Is Climate Simulation in Growth Chambers Necessary

WANG 2. M.. JOHXEN K. H. and LECHO~VICZ iM. J. Is climate simulatiori in growth chambers necessary? BIOTRONICS 28, 13-21, 1999. In the expression of their genetic potential as phenotypes, trees respond to environmental cues such as photoperiod, temperature and soil and atmospheric water. However, growth chamber experiments often utilize simple and standard environmental conditions that might not provide these important environmental signals. We conducted a study to compare seedling growth in the field to both a standard growth chamber regime and a growth chamber regime programmed to simulate seasonal and diurnal variation in daylength. light intensity, temperature and relative humidity. Twenty-four open pollinated families of black spruce were grown in a nursery bed for one season while in situ temperature and relative humidity were recorded. The same 24 families were then grown under two growth chamber protocols: standard conditions (16 hour day and 8 hour night at temperatures 20°C and 15°C and 70% and 90% relative humidity, respectively) and climate simulation (programmed variation in diurnal temperature and relative humidity, and daylength). Seedlings from the climate simulation regime were similar to field-grown seedlings with respect to seedling size and dry matter partitioning. Seedlings from the standard growth chamber regime grew larger and allocated more dry matter to the shoots, compared to both other growth regimes. Results clearly indicate that simulating more realistic natural environments in ecophysiological studies can produce results closer to what are observed in the field.