The use of low [CO₂] to estimate diffusional and non‐diffusional limitations of photosynthetic capacity of salt‐stressed olive saplings

• M. CENTRITTO

• F. LORETO

• K. CHARTZOULAKIS

抄録

In this study it has been shown that increased diffusional resistances caused by salt stress may be fully overcome by exposing attached leaves to very low [CO 2 ] (∼ 50  µ mol  mol −1 ), and, thus a non‐destructive‐ in vivo method to correctly estimate photosynthetic capacity in stressed plants is reported. Diffusional (i.e. stomatal conductance, g s , and mesophyll conductance to CO 2 , g m ) and biochemical limitations to photosynthesis ( A ) were measured in two 1‐year‐old Greek olive cultivars (Chalkidikis and Kerkiras) subjected to salt stress by adding 200 m m NaCl to the irrigation water. Two sets of A – C i curves were measured. A first set of standard A – C i curves (i.e. without pre‐conditioning plants at low [CO 2 ]), were generated for salt‐stressed plants. A second set of A – C i curves were measured, on both control and salt‐stressed plants, after pre‐conditioning leaves at [CO 2 ] of ∼ 50  µ mol mol −1 for about 1.5 h to force stomatal opening. This forced stomata to be wide open, and g s increased to similar values in control and salt‐stressed plants of both cultivars. After g s had approached the maximum value, the A – C i response was again measured. The analysis of the photosynthetic capacity of the salt‐stressed plants based on the standard A – C i curves, showed low values of the J max (maximum rate of electron transport) to V cmax (RuBP‐saturated rate of Rubisco) ratio (1.06), that would implicate a reduced rate of RuBP regeneration, and, thus, a metabolic impairment. However, the analysis of the A – C i curves made on pre‐conditioned leaves, showed that the estimates of the photosynthetic capacity parameters were much higher than in the standard A – C i responses. Moreover, these values were similar in magnitude to the average values reported by Wullschleger ( Journal of Experimental Botany 44, 907–920, 1993) in a survey of 109 C 3 species. These findings clearly indicates that: (1) salt stress did affect g s and g m but not the biochemical capacity to assimilate CO 2 and therefore, in these conditions, the sum of the diffusional resistances set the limit to photosynthesis rates; (2) there was a linear relationship ( r 2  = 0.68) between g m and g s , and, thus, changes of g m can be as fast as those of g s ; (3) the estimates of photosynthetic capacity based on A – C i curves made without removing diffusional limitations are artificially low and lead to incorrect interpretations of the actual limitations of photosynthesis; and (4) the analysis of the photosynthetic properties in terms of stomatal and non‐stomatal limitations should be replaced by the analysis of diffusional and non‐diffusional limitations of photosynthesis. Finally, the C 3 photosynthesis model parameterization using in vitro ‐measured and in vivo ‐measured kinetics parameters was compared. Applying the in vivo ‐measured Rubisco kinetics parameters resulted in a better parameterization of the photosynthesis model.

収録刊行物

• Plant, Cell & Environment

  Plant, Cell & Environment 26 (4), 585-594, 2003-04

  Wiley

キーワード

• Plant Science
• Physiology

詳細情報

• CRID: 1361137044848384768
• NII論文ID: 30014949877
• DOI: 10.1046/j.1365-3040.2003.00993.x
• ISSN: 13653040
• ISSN: 01407791
• Web Site: https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-3040.2003.00993.x
• Web Site: https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-3040.2003.00993.x
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