不同种源栓皮栎幼苗叶片水分关系和保护酶活性对干旱胁迫的响应

 为了鉴别不同种源的栓皮栎（Quercus variabilis）耐旱性，对4个种源的3年生盆栽幼苗进行了控制条件下的土壤干旱胁迫实验，系统测定了超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性、MDA（丙二醛）含量、膜透性，以及叶片P-V曲线导出的水分关系参数（Ψπsat、Ψπtlp、WSDtlp、εmax）。结果表明：在土壤干旱胁迫下，种源4（黄龙）和种源3 (秦岭北坡) 抗氧化能力较强， 种源2 (伏牛山)居中, 种源1（巴山）的表现最差。干旱胁迫使各种源 MDA的含量及膜透性均有不同程度的提高，其中种源4的MDA含量及膜透性比较平稳, 种源1变化剧烈。在干旱胁迫下,各种源渗透调节和保持膨压的能力均有提高，但存在差异，以种源4和种源3表现较好，种源2居中，种源1较差。应用Fuzzy方法，对不同种源的叶片水分关系参数、保护酶活性和膜透性在干旱胁迫中的动态进行综合评判，认为不同种源的耐旱性强度次序为：种源4>种源3>种源2>种源1。其中种源4与种源1和种源2差异显著(p<0.05)。

WATER RELATIONS AND ACTIVITY OF CELL DEFENSE ENZYMES TO WATER STRESS IN SEEDLING LEAVES OF DIFFERENT PROVENANCES OF QUERCUS VARIABILIS

Quercus variabilis is an important economic tree because it not only provides timber and firewood for local farmers, but also is used to produce cork, tannin extract, and edible fungi for commercial use. It is distributed in 22 provinces in China from sub-tropical to temperate regions and at altitudes that range from 50 to 2 000 m. It also plays an important role in the conservation of water and soil. However, little is known about the physiological tolerance mechanisms of drought stress. In order to discriminate among the drought-tolerant characteristics of different Q. variabilis provenances, we conducted a drought stress experiment using potted 3-year old seedlings of four provenances from different regions. Changes in superoxide dismutas activity (SOD), catalase activity (CAT), malondial dehyde content (MDA), electrolyte leakage rate, osmotic potential at saturation (ψπsat), osmotic potential at turgor loss point (Wπtlp), water saturation deficit at turgor loss point (WSDtlp), and modulus of elasticity (εmax) of leaves were measured and analysed as soil drought conditions developed. Under similar conditions of soil drought stress, provenance 4 (from Huanglong Mt. in the loess plateau) and provenance 3 (from the north slope of Qinling Mt.) revealed more antioxidant ability than provenance 2 (from Funiu Mt.) and provenance 1 (from the north slope of Bashan Mt.). During the development of soil drought stress, the MDA content and electrolyte leakage rate were enhanced to different extents in the four provenances; the greatest change was provenance 1 and the lowest change in provenance 4. The activities of SOD and CAT increased at the beginning of stress conditions but decreased at the end of the drought stress period. All provenances had the ability to maintain turgor and osmotic adjustment throughout the experiment but distinct differences among provenances were apparent: provenance 4 and provenance 3 had greater turgor maintenance and osmotic adjustment while provenance 1 performed the worst. Using Fuzzy synthetic evaluation of the parameters of water relations and the activities of two cell defense enzymes to water stress in leaves, the level of drought-tolerance among the four provenances decreased in the following order: provenance 4> provenance 3> provenance 2> provenance 1. Among the four provenances, provenance 4 was significantly different from the provenance 2 and provenance 1 (p<0.05). Differences in the drought tolerant characteristics of the four provinces resulted from long-term evolution and adaptation to their particular environmental conditions and are most likely genetically controlled. Therefore, these characteristics should be used for selecting and identifying drought tolerant provenances for use in forest management and restoration of Q. variabilis in arid regions.