Abstract

The potential use of chlorophyll fluorescence (CF) induction assay as a tool for screening and characterizing the tolerance of ozone (O3), contrasting cultivars of snapbeans (Phaseolus vulgaris L.), was investigated. A range of CF parameters was examined for snapbeans treated with O3. Chlorophyll fluorescence parameters such as Fo, Fmax, and Fv, Fn/Fmax were compared in O3 tolerant and susceptible snapbeans cultivars grown under O3 stress conditions. O3-stressed leaves showed significantly higher constant-yield (Fo) but greatly reduced variable fluorescence (Fv) and decreased Fv/Fmax ratios. In the O3-sensitive cultivar snapbean cv BBL-290, O3 stress resulted in a strong inhibition of the fast and slow fluorescence-induction transients and altered the form of the kinetic curves of CF in leaves. In particular, the fluorescence quenching rate and Fv/Fmax ratios were markedly decreased in O3-stressed leaves. In contrast, leaves of the O3-resistant cultivar cv Astro showed only minor changes in CF. The values of the Fv/Fmax ratio decreased in the O3-sensitive cultivar much more drastically than the O3-resistant cultivar. Based on CF measurements, it appears that O3-induced stress blocked photosynthetic electron transport between photosystem (PS) II and PS I. The close agreement between changes in fluorescence and visual symptoms of O3-induced injury suggest that the CF patterns, the rate of fluorescence-induction transients, and the Fv/Fmax ratio can provide valuable tools to investigate the photosynthetic and metabolic mechanisms affects by O3-induced stress. Chlorophyll fluorescence analysis could also be a useful technique which could be used by plant breeders to screen large numbers of plant reapidly for air pollution sensitivity.

中文摘要

利用葉綠素產生螢光的快慢及其強度變化情形，可篩選及檢定Snapbean對臭氧是否具有忍耐作用。測試葉綠素螢光強度項目有Fo, Fv及Fv/Fmax比例。 在臭氧逆境下，不抗臭氧的品系對螢光產生及其強度有很大的起伏變化，尤其是螢光消失速率及比例均顯著減少。但是具抗臭氧的品系則變化較小。由螢光的測定，可知臭氧危害作物系臭氧中斷光體系及光體系之間的電子傳遞所引起的結果。由於臭氧所引起的外表損害程度與其葉綠素螢光的變化大小有一至性，所以由螢光變化之測定，可研究作物在臭氧逆境情況下其光合作用機制及新陳代謝機制受害程度，同時也可供職務育種者作為大規模並且快速檢測作物對空氣污染物之感受程度，作為篩選品種之用。