Biology · Transport in plants
Outline the transport needs of plants and the fact that some mineral ions and organic compounds can be transported within plants dissolved in water.
Draw, label and describe the overall structure of herbaceous dicotyledonous stems, roots and leaves using a light microscope.
Draw the structure of the transport tissues xylem and phloem using the high-power lens of a light microscope.
Explain the process of transpiration.
Describe the adaptations of the leaves of xerophytic plants with the aid of annotated drawings.
Explain how water moves across a leaf through the apoplast and symplast pathways.
Relate the structure of xylem to its functions.
Explain the movement of water up the xylem from root to leaf, including the roles of cohesion–tension and adhesion.
Describe the transport of water from the soil to the root xylem through the apoplast and symplast pathways.
Relate the structure of phloem to its functions.
Explain that assimilates dissolved in water, such as sucrose and amino acids, move through phloem sieve tubes from sources to sinks.
Explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink.
Explain how companion cells transfer assimilates to phloem sieve tubes.
Students often think xylem is only for transport, but actually its lignified walls also provide significant structural support to the plant.
Students often think phloem sap moves only downwards, but actually it can move in any direction, from source to sink, depending on the plant's needs.
Students often think stomata are always open, but actually they close at night or during water stress to conserve water.
Students often think xylem vessel elements are living cells, but actually they are dead at maturity, leaving an empty lumen for water flow.
Students often think water can freely enter the xylem from the cortex, but actually the endodermis with its Casparian strip regulates this movement.
Students often think sieve tube elements are dead like xylem vessels, but actually they are living cells, albeit highly modified with reduced organelles.