Role Of Antioxidant Defense System And Biochemical Adaptation On Stress Tolerance Of Alpine Plants Rhodiola Quadrifida And R.gelida

Alpine environment are characterized by low temperature, high light intensities and short growing periods. This combination leads to high light stress owing to the imbalance between light energy harvesting and its use in photochemistry. In extreme cases, high light stress can lead to the level of photo-oxidative damage exceeding the rate of repair to the photosynthetic apparatus. Plant species may vary in the mechanisms they use to prevent photodamage. High mountain plants must have special physiological and biochemical mechanisms to survive under extreme conditions. To study the mechanisms of adaptation of high mountain plants, we investigated the antioxidative defense capacity, photosynthesis pigments, osmotic solute, polyamine in leaves of two high mountain plants, Rhodiola quadrifida and R gelida. Field investigations were carried out on the slopes of Tianshan Mountain near the Tianshan Glacier No.1. Along this slope, R quadrifida was found between 3605m-3850m altitude and R. gelida was found between 3851m-4000m altitude. Our results showed:1. The significantly increase in the activities of antioxidative enzymes ,such as SOD, APX, GR, DHAR, MDAR as well as the pool size and reductive state of antioxidants GSH and AsA in Ascorbate-glutathione cycle and CAT, POD enzymes activities, in the leaves of R. quadrifida suggested a combined and balanced enhancement of antioxidants to improve stress resistance in high mountain plants leaves.2. Antioxidative defense mechanism can be vitally important in the survival of R. quadrifida and R. gelida. However, the present study clearly shows that these two alpine plants may not need all the components of antioxidant protection. Instead, the antioxidants in ascorbate-glutathione cycle increased in R. quadrifida, while R. gelida had high content of α -tocopherl.3. R. quadrifida had high content of Spm, while R. gelida had high content of Spd.4. R gelida had significant high content of proline and soluble proteins, while the content of soluble sugar and sucrose was distinctively high in the leaves of R quadrifida.5. Our study showed R. quadrifida was more sensitive to the photo-oxidative damage than Rgelida. And the high ratio of carotenoid/chlorophyll in Rgelida might helpful in the protection from photo-oxidative damage.