水分胁迫对滇润楠和香樟幼苗叶绿素荧光和叶水势的影响

以一年生云南乡土树种滇润楠和引进外来树种香樟幼苗为试验材料,研究不同程度的水分胁迫对二树种幼苗叶绿素荧光和叶水势的影响。干旱初期当植物的叶水势尚无明显变化时,植物的可变荧光(Fv)、PSⅡ最大光化学效率(Fv/Fm)和PSⅡ的潜在活性(Fv/F_0)都有明显下降,而初始荧光(F_0)增加明显,说明此时干旱胁迫已经对二树种幼苗叶绿素荧光产生强烈的抑制作用。随着水分胁迫程度的加剧导致幼苗PSⅡ反应中心受到破坏,二树种幼苗的叶水势以及各种荧光指标发生不同规律性变化。相对而言,香樟幼苗的叶水势下降较快,其叶绿素荧光各个指标变化均大于滇润楠,说明香樟对水分胁迫较敏感,滇润楠的耐旱性较强。

Effect of Drought Stress on Seedling Chlorophyll Fluorescence and Leaf Water Potential of Machilus yunnanensis and Cinnamomum camphora

Effect of drought stress on chlorophyll fluorescence and leaf water potential of one-year-old seedlings of the native tree species Machilus yunnanensis from Yunnan Province and the introduced tree species Cinnamomum camphora was studied. It was showed that the major fluorescence indexes including the variable fluorescence ( Fv),the maximum photochemical efficiency of PS Ⅱ (Fv/Fm) and the latent activity of PS Ⅱ (Fv/Fo) dropped obviously, while the primary fluorescence (Fo) increased obviously at the initial stage of water stress when there was no distinct change to leaf water potential, showing that the drought stress had already strongly inhibited the chlorophyll fluorescence of seedlings for both species. Along with the drought stress development, there were varied regular variations in leaf water potential and the parameters of chlorophyll fluorescence happened to seedlings of each studied tree species. Compared with M. yunnanensis, the leaf water potential and each parameter of chlorophyll fluorescence of C. camphora seedlings changed more heavily, indicating that C. camphora was more sensitive to drought stress and M. yunnanensis had stronger capacity of drought resistance.