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Species-specific variation of photosynthesis and mesophyll conductance to ozone and drought in three Mediterranean oaks

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  • Yasutomo Hoshika
  • Elena Paoletti
  • Mauro Centritto
  • Marcos Thiago Gaudio Gomes
  • Jaime Puértolas
  • Matthew Haworth
Article numbere13639
<mark>Journal publication date</mark>28/02/2022
<mark>Journal</mark>Physiologia Plantarum
Issue number1
Number of pages14
Publication StatusPublished
Early online date15/02/22
<mark>Original language</mark>English


Mesophyll conductance (g ) is one of the most important components in plant photosynthesis. Tropospheric ozone (O ) and drought impair physiological processes, causing damage to photosynthetic systems. However, the combined effects of O and drought on g are still largely unclear. We investigated leaf gas exchange during mid-summer in three Mediterranean oaks exposed to O (ambient [35.2 nmol mol as daily mean]; 1.4 × ambient) and water treatments (WW [well-watered] and WD [water-deficit]). We also examined if leaf traits (leaf mass per area [LMA], foliar abscisic acid concentration [ABA]) could influence the diffusion of CO inside a leaf. The combination of O and WD significantly decreased net photosynthetic rate (P ) regardless of the species. The reduction of photosynthesis was associated with a decrease in g and stomatal conductance (g ) in evergreen Q. ilex, while the two deciduous oaks (Q. pubescens, Q. robur) also showed a reduction of the maximum rate of carboxylation (V ) and maximum electron transport rate (J ) with decreased diffusive conductance parameters. The reduction of g was correlated with increased [ABA] in the three oaks, whereas there was a negative correlation between g with LMA in Q. pubescens. Interestingly, two deciduous oaks showed a weak or no significant correlation between g and ABA under high O and WD due to impaired stomatal physiological behaviour, indicating that the reduction of P was related to g rather than g . The results suggest that g plays an important role in plant carbon gain under concurrent increases in the severity of drought and O pollution.