Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 2. The quantitative analysis of the growth of callus from hypocotyls and radicles

Abstract

Jack pine (Pinus banksiana Lamb.) calluses from hypocotyls and radicles of 5-day-old seedlings were established when the yield of callus from the donor was greatest compared with other stages of germination. Effects of macroelements, organic nitrogen sources, growth regulators, temperature, light, and carbon dioxide on the fresh and dry weights of callus indicated that the medium formulated was optimal. Although tissues assimilated exogenous sources of N, they also depended upon the food reserves that were mobilized during germination as the density (dry weight per cubic centimetre) of calluses gradually fell.Initially, the proliferation and release of cells from their neighbors was mainly on the outer surface of tissue. Eventually all cells appeared to divide to yield a friable, green callus with cell clumps that were easily dissociated from one another. Some clumps, especially those below the surface and near vascular tissues, were filamentous and exhibited polarity resembling the early stages of pine embryogeny.The growth form of hypocotyl callus was autocatalytic, whereas radicle callus was exponential for both dry weight and volume. Final size was greater in hypocotyl callus. In both systems, the relative growth rates of weight and volume correlated negatively but significantly to water intake. Average parameters of growth rates were calculated using Richards's comprehensive growth function.