Abstract:
The objective of this study was to determine the effect of age
on rates of transpiration by Douglas-fir seedlings. Seeds were
collected from a xeric site (Goldendale, Washington) and a mesic
site (Forks, Washington). The seedlings were grown in a cold frame
and in a growth chamber for periods of two, four, eight, and sixteen
weeks.
Although much interaction occurred between age, seed source,
and growing condition, significant differences were delineated for
each of the three variables. For both the Forks and Goldendale
seedlings, the transpiration rates were not found to decrease significantly
with increasing age. At a given age, four, eight, or sixteen
weeks, the Forks seedlings grown in the cold frame, in general, had
the highest rates of transpiration.
The effect of seed source was found to be significant when the seedlings were grown in the cold frame. Under these conditions the
seedlings from Forks, Washington, had a significantly higher rate
than the seedlings from Goldendale, Washington.
The effect of conditioning on transpiration resulted in the
seedlings grown in a cold frame having a significantly higher rate
than those grown in a growth chamber.
