What you will learn in How water climbs and sugar travels

1. 1. Water potential

   One quantity that predicts which way water moves between any two places — cell, soil, root or air.

2. 2. The 10-metre problem

   Build a plant that lifts water by suction, watch it fail, and find what a tall tree does instead.

3. 3. The cost of being open

   Stomata let carbon dioxide in and water out through the same pore. Look for a setting that avoids the cost.

4. 4. Moving sugar

   Sources load sugar, sinks unload it, and the phloem carries it from high pressure to low in whichever direction that is.

5. 5. What comes out of the soil

   Which leaves yellow first tells you which kind of nutrient is short — and only legumes have bacteria fixing nitrogen for them.