Plant transport

• Translocation is essentially the movement of sucrose and amino acids in phloem from regions of production to regions of storage or regions of utilisation in respiration or growth.
• Source is the part of the plant from which sucrose and amino acids are being translocated. Sink is the location their headed / translocated to.
• In summer the leaves photosynthesize and produce sucrose. That sucrose is then translocated to the sink (the tubers)>
• In winter the starch is stored in the tubers.
• In spring the sucrose is then sent to the new shoots, where the new shoots use them as they grow. In this case the tubers are the source and the shoots are the sink.
• The xylem transports water and minerals whereas the phloem transports organic nutrients which the plant has made.
• Fill in the blanks of this diagram.

  A) epidermis

  B) cortex

  C) xylem

  D) phloem

  E) xylem

  F) phloem

  
• Where is the vascular bundle in the leaf. If that is not the vascular bundle type "not here", if it is type "here".

  A) Here

  B) not here

  C) not here

  D) not here

  
• Root hair cells absorb water by means of osmosis. Since water is in a higher concentration in the soil it goes down the concentration gradient into the root hair cell.
• Fill in the blanks of this diagram:

  A) root hair cell

  B) root cortex cell

  C) xylem vessels

  
• The pathway by water through root stem and leaf is:

  root hair cells -> root cortex cells -> xylem vessels -> mesophyll cells
• Transpiration is the evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata.
• Evaporation:

  -> the cells inside the leaf are covered with a thin film of moisture

  -> some of it evaporates from this cell, and this water vapour diffuses out of the leaf through the stomata

  -> water from the xylem vessels in the leaf will travel to the cells by osmosis to replace it.
• Humidity decreases the transpiration rate as the rate of diffusion of water decreases as the concentration gradient outwards becomes less steep.
• Temperature increases the transpiration rate as the rate of evaporation increases.
• Light increases the transpiration rate as more stomata are open for photosynthesis, allowing for more gas exchange.
• Wind increases the transpiration rate as it carries away water vapour from the leaf which then decreases humidity outside of the leaf.
• Xylem is a system is long hollow tubes (continuous tubular structures) which have walls impregnated with lignin that strengthens them, allowing them to withstand the very low pressure they have to. Xylem cells die before they are functional. Xylem sap moves from roots to stem to leaves without ANY energy being spent by the plants.
• Xylem cells have to be dead because their cell walls must be lignified and their inner components must be lost. This will only be possible if the cells are dead.
• Adhesion is when water is attracted to the cellulose in the cell wall, and so when water evaporates from the surface, adhesion causes water to be drawn through the cell wall from the nearest available supply.
• Transpiration pull is when low pressure is used to generate a pulling force down the stem through the roots, it is strong enough to move water upwards against the force of gravity to the top of the plant.
• Cohesion depends on the cohesion that exists between water molecules, as even though water is liquid it can transmit pulling forces.
• Fill in the blanks of this diagram

  A) adhesion

  B) cohesion

  
• Wilting happens when rate of transpiration > rate of water uptake because cells lose turgor pressure and become flaccid.
• Fill in the blanks of this diagram of the factors that affect the rate of transpiration:

  A) shoot

  B) reservoir

  C) rubber tubing

  D) tap

  E) meniscus

  F) capillary