期刊
PLANT CELL AND ENVIRONMENT
卷 32, 期 7, 页码 796-810出版社
WILEY
DOI: 10.1111/j.1365-3040.2009.01959.x
关键词
decarboxylation; Farquhar model; mesophyll conductance; p(i)/p(a)
资金
- Institute of Geophysics and Planetary Physics at Los Alamos National Laborator [95566-001-05]
- National Science Foundation [IOS-0719118]
We present field observations of carbon isotope discrimination (Delta) and internal conductance of CO2 (g(i)) collected using tunable diode laser spectroscopy (TDL). Delta ranged from 12.0 to 27.4 parts per thousand over diurnal periods with daily means from 16.3 +/- 0.2 parts per thousand during drought to 19.0 +/- 0.5 parts per thousand during monsoon conditions. We observed a large range in g(i), with most estimates between 0.04 and 4.0 mu mol m(-2) s(-1) Pa-1. We tested the comprehensive Farquhar, O'Leary and Berry model of Delta (Delta(comp)), a simplified form of Delta(comp) (Delta(simple)) and a recently suggested amendment (Delta(revised)). Sensitivity analyses demonstrated that varying g(i) had a substantial effect on Delta(comp), resulting in mean differences between observed Delta (Delta(obs)) and Delta(comp) ranging from 0.04 to 9.6 parts per thousand. First-order regressions adequately described the relationship between Delta and the ratio of substomatal to atmospheric CO2 partial pressure (p(i)/p(a)) on all 3 d, but second-order models better described the relationship in July and August. The three tested models each best predicted Delta(obs) on different days. In June, Delta(simple) outperformed Delta(comp) and Delta(revised), but incorporating g(i) and all non-photosynthetic fractionations improved model predictions in July and August.
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