Significance of leaf structure and emission of volatile organic compounds in ozone tolerance of oat and wheat
2012
Hartikainen, Kaisa | Kivimäenpää, Minna | Nerg, Anne-Marja | Holopainen, Toini
To study the possible differences in tropospheric ozone (O₃) tolerance of oat (Avena sativa L.) and wheat (Triticum aestivum L.), two oat and two wheat cultivars were exposed to 0, 50, or 100 nL·L–¹ O₃ concentrations in growth chambers. Measurements on volatile organic counpound emission and physiological, biochemical, and leaf structural characteristics were conducted with 2- and 4-week-old seedlings. Neither of the studied species was particularly O₃ sensitive, but O₃ sensitivity should rather be defined on the basis of the characteristics of the cultivars within species. Visible leaf injuries increased with leaf age and with increasing O₃ concentration. Net photosynthesis (Pₙ), stomatal conductance (gₛ), and chlorophyll fluorescence (Fᵥ/Fₘ) of 2-week-old seedlings were more detrimentally affected by O₃ compared with older seedlings. Wheat generally invested more in photosynthesis and related processes, such as gₛ, Fᵥ/Fₘ, concentrations of Rubisco, chlorophylls and carotenoids, and synthesis of starch compared with oat. O₃ increased Rubisco concentration in 2-week-old and carotenoid concentration in 4-week-old seedlings, especially in wheat. Lower extent of O₃-caused visible leaf injuries in the other oat cultivar can supposedly be explained by its low stomatal conductance and high monoterpene production.
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