Teuber M, Zimmer I, Kreuzwieser J, Ache P, Polle A, Rennenberg H, Schnitzler J-P
Forschungszentrum Karlsruhe GmbH, Institut für Meteorologie und Klimaforschung, Atmosphärische Umweltforschung, Garmisch-Partenkirchen, Germany.
Plant Biol (Stuttg). 2008 Jan;10(1):86-96. doi: 10.1111/j.1438-8677.2007.00015.x.
Nitrogen nutrition and salt stress experiments were performed in a greenhouse with hydroponic-cultured, salt-sensitive Grey poplar (Populus x canescens) plants to study the combined influence of different N sources (either 1 mm NO(3) (-) or NH(4)(+)) and salt (up to 75 mm NaCl) on leaf gas exchange, isoprene biosynthesis and VOC emissions. Net assimilation and transpiration proved to be highly sensitive to salt stress and were reduced by approximately 90% at leaf sodium concentrations higher than 1,800 microg Na g dry weight (dw)(-1). In contrast, emissions of isoprene and oxygenated VOC (i.e. acetaldehyde, formaldehyde and acetone) were unaffected. There was no significant effect of combinations of salt stress and N source, and neither NO(3)(-) or NH(4)(+) influenced the salt stress response in the Grey poplar leaves. Also, transcript levels of 1-deoxy-d-xylulose 5-phosphate reductoisomerase (PcDXR) and isoprene synthase (PcISPS) did not respond to the different N sources and only responded slightly to salt application, although isoprene synthase (PcISPS) activity was negatively affected at least in one of two experiments, despite high isoprene emission rates. A significant salt effect was the strong reduction of leaf dimethylallyl diphosphate (DMADP) content, probably due to restricted availability of photosynthates for DMADP biosynthesis. Further consequences of reduced photosynthetic gas exchange and maintaining VOC emissions are a very high C loss, up to 50%, from VOC emissions related to net CO(2) uptake and a strong increase in leaf internal isoprene concentrations, with maximum mean values up to 6.6 microl x l(-1). Why poplar leaves maintain VOC biosynthesis and emission under salt stress conditions, despite impaired photosynthetic CO(2) fixation, is discussed.
在温室中，对水培种植的盐敏感灰杨（Populus x canescens）植株进行了氮素营养和盐胁迫实验，以研究不同氮源（1 mM硝酸根离子或铵根离子）和盐分（高达75 mM氯化钠）对叶片气体交换、异戊二烯生物合成和挥发性有机化合物（VOC）排放的综合影响。净同化作用和蒸腾作用被证明对盐胁迫高度敏感，当叶片钠浓度高于1800 μg Na g干重（dw）-1时，它们会降低约90%。相比之下，异戊二烯和含氧VOC（即乙醛、甲醛和丙酮）的排放未受影响。盐胁迫和氮源组合没有显著影响，硝酸根离子或铵根离子均未影响灰杨叶片的盐胁迫响应。此外，1-脱氧-D-木酮糖-5-磷酸还原异构酶（PcDXR）和异戊二烯合酶（PcISPS）的转录水平对不同氮源没有响应，仅对盐分施用有轻微响应，尽管在两个实验中的至少一个实验中，异戊二烯合酶（PcISPS）活性受到负面影响，但异戊二烯排放率仍然很高。一个显著的盐效应是叶片二甲基烯丙基二磷酸（DMADP）含量大幅降低，这可能是由于用于DMADP生物合成的光合产物供应受限。光合气体交换减少和维持VOC排放的进一步后果是，与净二氧化碳吸收相关的VOC排放导致高达50%的非常高的碳损失，以及叶片内部异戊二烯浓度大幅增加，最大平均值高达6.6 μl l-1。本文讨论了为什么杨树叶片在盐胁迫条件下尽管光合二氧化碳固定受损仍能维持VOC生物合成和排放。
