不同生境下濒危植物膝柄木幼树的生态适应性

Ecological adaptability of endangered plant

关键词:  生境, 光照, 膝柄木,幼树, 生态适应性

Key words:  habitat, illumination, Bhesa robusta sapling, ecological adaptability

摘要:

膝柄木是我国极度濒危植物,也是广西滨海过渡带天然植被的重要组成树种。为了解光因子对膝柄木天然更新的限制影响,该文对林缘、林窗、林下三种不同光照生境下膝柄木幼树的生理和生长指标的年际变化特征进行了研究。结果表明:(1)光合有效辐射不足影响了膝柄木幼树的生长。林下幼树的地径、株高和叶面积增长量显著降低,而生长于光照充足林缘生境的膝柄木幼树,其生长指标增长量最大。(2)随着光合有效辐射的减少,膝柄木幼树的超氧化物岐化酶(SOD)和过氧化氢酶(CAT)的活性、可溶性蛋白含量、相对电导率和丙二醛(MDA)含量林缘生境显著高于林下生境的幼树,游离脯氨酸含量林下生境的幼树显著高于林缘和林窗生境的幼树。(3)随着光合有效辐射的减弱,林下生境幼树的叶绿素a、叶绿素b、类胡萝卜素含量均高于林缘和林窗的膝柄木幼树,而叶绿素a/b林缘幼树较高; 林缘生境的膝柄木幼树净光合速率(P_n)、蒸腾速率(T_r)在三种生境中最高; 林下生境的膝柄木幼树的胞间 CO₂浓度(C_i)高于其他两种生境,而水分利用效率(WUE)在2—4月林缘生境的膝柄木幼树最高,6—10月林下生境的膝柄木幼树高于其他两种生境,12月三种生境差异不显著。综上结果表明,光照因子是膝柄木幼树时期生长的限制因子之一,生长在林缘生境的幼树因接收到的光照较为充足,其生长状况要显著好于其他生境的幼树。

Abstract:

Bhesa robusta is a critically endangered plant in China, which also is an important component of natural vegetation in the coastal ecotone of Guangxi. In order to learn about whether the light factor has the effects on the natural regeneration of B. robusta saplings or not, the interannual variation characteristics of physiological and growth indexes of B. robusta saplings under three different photosynthetic habitats of forest edge, forest gap, and understory were studied. The results were as follows:(1)The deficiency of photosynthesis active radiation affected the growth of B. robusta saplings, the growth of ground diameter, plant height, and leaf area of understory saplings decreased significantly, while the growth index of saplings growing in the forest edge with sufficient light was the largest.(2)With the decrease of photosynthesis active radiation, the contents of superoxide dismutase(SOD)and catalase(CAT), soluble protein, relative electrical conductivity, and malonaldehyde(MDA)of the B. robusta saplings under forest edge habitat were significantly higher than those in the understory habitat, and the free proline content of B. robusta sapling under the understory habitat were significantly higher than in forest edge and forest gap habitat.(3)With the decrease of photosynthesis active radiation, the photosynthetic pigment index chlorophyll a, chlorophyll b, carotenoids of B. robusta sapling were increased in the understory habitat, and the chlorophyll a/b ratio of B. robusta sapling was higher in the forest edge habitat; The net photosynthetic rate(P_n)and transpiration rate(T_r)on the photosynthesis physiological target of B. robusta saplings in forest edge habitat were higher than those in understory and forest gap habitats; The intercellular CO₂ concentration(C_i)and water use efficiency(WUE)of B. robusta sapling in the understory were higher than those in forest gap and forest edge habitats. And WUE was the highest in the forest edge habitat from February to April, WUE of B. robusta saplings in the understory habitat were higher than those of the other two habitats in June to October, and there were almost no differences between the three habitats in December. All the above results indicate that the light factor is one of the limiting factors during the growth period of B. robusta sapling, and the growth of B. robusta sapling in the forest edge habitat is significantly better than that in the forest gap and understory habitats because of the abundant sunlight.