GROWTH REGULATOR CHANGES IN RELATION TO GROWTH AND DEVELOPMENT OF PINUS RESINOSA AIT.

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Abstract
The occurrence of growth regulators and nucleic acids in buds of red pine trees has been investigated in relation to seasonal change, position of the bud in the crown, and age of the tree. The regulators were extracted, separated by chromatography, and assayed by an Avena straight-growth test. Three growth promoters and an inhibitor were found in the buds on all occasions. All of them affected the growth of hypocotyls of red pine seedlings as well as Avena inter-nodes, and none gave an indole reaction. The regulators varied in concentration in relation to season, age, and bud position. The individual growth promoters varied independently, one of them, designated as P1, being more variable than the others. Changes in the inhibitor were frequently, but not invariably, reciprocal to those of P1. There is evidence that individual growth promoters may be concerned with separate aspects of growth. The balance between P1 and the inhibitor was related to extension growth, with the notable exception that a balance favorable to growth reappeared in September, when no growth occurs. RNA concentration declines during the summer and a deficiency of this nucleic acid could be implicated in the cessation of growth.Treatment with ammonium nitrate fertilizer caused a shift from male to female cone production and a localized increase in the number of shoots that developed in the following year. These effects were accompanied by changes in concentration of growth promoters in the buds.