Sexual expression in container-grown jack pine seedlings.

We assessed the effects of nitrogen, drought and gibberellin A(4/7) on sexual expression of 2- and 3-year-old jack pine (Pinus banksiana L.) seedlings grown in either a 1/3 peat/sand mix or a 3/1 peat/perlite mix. The seedlings were either watered daily (well-watered treatment) or droughted by withholding water from July 13 to August 24 (drought treatment). Half of the plants in each irrigation treatment were sprayed with 200 mg l(-1)gibberellin A(4/7) at weekly intervals from June 28 to August 24; the remaining plants were not sprayed. Each gibberellin treatment was split into three subplots, and each subplot was supplied with nitrogen in the nutrient solution at 3, 100 or 300 mg l(-1) from June 27 to September 11. The drought treatment increased pollen strobilus production, whereas seed strobilus production was higher in well-watered trees than in drought-treated trees in the first year after treatment, but not in the subsequent year. Gibberellin A(4/7) promoted seed strobilus production but not pollen strobilus production in the first year after treatment but had no effect in the second year. Among the nitrogen treatments, the largest proportion of trees bearing pollen strobili was in the 3 mg l(-1) N treatment. Nitrogen supply did not affect seed strobilus production in the first year after treatment, but in the following year, the proportion of trees with seed strobili was higher in the 3 mg l(-1) N treatment than in the 100 and 300 mg l(-1) N treatments. Growing medium had no detectable effect on pollen strobilus production, but in the year following treatment, more trees produced seed strobili in peat/sand than in peat/perlite.

Effects of environmental changes on sugars, tannins, and organized growth in cell suspension cultures of white spruce.

Callus from hypocotyls of white spruce (Picea glauca [Moench] Voss) was grown on agar under defined conditions with high levels of calcium nitrate. Transfer of callus to liquid suspension cultures and maintenance of suspensions either under a regime of constant temperature and light or under alternating conditions similar to those of a late spring day, affected the content of free sugars, tannins, and aldehydes. Under the alternating conditions the levels of these substances increased greatly compared to those under the constant environment. By contrast, vascularization of cell clumps, which was comparable to the differentiation of hypocotyls in seedlings, was obtained only under constant conditions. Cells at the centre of the clumps developed secondary wall thickenings and bordered pits, and were surrounded by cambial-like initials.