Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 5. Changes in free arginine and Sakaguchi-reactive compounds during callus growth and in germinating seedlings of similar genetic origin

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Abstract
In friable callus, grown on a defined medium with arginine, and in jack pine seedlings, from which callus was derived, at least 18 Sakaguchi-reactive compounds and 2 N-phosphoryl derivatives were detected. When final size of callus was reached, the N in these substances contributed 0.1% to the total gain in dry weight and less than 0.6% to the gain in N. This was equivalent to a loss of 3-7% of the arginine N in the medium. For each callus, the total content of Sakaguchi-reactive compounds increased as the relative growth rates for weight and volume decreased. The increase was more pronounced when daughter cells adhered to clumps than at earlier stages when cells separated from one another. On a unit weight basis and as the cultures reached final size, the total Sakaguchi-reactive substances fell as .gamma.-guanidinobutyric acid increasingly dominated the guanidine fraction. Exogenously supplied .gamma.-guanidinobutyric acid caused a decrease in the final size of the cultured calluses when compared with calluses supplied with arginine. Levels of some of the remaining unidentified guanidines correlated positively with growth rates of calluses. By contrast, during the first 10 days of seedling growth Sakaguchi-reactive compounds contributed 12% of the net gain in N. The sequence of dominance of guanidines during growth was similar in both callus types and in seedlings, although some differences were noted.

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