auxin
plant hormone or substance that promotes or regulates the growth and development of plants. Produced at sites where cells are dividing. primarily in the shoot tips. Auxin-like compounds may be synthetically produced.
available water
water remaining in the soil after gravitational water has drained and before the permanent wilting point has been reached. (compare to field capacity. gravitational water. permanent wilting point. and saturation point).
axial transport
movement of water. minerals. or photosynthates longitudinally within a tree.