K. Radoglou et Ro. Teskey, CHANGES IN RATES OF PHOTOSYNTHESIS AND RESPIRATION DURING NEEDLE DEVELOPMENT OF LOBLOLLY-PINE, Tree physiology, 17(7), 1997, pp. 485-488
Net photosynthetic rates of developing foliage and one-year-old foliag
e of loblolly pine (Pinus taeda L.) were measured under field conditio
ns. In the subsequent year, net photosynthesis and dark respiration ra
tes of current-year and one-year-old foliage were measured under contr
olled environmental conditions. Loblolly pine foliage grows slowly, re
aching 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, respecti
vely. However, because of high rates of dark respiration during the in
itial growth period, a positive diurnal carbon balance did not occur u
ntil foliage was about a third of final length (40 days after bud burs
t). Two months after bud burst, when foliage was about 55% of final le
ngth, its photosynthetic capacity exceeded that of one-year-old foliag
e. The highest rates of net photosynthesis were achieved when foliage
was more than 90% fully expanded.