© 1997 Heron Publishing—Victoria, Canada
Changes in rates of photosynthesis and respiration during needle development of loblolly pine
Kalliopi Radoglou (1, 2) and Robert O. Teskey (1, 3)
1. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602, USA / 2. Forest Research Institute, Vassilika 57006, Thessaloniki, Greece / 3. Author to whom correspondence should be addressed / Received September 24, 1996
Summary
Net photosynthetic rates of developing foliage and one-year-old foliage of loblolly pine (Pinus taeda L.) were measured under field conditions. In the subsequent year, net photosynthesis and dark respiration rates of current-year
and one-year-old foliage were measured under controlled environmental conditions. Loblolly pine foliage grows slowly, reaching
its final size 3.5 to 4 months after bud burst. Positive rates of net photosynthesis were recorded when the foliage was 13
and 18% of final length, in the controlled-environment and field study, respectively. However, because of high rates of dark
respiration during the initial growth period, a positive diurnal carbon balance did not occur until foliage was about a third
of final length (40 days after bud burst). Two months after bud burst, when foliage was about 55% of final length, its photosynthetic
capacity exceeded that of one-year-old foliage. The highest rates of net photosynthesis were achieved when foliage was more
than 90% fully expanded.
Keywords:
bud burst, carbon balance, dark respiration, foliage development, leaf growth, net photosynthesis, photosynthetic capacity,
Pinus taeda, respiration rate.
