Apparent respiratory discrimination is correlated with growth rate in the shoot apex of sunflower (Helianthus annuus)
Open Access
- 24 September 2004
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Experimental Botany
- Vol. 55 (408) , 2599-2605
- https://doi.org/10.1093/jxb/erh263
Abstract
The literature offers no consensus as to whether the δ13C of respired CO2 is identical to that of the respiratory substrate, perhaps because of differences in measurement technique and growth conditions. To address this issue, the δ13C of respired CO2 from growing sunflower shoot apices was measured and compared with that of soluble carbohydrates extracted from the respiring tissues. Shoot apices were studied because any influence of growth and biosynthesis was expected to be maximally expressed in these rapidly growing tissues. The two most probable substrates, starch and soluble sugars, were similar in δ13C (P=0.46). The δ13C of respired CO2 was enriched in 13C compared with these putative substrates (PPP2 is enriched relative to its substrates. Variation in growth rates may help to explain the variable amounts of respiratory discrimination described in the literature.Keywords
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