xylem bio

(k) Describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue.
Parts of Plants:
Roots  Structural support & transports by taking in water & nutrients, process of diffusion
Root Hairs – Increase S/A, are extension of epidermal cells
Stems in vascular tissue, which is made of xylem & phloem.
Xylem – transports water & dissolved minerals
Long tubes made up of series of cells.
From roots upwards to leaves; useable for tree with maximum height.
Phloem – transport sucrose, produced in photosynthetic tissue to other regions of plant, as well as hormones & any other organic material made by plan.
Role begins at leaves
Transports ‘sap’ to rest of plant
Phloem cells linked by sieve plates for continuity.
Sugar moved using turgor pressure
How Materials Move in Vascular Tissue:
Xylem:
Water absorbed by root hairs  moves through the cortex into xylem (small xylem vessels) in vascular tissue  (transported throughout plant) into mesophyll cells in leaf
Water absorbed by root hairs (via osmosis & root pressure)  Move through cortex into xylem (small xylem vessels) via symplastic loading (movement through cell) & apoplastic loading (movement through cell wall)  Water movement up xylem by capillarity  Stomata controls transpiration allowing water to leave xylem into leaf  water in leaves
Mesophyll cells – cells in leaves specialised for photosynthesis.
Walls are moist – air spaces around them contain water.
Gases enter & leave leaf through stomata – when sun shines, stomata opens & gases DIFFUSE in & out of leaf.
- Diffusion – high to low concentration
Water evaporates from wall of mesophyll cells to replace that lost from air spaces to ensure walls are moist.
Water lost by plant (by transpiration) moves through stomata.
Transpiration Stream – column of water which is sucked up the stem by the evaporative pull of transpiration, causing an upward movement in xylem. Is the mechanism