Figure 4.

Impact of water deficit (WD) on C fluxes in the Arabidopsis rosette 10 d after the onset of water deficit. All values are expressed as mg CHO g⁻¹ rosette dry weight d⁻¹ when referred to fluxes. Photosynthesis and respiration measurements on an area basis were transformed on a per dry weight basis using specific leaf area of the whole rosette. Rosette growth demand for CHO was inferred from shoot relative growth rate assuming 40% C in the dry weight. The rosette C balance (potential export to the roots) was evaluated as photosynthesis minus dark respiration minus rosette growth demand for C. Daily C turnover of the sum of the metabolites (starch, Suc, hexoses, fumarate, malate, Pro, other amino acids) was expressed as milligrams of CHO equivalents assuming an average of 4.7 C atoms per molecule of free amino acid. The estimation of the C metabolites immobilized for osmotic adjustment (OA) was based on Table II data reexpressed per gram dry weight. Two values for osmotic adjustment were inferred, either the amount of CHO required for osmotic adjustment in 1 g dry weight (lower left value) or the amount of CHO required to accompany rosette growth (value in parentheses after the flux to growth). The latter was then subtracted from C export (value in parentheses in the bottom arrow).