A1.1 Water - written task
Water is the solvent in which all the cellular reactions of living organisms take place. Plants also need water for transport and as a source of hydrogen for photosynthesis. The loss of water from the leaves of a plant, transpiration, allows the uptake of water from soil through roots to the leaves.
This structured extension question has a particular focus on the concept of water and its polarity. It uses the "explain" command term.
Explain answers are different from describe because these answers must include the reasons why something happens or the causes of a property.
Answers to a ‘describe question’ only require details about the subject of the question.
Each rice plant in cultivation in India, needs between 800 and 5000 litres of water to produce 1Kg of grain.
Luckily the processes that transport water through a plant are passive and avoid excessive use of energy by the plant.
More of the energy from photosynthesis can be used to grow the rice grains.
There is an unequal sharing of electrons in the covalent bonds between hydrogen and oxygen in water molecules H2O.
Explain how this is important in the movement of water from the roots to leaves of a flowering plant like rice.
(5 marks)
The response must link unequal sharing of electrons with polarity and polarity with tension in the xylem water column.
A diagram could be useful in the response and relevent annotations would gain marks.
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