Physiological Responses of Two Varieties of Taxus Plants to Simulated Acid Rain Stress

  Objective  Physiological responses to imposed simulated acid rain treatment were analyzed to determine the stress tolerance of two varieties of Taxus plants.

  Method  Two-year-oldTaxus chinensis and T. yunnanensis, which are known to be resistant to acid rain, were treated by solutions of pH 4.5, 4.0, 3.5, and 3.0. Antioxidant enzyme activities and contents of chlorophyll (CHL), carotenoids (CAR), nutrients, malondialdehyde (MDA), and osmotic adjustment soluble proteins (SP) and sugars (SS) in leaves of the plants under treatments and control at pH 5.6 were measured.

  Result  The activities of APX, PPO, SOD, POD, and CAT as well as the contents of SP and SS of the plants increased and followed by a decline, while MDA increased and CHL and CAR decreased as the treatment acidity increased. The stress tolerance of the two species differed, as T. chinensis peaked at pH 4.5 and T. yunnanensis at pH 4.0. However, neither of them could withstand pH 3.0 treatment without severe ill-effects physiologically.

  Conclusion  In the simulated acid rain test, T. yunnanensis appeared to be more tolerant to the imposed stress than did T. chinensis.