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Acquisition and within‐plant allocation of 13 C and 15 N in CO 2 ‐enriched Quercus robur plants
Author(s) -
Vivin Philippe,
Martin Francis,
Guehl JeanMarc
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb00678.x
Subject(s) - quercus robur , botany , biology
We assessed the effects of doubling atmospheric CO 2 concentration, [CO 2 ], on C and N allocation within pedunculate oak plants ( Quercus robur L.) grown in containers under optimal water supply. A short‐term dual 13 CO 2 and 15 NO 3 − labelling experiment was carried out when the plants had formed their third growing flush. The 22‐week exposure to 700 μl l −1 [CO 2 ] stimulated plant growth and biomass accumulation (+53% as compared with the 350 μl l −1 [CO 2 ] treatment) but decreased the root/shoot biomass ratio (‐23%) and specific leaf area (‐18%). Moreover, there was an increase in net CO 2 assimilation rate (+37% on a leaf dry weight basis; +71% on a leaf area basis), and a decrease in both above‐ and below‐ground CO 2 respiration rates (‐32 and ‐26%, respectively, on a dry mass basis) under elevated [CO 2 ]. 13 C acquisition, expressed on a plant mass basis or on a plant leaf area basis, was also markedly stimulated under elevated [CO 2 ] both after the 12‐h 13 CO 2 pulse phase and after the 60‐h chase phase. Plant N content was increased under elevated CO 2 (+36%), but not enough to compensate for the increase in plant C content (+53%). Thus, the plant C/N ratio was increased (+13%) and plant N concentration was decreased (‐11%). There was no effect of elevated [CO 2 ] on fine root‐specific 15 N uptake (amount of recently assimilated 15 N per unit fine root dry mass), suggesting that modifications of plant N pools were merely linked to root size and not to root function. N concentration was decreased in the leaves of the first and second growing flushes and in the coarse roots, whereas it was unaffected by [CO 2 ] in the stem and in the actively growing organs (fine roots and leaves of the third growth flush). Furthermore, leaf N content per unit area was unaffected by [CO 2 ]. These results are consistent with the short‐term optimization of N distribution within the plants with respect to growth and photosynthesis. Such an optimization might be achieved at the expense of the N pools in storage compartments (coarse roots, leaves of the first and second growth flushes). After the 60‐h 13 C chase phase, leaves of the first and second growth flushes were almost completely depleted in recent 13 C under ambient [CO 2 ], whereas these leaves retained important amounts of recently assimilated 13 C (carbohydrate reserves?) under elevated [CO 2 ].