1. Xylem tissue
1.1. Xylem vessels
1.1.1. Made from dead cells aligned end-to-end to form a continuous column
1.1.1.1. To transport water and mineral ions as an unbroken column of water
1.1.2. No cell contents or end walls between the individual xylem elements
1.1.2.1. Nothing to impede flow of water
1.1.3. Narrow tubes with a diamter between 0.01mm and 0.2mm
1.1.3.1. So the water column does not break easily and capillary action occurs
1.1.4. Lignified cell walls
1.1.4.1. Strengthens wall to prevent cell walls from collapsing under tension, waterproofs cell and allows adehsion to increas capillary action
1.1.4.2. As plants get older their cell walls become more lignified going from annular to spiral to pitted
1.1.4.2.1. Allows xylem to stretch as plant grows and enables stem to bend
1.1.5. Pits (non lignified regions)
1.1.5.1. Allow sideways movement of water from one xylem vessle to another or to living cells (parenchyma)
1.2. Sclerenchyma
1.2.1. thickened lignified cell walls to provide support
1.3. Parenchyma
1.3.1. Packing tissue and storage
2. Phloem tissue
2.1. Sieve tube elements
2.1.1. Thin layer of cytoplasm and few organelles at the edge of cell
2.1.1.1. Ease flow of sap
2.1.2. Elongated cells arranged end-to-end
2.1.2.1. To transport assimilates long distances around plant
2.1.3. Many plasmodesmata
2.1.3.1. Allows movement of substances between sieve tube element and companion cell
2.1.4. Sieve plate
2.1.4.1. Allows flow of sap between cells aranged end-to-end
2.2. Companion cells
2.2.1. Many mitochondria
2.2.1.1. To produce ATP for active loading of sucrose into sieve tube elements
2.2.2. Many plasmodesmata
2.2.2.1. Allows movement of substances between sieve tube element and companion cell
2.2.3. Nucleus
2.2.3.1. Controls gene expression for both companion cell and sieve tube element
2.2.4. Proton pump and co-transporter
2.2.4.1. Active loading of sucrose
2.2.5. Many ribosomes on RER
2.2.5.1. Synthesis of transport proteins
3. Plants require a mass transport system
3.1. For water and mineral ions
3.1.1. Must be transported from the roots to the leaves
3.1.2. Trasported in the xylem
3.2. For the products of photosynthesis
3.2.1. Must be transported from a source (e.g. leaves) to sinks (e.g. growing part of the plant)
3.2.2. Transported in the phloem
3.3. Not for oxygen and carbon dioxide
3.3.1. Demand is met by diffusion
4. Organisation of vascular tissue in dicotyledonous plants
4.1. Leaves
4.1.1. Central vein (midrib) branches into other veins forming a branching network
4.2. Roots
4.2.1. Epidermis
4.2.1.1. Outer layer containing root hair cells for the absorption of mineral ions
4.2.2. Cortex
4.2.2.1. Lies beneath the epidermis and contains unspecialised cells which play a role in storage
4.2.3. Endodermis
4.2.3.1. Surrounds vascular bundle and plays a key role in the transport of water into the xylem
4.2.4. Pericycle
4.2.4.1. Meristematic tissue which lies jest inside the endodermal layer
4.2.5. Xylem
4.2.5.1. Forms an X at the centre of the vascular bundle
4.2.6. Phloem
4.2.6.1. Lie between the arms of the X
4.2.7. Cambium
4.2.7.1. Meristematic tissue which lies between the xylem and the phloem
4.3. Stem
4.3.1. Vascular bundles are arranged in a ring towards the outside of the stem
4.3.2. Xylem are closer to the centre of the stem
4.3.3. Phloem are closer to the outside of the cell
4.3.4. Cambium is between phloem and xylem
4.3.5. Sclerenchyma next to phloem
4.3.6. Stem dissection
4.3.6.1. Transverse section or longitudinal section
4.3.6.2. Differential stain (toluidine) is used
4.3.6.2.1. Non-lignified tissue is stained pink/purple
4.3.6.2.2. Liginified tissue is stained green/blue