Springtime resumption of photosynthesis in balsam fir (Abies balsamea)
G. K. Goodine (1, 2, 3), M. B. Lavigne (1) and M. J. Krasowski (2)
1. Natural Resources Canada, Canadian Forest Service - Atlantic Forestry Centre, P.O. Box 4000, Fredericton, NB E3B 5P7, Canada / 2. Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, NB E3B 6A2, Canada / 3. Corresponding author () / Received April 20, 2007; accepted December 5, 2007; published online May 1, 2008
Summary
Photosynthesis in balsam fir (Abies balsamea (L.) Mill.) was measured in the field at two locations in New Brunswick, Canada from late winter to late spring in 2004 and
2005. No photosynthesis was detectable while the soil remained below 0 °C throughout the rooting zone. In both years, photosynthesis
began once soil temperature rose to 0 °C. In potted seedlings in growth chambers, there was no photosynthesis at an air temperature
of 10 °C if the pots were frozen. These findings suggest that, once air temperatures permit photosynthesis, it is the availability
of unfrozen soil water that triggers the onset of photosynthesis. In the field, full recovery of photosynthetic capacity following
the onset of soil thaw was dependent on air temperature and took 5 weeks in 2005, but 10 weeks in 2004. There were two substantial
frost events during the recovery period in 2004 that may explain the extended recovery period. In 2005, recovery was complete
after the accumulation of 200 growing degree days above 0 °C after the start of soil thaw.
Keywords:
environmental controls, frost, isothermal soil temperature, maximum rate of carboxylation, maximum rate of electron transport,
photosynthetic capacity, soil temperature, soil thaw, stomatal limitation, water availability.
