SOURCE TO SINK

• WHAT IS THE SOURCE CELL?

  photosynthesising leaf cell
• WHAT IS THE SINK CELL?

  respiring cell
• WHAT HAPPENS AS THE SOURCE CELL PHOTOSYNTHESISES?

  sucrose lowers the water potential of the source cell, so water enters by osmosis
• WHAT HAPPENS AS WATER ENTERS THE SOURCE CELL BY OSMOSIS?

  increases hydrostatic pressure in source cell
• WHAT HAPPENS AS THE SINK CELL RESPIRES?

  respiring cell is using up sucrose and therefore has a more positive water potential

  -> water leaves sink cell by osmosis
• WHAT HAPPENS AS WATER LEAVES THE SINK CELL BY OSMOSIS?

  decreases hydrostatic pressure in the sink cell
• WHAT HAPPENS AFTER HYDROSTATIC PRESSURE INCREASES IN THE SOURCE CELL AND DECREASES IN THE SINK CELL?

  source cell has higher hydrostatic pressure than the sink cell, therefore the solution is forced towards sink cell via the phloem