东北地区5种阔叶树苗木对火烧的生理响应

以3年生水曲柳、胡桃楸、蒙古栎、黄菠萝、白桦为研究对象,研究3种火烧处理(T1处理:对叶片火烧;T2处理:对枝火烧;T3处理:对茎火烧)对幼树丙二醛(MDA)含量、叶绿素含量和净光合速率的影响。结果显示:5种幼树火害叶(T1处理)丙二醛含量与对照相比都显著提高,说明幼树叶片细胞都受到了火的影响,发生了膜脂过氧化作用。水曲柳、胡桃楸、白桦火害叶(T1处理)叶绿素含量与对照相比显著提高;水曲柳、胡桃楸火害叶(T1处理)叶绿素a/b与对照相比显著降低。火烧处理后幼树新生叶丙二醛含量的变化因物种而异。5种幼树3种火烧处理后新生叶叶绿素含量除蒙古栎的茎处理和胡桃楸的枝处理显著降低外,大多表现为升高的趋势;新生叶叶绿素a/b的变化因物种而异。5种幼树3种火烧处理后新生叶净光合速率除蒙古栎的茎处理显著降低外,其他都有不同程度的提高。表明火烧提高了幼树的光合作用能力。

Physiological responses of five deciduous broad-leaved tree seedlings in the Northeast Area of China to burning

In the present study, the effects of burning treatments on seedlings of five tree species were investigated. Using pot-grown 3-year-old seedlings of Fraxinus mandshurica, Juglans mandshurica, Quercus mongolica, Phellodendron amrense, and Betula platyphyla as the test materials, three burning treatment methods were applied, including T1 (leaf burn), T2 (branch burn), and T3 (stem burn). The malondialdehyde (MDA) and chlorophyll contents in seedling leaves were detected, and the net photosynthetic rate was determined. The heat energy from the fire treatments is transferred to plant tissues by conduction and radiation. Burning can damage cell membranes, resulting in lipid peroxidation and production of MDA. The product of lipid peroxidation, MDA, was used to estimate the degree of damage to the cell membranes. Lipid peroxidation can occur during organ senescence or as a result of stress damage. In T1 treatment, the MDA contents in leaves from five species were significantly higher than their respective controls, indicating that leaf cells were destroyed by fire and that membrane lipids in leaf cells had undergone peroxidation. Moreover, in T1 treatment, the chlorophyll contents were higher in the leaves of F. mandshurica, J. mandshurica, and B. platyphyla than in their respective controls, but similar in the leaves of Q. mongolica and P. amrense and their respective controls. In addition, in T1 treatment, the chlorophyll a/b ratio in the leaves from F. mandshurica and J. mandshurica was lower than that in controls, respectively. However, in Q. mongolica, P. amrense, and B. platyphyla, the chlorophyll a/b ratio was similar with controls. Also, there were higher MDA contents in leaves after the T2 and T3 treatments of Q. mongolica, the T3 treatment of J. mandshurica, and the T2 and T3 treatments of B. platyphyla.In terms of cell membrane stability, the membranes of species that were not well adapted to fire were weakened by fire damage. However, in seedlings that are well-adapted to fire, the MDA contents in young fire-treated leaves were lower than those in the control. These included the T1 and T2 treatments of F. mandshurica and the T2 and T3 treatments of P.amrense. The lower MDA contents in the burned tissues indicated that cell membrane stability is enhanced by fire treatments in young leaves and saplings from the well fire-adapted species. Chlorophyll reflects the photosynthesis, the chlorophyll content, and the chlorophyll a/b ratio are important indicators of the physiological condition of the leaves. In all five species, the chlorophyll contents in the leaves increased after the T1, T2, and T3 treatments, except in T3 treatment of Q. mongolica and T2 treatment of J. mandshurica. The change in the chlorophyll a/b after fire treatments varied among the five species. The net photosynthetic rate, which is the most important index for photosynthesis, increased to varying extents in the five species in the T1, T2, and T3 treatments. The only exception was the T3 treatment of Q. mongolica. Fire influenced the photosynthesis of saplings by affecting physiological metabolism. The results of these experiments indicated that fire affected the growth of these tree species.