Abstract:

Aims The antioxidative defense capacity of plants plays an important role in extreme environments. We investigated the antioxidative system in Picea crassifolia and Sabina przewalskiileaves along an altitudinal gradient in Sidalong forests of Qilian Mountains to study the response of antioxidative systems in evergreen xylophytes to subalpine environment.
Methods We determined the contents of malonaldehyde (MDA), praline (Pro), ascorbic acid (AsA) and glutathione (GSH), as well as the activities of superoxide dismutase (SOD) , peroxidase (POD) , catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) in leaves of P. crassifolia and S. przewalskii from different altitudes (2 665-3 365 m).
Important findings The MDA contents in P. crassifolia and S. przewalskii leaves positively and significantly correlated with altitude. At the same altitude, the MDA content in S. przewalskii leaves was significantly higher than that in P. crassifolia leaves. With increasing altitude, the content of Pro, AsA and GSH and the activities of SOD, POD, CAT, APX and GR in leaves of both P. crassifolia and S. przewalskii increased. The sensitivity of AsA, GSH and Pro in S. przewalskii leaves along the altitudinal gradient was higher than those in P. crassifolia, although the AsA content was lower than the later. Those results suggested that S. przewalskii suffered greater oxidative stress than P. crassifolia, but its capacity to cavenge O₂^-· was similar. POD was a main enzyme in S. przewalskii as decomposing H₂O₂, but P. crassifolia was CAT, APX and GR. The action of AsA-GSH circulatory system in P. crassifolia was greater than that in S. przewalskii, and Pro was the most important antioxidant substance in S. przewalskii.

Key words: Picea crassifolia, Sabina przewalskii, altitudinal gradient, antioxidative system, stress adaptation