1. Yonekura, T., Honda, Y., Oksanen, E., Yoshidome, M., Watanabe, M., Funada, R., Koike, T. and Izuta, T. (2001) The influences of ozone and soil water stress, singly and in combination, on leaf gas exchange rates, leaf ultrastructural characteristics and annual ring width of Fagus crenata seedlings. Journal of Japan Society for Atmospheric Environment, Vol. 36, No. 6, 333-351.
Abstract
The effects of ozone (O3) and soil water stress, singly and in combination, on leaf gas exchange rates, leaf ultrastructural characteristics and annual ring width of Fagus crenataseedlings were investigated. Three-year-old seedlings were exposed to charcoal-filtered air (< 5 nmol mol-1 O3) or 60 nmol mol-1 O3 7 hours per day (11:00～18:00), for 156 days from 10 May to 12 October 1999 in naturally-lit growth chambers at 20/15℃ (day/night). During the same period, half of the seedlings in each gas treatment received 250 mL of water at the 3-day-intervals (well-watered treatment), while the rest received 175 mL of water at the same intervals (water-stressed treatment). The long-term and mild soil water stress induced significant reductions in leaf water potential after July, and then the net photosynthetic rate at 350 μmol mol-1 CO2 (A350), stomatal diffusive conductance to water vapor and transpiration rate were significantly reduced after August. In addition, the diameter of plastoglobuli in the chloroplasts was significantly increased by the soil water stress. The O3 caused significant reductions in A350, maximum net photosynthetic rate at saturated CO2-concentaration (Amax), carboxylation efficiency of photosynthesis (CE) and dark-adapted maximum chlorophyll fluorescence (Fv/Fm). The O3-induced reduction in the net photosynthetic rate was firstly due to the reduction in the quantity and/or activity of RuBP carboxylase/oxygenase (Rubisco), and then due to the reductions in the regeneration rate of RuBP and activity of photochemical system in the chloroplasts. Furthermore, the size of starch grain in the chloroplasts and annual ring width were significantly reduced, whereas the diameter of plastoglobuli was significantly increased by O3. No significant interaction between O3 and soil water stress were observed with the leaf gas exchange rate, leaf water potential, ultrastructural characteristics of leaf mesophyll tissue and annual ring width throughout the one-growing period. Based on the results of the present study, we concluded that the photosynthesis and structural characteristics of Faguscrenata are affected by ambient levels of O3 and long-term mild water stress, and these two stresses are related to the decline of this tree in Japanese mountainous areas such as Tanzawa Mountains in Kanagawa Prefecture.
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最終更新：2008年03月08日 03:59
