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- Title
Seasonal dynamics of nitrogen level and gas exchange in different cohorts of Scots pine needles: a conflict between nitrogen mobilization and photosynthesis?
- Authors
Wyka, T.; Żytkowiak, R.; Oleksyn, J.
- Abstract
Needles of evergreen conifers are not only photosynthetic organs, but they may also serve as storage sites for carbohydrates and nutrients. Since nitrogen is both a component of photosynthetically active molecules and a nutrient stored in the needles and mobilized for shoot regrowth, we searched for evidence of a trade-off between needle N storage and photosynthetic capacity. Using sequential sampling, we tracked seasonal patterns in needle structure, nitrogen ( N) and carbohydrate concentration, and gas exchange in needles of all age classes (current-year, 1- and 2-year-old) present on Pinus sylvestris trees. In both 1- and 2-year-old needles, N increased slightly in the spring, fell subsequently after the onset of shoot growth, followed by replenishment in 1-year-old and further decline until abscission in 2-year-old needles. However, only 2-year-old needles showed a positive correlation between N and photosynthesis, consistent with their overall lower N level that indicated a tighter N budget. The 2-year-old needles had a higher leaf mass per area and lower photosynthesis in comparison with 1-year-old needles. They also had a lower photosynthetic nitrogen use efficiency, which suggests that in addition to N withdrawal, structural change and biochemical modifications might have contributed to photosynthetic decline in the final year of needle life. Thus, whereas seasonal N mobilization observed in 1-year-old needles did not seem to interfere with photosynthetic potential, resorption of N could have contributed to gradual photosynthetic decline in 2-year-old needles.
- Subjects
NITROGEN; PINE needles; NEEDLES (Botany); PHOTOSYNTHESIS; TREES
- Publication
European Journal of Forest Research, 2016, Vol 135, Issue 3, p483
- ISSN
1612-4669
- Publication type
Article
- DOI
10.1007/s10342-016-0947-x