臭氧胁迫对植物主要生理功能的影响

近年来,由于光化学反应的臭氧前体增加,全球植物受对流层臭氧(O3)胁迫的程度越来越严重。臭氧污染被认为是造成东欧、西欧和整个美国的大片森林衰退和枯死的主要原因。臭氧胁迫严重影响植物叶片对光能的利用,通过气孔限制和非气孔限制,导致其光合速率的降低,影响光合产物的产量。臭氧对植物的影响与植物体内代谢物质的积聚量紧密联系。臭氧胁迫引发植物的各种防御保护机制,刺激抗氧化系统,影响膜系统,改变其体内碳和矿质养分的吸收并引起它们的重新分配,诱导其基因表达的深层变化。为了适应臭氧胁迫环境,植物通过生理生化机制的调节来保证其生命活动。如细胞通过调节渗透物质的含量来保持渗透势的平衡;细胞内各种抗氧化酶活性增加,以清除自由基,避免或者减轻细胞受到伤害;改变代谢途径以保持能量储备和降低代谢速率。可见,生态环境对生物进化具有重要影响。这个观点将在臭氧胁迫对植物生理的影响中得到证实,也是生物进化论的另一种证据。综述了臭氧对光合生理、呼吸代谢、抗氧化系统、膜系统、矿质养分的吸收和分配与分子生理等主要生理功能的影响,并提出臭氧胁迫对植物生理影响的今后研究方向与未来研究热点是:(1)加强在植物个体和群落水平上臭氧胁迫对植物生理影响的研究;(2)臭氧影响下植物的基因调控和相关信号传递网络系统的机理;(3)通过分子标记、基因图谱、基因组学和转基因技术等方法研究选育适应臭氧胁迫环境的植物;(4)尽可能在接近自然条件的环境中开展研究;(5)臭氧胁迫对亚热带和热带森林及其树种主要生理功能影响的研究;(6)建立模型评估臭氧对植物的影响。

Effects of ozone stress on major plant physiological functions

Nowadays, with the increase of ozone precursor caused by photochemical reactions, the extent of global plants suffering from ozone stress in the troposphere is getting more and more serious. Ozone pollution has been considered to be the primary cause of forest decline and tree dieback in Eastern and Western Europe and throughout the United States. Ozone stress could have strong impacts on the utilization of light and the production of photosynthesis products in plants, and lead to the decline of photosynthetic rate through stomatal limitation and non-stomatal limitation. The effects of ozone on plants are closely related to the accumulation of metabolic substance in plants. Various defensive protection mechanisms are initiated by ozone stress, such as antioxidant system and membrane system. Ozone stress has changed the absorption of carbon and mineral nutrients in plants and caused their redistribution. And it could also induce deep changes in gene expression. In order to adapt to the environment with ozone stress, plants adjust their physiological and biochemical mechanism to ensure their vital movement. For example, the content of permeable mass would be regulated by cell to maintain osmotic potential balance, meanwhile the metabolic pathway would be changed to keep energy reserves and reduce metabolic rate in plants. And all kinds of antioxidant enzymes' activity in the cell would increase to clear up free radicals and mitigate or even avoid cell damages. It's clear that the ecological environment has important effects on biological evolution. And it's confirmed by the plants' physiological effects from ozone stress, which is also another kind of evidence of biological evolutionism. In this paper, the impacts that ozone does to plants' photosynthetic physiology, respiratory metabolism, antioxidant system, membrane system, nutrients absorption and allocation, and molecular physiology were summarized to get a more comprehensive understanding of the physiological and biochemical mechanism of plants adapting to ozone stress. Hotspots for future ozone researches should be focused on the enhancement of effects of ozone stress on plant physiology in individual and community level, the gene regulation and related mechanism of signal transmission network system of plants under ozone stress, plants breeding to adapt to the environment with ozone stress by methods such as molecular marker, gene mapping, genomics approach and transgenic technology, research condition that should be close to natural environment as much as possible, the effects of ozone stress on major physiological functions of subtropical and tropical forests, and the models to assess the impacts of ozone on plants.