不同海拔长白山岳桦的生理变化

通过分析长白山国家级自然保护区内不同海拔(A1:1700 m, A2:1800 m, A3:1900 m, A4:2000 m, A5:2050 m)梯度岳桦叶片中各种生理指标含量的变化,探讨了林线树木适应高山环境的生理机制.结果表明:随着海拔的升高,比叶面积(SLA)显著减小,A5与A1相比下降了35.90%,差异达到显著水平;叶绿素含量随海拔梯度升高而降低,但叶绿素a/b比值(Chla/Chlb)和Car的相对含量(Car/Chl)随海拔梯度升高而增加;在海拔1900 m左右,MDA含量和MP均处于最低水平,各种酶的活性均为最低;当海拔超过2000 m,接近森林分布的界限时,MDA含量和MP升高,并达到最大值,各种酶的活性都出现了一定程度的下降.综合本次研究表明, 在海拔1900 m比较适合岳桦的生长;海拔超过2000 m,岳桦体内生理抗性下降,不利于岳桦的生长发育,因此高海拔限制了岳桦的分布.

Physiological response of Betula ermanii at different altitudes in Changbai Mountain

To study the physiological mechanisms in environment adaptation of Betula ermanii in treeline of Changbai Mountain, a National Nature Reserve of China, the specific leaf area (SLA), content of Chl(a+b), malondialdehyde (MDA) and the membrane permeability (MP), and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in leaves of B. ermanii from different altitudes (A1: 1700 m, A2: 1800 m, A3: 1900 m, A4: 2000 m and A5: 2050 m) were investigated. The results showed that SLA decreased conspicuously with increasing altitude, compared with that in A1, it decreased significantly 35.90% in A5; Chl(a+b) reduced with increasing altitude, however Chla/Chlb and Car/Chl increased with elevation; At 1900 m, the content of MDA and MP reached minimum values, as well as the activity of SOD, POD, CAT and APX in B. ermanii leaves, when the altitude near the upper limit of forest vertical distribution, the content of MDA and MP increased and reached maximum values, but the activity of SOD, POD, CAT and APX reduced in some degree. In general, 1900 m is the best for the growth of B. ermanii; while above 2000 m, the physical resistance of B. ermanii declined, which is not conducive to the growth and development. Therefore, a higher elevation may limit its distribution.