a) grow by increasing the number of cells
b) and by cell enlargement (increase in cell size).
c) They often carry on growing continuously
(As previously mentioned under Sensitivity, plants know which way to grow – roots downwards, green shoots upwards – because they are sensitive to gravity. But plants can also direct their growth in response water and light – roots towards moist areas of soil, and green shoots towards the sun.
a) Grow by increase in number of cells
b) Tend to grow to a maximum size then stop (although cells are continuously being replaced)