Pääkkönen E, Seppänen S, Holopainen T, Kokko H, Kärenlampi S, Kärenlampi L, Kangasjärvi J
Department of Ecology and Environmental Science, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland.
To whom correspondence should be addressed. E-mail:
New Phytol. 1998 Feb;138(2):295-305. doi: 10.1046/j.1469-8137.1998.00898.x.
Well watered (WW) or drought-stressed (DS) saplings of ozone-sensitive and ozone-tolerant (less sensitive) birch (Betula pendula Roth) clones were exposed for 43 d to 0 nl l or 100 nl l ozone. Relative growth rates of leaves, stem, and roots, leaf discolouration, stomatal conductance and induction of genes encoding stress-related proteins PR-10, PAL and a LEA-group protein BP8 were determined. In general, both ozone and drought stress, singly and in combination, increased transcript levels of PR-10 in both clones. This was related to lower induction of PAL (except in older leaves of the tolerant clone), and increased proportions of visibly injured and yellowed leaves in ozone-exposed plants. The clones differed in their stomatal conductance and growth responses. In the less sensitive clone 2, ozone did not affect growth rates, but high stomatal conductance was observed in WW ozone-exposed plants. The more sensitive clone 5 showed, on the contrary, reduced growth rates and low stomatal conductance in WW ozone plants. Interestingly, clone 2 was sensitive to drought stress alone, whereas clone 5 was highly sensitive to ozone and drought stress experienced together. The results show that appearance of visible injuries (necrotic flecks) and enhanced yellowing of leaves coincided with the induction of genes for stress proteins PR-10 and PAL. The short-term growth responses, however, seemed to be separate processes. Additionally, stomatal conductance was related to leaf injuries and growth rates in a complicated manner, emphasizing the complex nature of ozone sensitivity/tolerance mechanisms in birch.
对臭氧敏感和耐臭氧（较不敏感）的白桦（垂枝桦）克隆植株的幼苗进行充分浇水（WW）或干旱胁迫（DS）处理，使其暴露于0 nl l或100 nl l的臭氧环境中43天。测定了叶片、茎和根的相对生长速率、叶片变色情况、气孔导度以及编码与胁迫相关蛋白PR-10、PAL和一种LEA族蛋白BP8的基因的诱导情况。总体而言，单独或联合的臭氧胁迫和干旱胁迫均使两个克隆植株中PR-10的转录水平升高。这与PAL诱导水平降低（耐臭氧克隆植株的老叶除外）以及臭氧处理植株中可见损伤和发黄叶片比例增加有关。两个克隆植株在气孔导度和生长反应方面存在差异。在较不敏感的克隆2中，臭氧不影响生长速率，但充分浇水且暴露于臭氧环境中的植株气孔导度较高。相反，较敏感的克隆5在充分浇水且暴露于臭氧环境中的植株中生长速率降低且气孔导度较低。有趣的是，克隆2仅对干旱胁迫敏感，而克隆5对同时经历的臭氧和干旱胁迫高度敏感。结果表明，可见损伤（坏死斑点）的出现和叶片发黄加剧与胁迫蛋白PR-10和PAL基因的诱导同时发生。然而，短期生长反应似乎是独立的过程。此外，气孔导度与叶片损伤和生长速率之间的关系复杂，这突出了白桦中臭氧敏感性/耐受性机制的复杂性。
