Usually temperature is increased with light intensity. In light intensity more stomata will be open to allow gaseous exchange for photosynthesis. At this condition the chances for transpiration is higher
• Wind speed: wind removes the layers of water vapour from the stomatal surface. So more water vapor is allowed to diffuse out from the plants. Transpiration rate increases with increase of wind speed.
• Water is pulled upward in the xylem through a process called transpiration pull. As water evaporates from the leaves, it creates a negative pressure, drawing water up from the roots. Cohesion between water molecules maintains a continuous column of water in the xylem, facilitating the movement of water from roots to leaves.
• water vapor loss is related to

  • the large internal surface area provided by the interconnecting air spaces between mesophyll cells
  • number of stomata
• wilting occurs due to loss of turgity in leaf
• translocation is the movement of sucrose and amino acids in phloem from source to sink
• source is the place where its produced
• sink is the place where its stored
• a potato act as a sink when leaf transports sucrose. and a source when the new shoot is the sink
• label transpiration in plants

  A) diffusion through stomata

  B) mesophyll cells

  C) xylem

  D) root cortex cells

  E) root hair cells

  F) water in the soil