These species do very well in nutrient poor soils, but tend not to do well competing against crop plants. This may be a problem, especially for thousands of acres of genetically engineered forest trees that are sprayed with nitrogen to assist in their growth. Leaf fall can return some absorbed nutrients to the soil and nitrogen, phosphorus, potassium, and magnesium move from tree leaves and into twigs and branches before leaf fall and these are used in new growth after the dormant period. Most of the micronutrients are essential mainly because they activate the enzymes. All elements perform another function by contriubting t osomotic potentials, and thus aiding biuldup of the turgor pressure necessary to maintain form, speed growth, and allow certain pressure dependent movements.
Plants have characteristic deficiency symptoms.
Symptoms of deficiency also point to function of the element in the plant. Nitrogen Soils are more deficient in nitrogen than any other nutrient, although phosphorus runs a close second. Nitrogen is a component of amino acids, therfore, lack of nitrogen can stunt the growth of a plant. Deficiencies in nitrogen include chlorosis which results in a yellowing or tan leaf which may fall off the tree. Tomatoes and corn may exhibit a purplish coloration in the stems and petioles.