Fares S, Loreto F, Kleist E, Wildt J
Consiglio Nazionale delle Ricerche, Istituto di Biologia Agroambientale e Forestale, Via Salaria Km 29,300, 00016 Monterotondo Scalo, Rome, Italy.
Plant Biol (Stuttg). 2008 Jan;10(1):44-54. doi: 10.1055/s-2007-965257. Epub 2007 May 31.
Volatile isoprenoids were reported to protect plants against ozone. To understand whether this could be the result of a direct scavenging of ozone by these molecules, the stomatal and non-stomatal uptake of ozone was estimated in plants emitting isoprene or monoterpenes. Ozone uptake by holm oak (Quercus ilex, a monoterpene emitter) and black poplar (Populus nigra, an isoprene emitter) was studied in whole plant enclosures (continuously stirred tank reactors, CSTR). The ozone uptake by plants was estimated measuring ozone concentration at the inlet and outlet of the reactors, after correcting for the uptake of the enclosure materials. Destruction of ozone at the cuticle or at the plant stems was found to be negligible compared to the ozone uptake through the stomata. For both plant species, a relationship between stomatal conductance and ozone uptake was found. For the poplar, the measured ozone losses were explained by the uptake of ozone through the stomata only, and ozone destruction by gas phase reactions with isoprene was negligible. For the oak, gas phase reactions of ozone with the monoterpenes emitted by the plants contributed significantly to ozone destruction. This was confirmed by two different experiments showing a) that in cases of high stomatal conductance but under low CO(2) concentration, a reduction of monoterpene emission was still associated with reduced O(3) uptake; and b) that ozone losses due to the gas phase reactions only can be measured when using the exhaust from a plant chamber to determine the gas phase reactivity in an empty reaction chamber. Monoterpenes can therefore relevantly scavenge ozone at leaf level contributing to protection against ozone.
据报道，挥发性类异戊二烯可保护植物免受臭氧侵害。为了解这是否是这些分子直接清除臭氧的结果，我们对排放异戊二烯或单萜的植物中臭氧的气孔吸收和非气孔吸收进行了估算。在全株封闭装置（连续搅拌槽式反应器，CSTR）中研究了圣栎（Quercus ilex，一种单萜排放植物）和黑杨（Populus nigra，一种异戊二烯排放植物）对臭氧的吸收。在对封闭装置材料的吸收进行校正后，通过测量反应器进出口处的臭氧浓度来估算植物对臭氧的吸收。与通过气孔吸收的臭氧相比，角质层或植物茎干处臭氧的破坏可忽略不计。对于这两种植物，均发现气孔导度与臭氧吸收之间存在关系。对于杨树，测得的臭氧损失仅由通过气孔吸收的臭氧来解释，臭氧与异戊二烯的气相反应导致的臭氧破坏可忽略不计。对于橡树，臭氧与植物排放的单萜的气相反应对臭氧破坏有显著贡献。这通过两个不同的实验得到了证实：a）在气孔导度高但二氧化碳浓度低的情况下，单萜排放的减少仍与臭氧吸收的减少相关；b）只有当使用植物箱的废气来确定空反应室中的气相反应活性时，才能测量仅由气相反应导致的臭氧损失。因此，单萜在叶片水平上可有效清除臭氧，有助于植物抵御臭氧。
