Hundreds of cells are present in plant leaves. They are coordinated and
likened to an internal molecular compass within each cell. This compass
gives directionality through a biochemical field across the leaf. Called
polarity field, this molecular compass allows cells to coordinate growth and
form the final shape of leaves.
A research team from the John Innes Centre (JIC) tested coordinated polarity
field in the cells of a leaf using Arabidopsis. They used a protein called
BASL to reveal the compass within cells. They found that the BASL protein
was always restricted to the end of the cell closest to the leaf base. The
protein allowed the researchers to see that the cells all have a compass,
pointing in the same direction across the leaf.