Cone count records for a 28-year period on 80 Douglas fir, 14 grand fir, and 9 western white pine were statistically analyzed with the annual diameter increment to evaluate the relationship between cone and wood production. The width of annual rings was depressed only during the years of cone production, suggesting that carbohydrates used in cone development were supplied from current photosynthesis rather than from stored reserve. The initiation of reproductive buds did not appear to be dependent on the level of carbohydrates in a tree and the role of carbohydrates was probably only that of nutrition during cone development. Maturing cones did not exhibit any inhibitory effect on initiation of new flowering buds. Different species may require a different combination of climatic factors for initiation of flowering buds.

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Partial girdles were applied in August, 1957, to one stem of two double-stemmed, 20-year-old Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). The second stem served as control. A third double-stemmed tree was treated in May, 1958. Cone production responses were obtained on all three girdled stems, averaging 7.4 times that of control stems in 1959, and 1.6 and 2.3 times that of control stems in 1961 and 1962. Cone production responses to treatment, and cone crop variation over several years were correlated with reduced bud failure during the period of new shoot elongation. Total number of buds per shoot was initially similar for paired stems. These relationships indicated a predetermined potential for annual cone production, and that cone crop periodicity is determined by later conditions favorable or unfavorable to continued early bud development. Treatment increased both sugars and starch in shoots sampled 40 days after August girdling, but only starch remained elevated the next spring and throughout the decisive May–June period of reproductive bud development. Other factors indicated food reserves to be related only weakly to reproductive bud survival. Cone production reduced carbohydrate concentration in shoots of all ages, growth and number of new shoots, and number of developed buds per shoot. These factors explain the absence of consecutive cone crops in Douglas fir, and suggest that cone inducing treatments should not be applied in good flowering years. Cone production responses on single-stemmed trees girdled at weekly intervals showed an optimum timing coincident with the onset of flowering, a more variable response up to the time of vegetative bud break, then an adverse effect on cone production when girdled later than 1 week after vegetative bud break.

Nitrogenous substances were analyzed from 6-week-old foliage of 13-year-old Douglas fir, treated at vegetative bud break with 200 to 1600 lb/ac of ammonium or nitrate nitrogen. Increasing rates of nitrate nitrogen elevated seed cone production the next year by 2 to 7 times, whereas ammonium nitrogen produced no responses. Total nitrogen increases and shoot growth were similar from the two forms of nitrogen. Increases in total free amino acids with increasing rates of nitrate treatment were double those from ammonium, but size of the free amino acid pool appeared unrelated to seed cone production. Amino acid patterns, and traces of several guanidino compounds, from ammonium treatments did not vary appreciably from those of the untreated control. Most of the increase in total nitrogen from ammonium treatment was incorporated as protein, but electrophoretic patterns did not vary qualitatively with the form of nitrogen supplied. Large accumulations of basic amino acids, notably arginine, and guanidino substances resulted from nitrate treatment. This arginine-type metabolism appeared quantitatively associated with seed cone production.