酸胁迫对夏枯草叶绿素荧光特性和根系抗氧化酶活性的影响

为了阐明夏枯草幼苗对酸性环境的耐受性,采用不同pH值(pH=4.5、4.0、3.5、3.0)的Hoagland营养液模拟酸胁迫环境,研究酸胁迫对夏枯草幼苗叶绿素荧光特性及根系抗氧化酶活性的影响。结果表明,随着pH值下降,代表供体与受体侧参数的K点相对可变荧光(W_K)、J点相对可变荧光(V_J)和电子受体QA-被还原的最大速率(dV/dt_o)逐渐升高,光系统Ⅱ(PSⅡ)电子传递的量子效率(φE_o)降低;表示单位反应中心吸收(ABS/RC)、捕获(TR_o/RC)、热耗散(DI_o/RC)的能量逐渐增加;用于电子传递的能量(ET_o/RC)逐渐下降;表示PSⅡ的最大光化学效率(F_v/F_m)、吸收光能为基础的光合性能指数(PI_abs)、表征光系统Ⅰ(PSⅠ)的最大氧化还原活性(ΔI/I_o)及PSⅡ与PSⅠ协调性(Φ_PSⅠ/PSⅡ)随酸胁迫程度增加逐渐下降。夏枯草根系超氧化物歧化酶(SOD)与过氧化物酶(POD)活性呈下降趋势,而根系抗坏血酸过氧化物酶(APX)活性先升高后降低;夏枯草叶片可溶性糖、脯氨酸含量逐渐上升。酸胁迫下,夏枯草PSⅡ反应中心受损,电子传递受阻,光系统性能及PSⅡ与PSⅠ的协调性降低,根系SOD与POD活性受到抑制,在pH 3.0处理下表现较为明显。夏枯草通过提高单位反应中心的热耗散能力来减少过剩光能对叶片光合机构的破坏,通过提高根系APX抗氧化酶及叶片渗透调节物质含量来减少酸胁迫带来的伤害。

Effects of acid stress on chlorophyll fluorescence characteristics and root antioxidant activity of Prunella vulgaris

This research aimed to elucidate the tolerance of Prunella vulgaris seedlings to acid environments. Hoagland nutrient solutions with a range of pH values (pH=4.5, 4.0, 3.5, 3.0) were used to simulate environmental acid stress, and the effects of acid stress on chlorophyll fluorescence characteristics and root antioxidant activity were studied. It was found that at lower pH the quantum efficiency of PSⅡ electron transfer (φE_o) in leaves of P. vulgaris decreased, while a number of other fluorescence parameters increased, including: the variable fluorescence F_k to the amplitude F_j-F_o (W_K), relative variable fluorescence at J step (V_J), QA- maximum rate of reduction (dV/dt_o). The absorption flux per reaction center (ABS/RC), trapped energy flux per RC (TR_o/RC) and dissipated energy flux per RC (DI_o/RC) increased, but electron transport flux per RC (ET_o/RC) decreased gradually. The maximum quantum yield of PSⅡ (F_v/F_m), the photosynthetic index based on absorption basis (PI_abs), the maximum PSⅠ redox activity (ΔI/I_o), and the coordination of photosystem between Ⅰ and Ⅱ (Φ_PSⅠ/PSⅡ) all decreased under acid stress. The activity of superoxide dismutase (SOD) and peroxidase (POD) in roots decreased, but the activity of ascorbic acid peroxidase (APX) in roots increased on initial exposure to acid stress and then decreased. The soluble sugar and proline concentrations in leaves of P. vulgaris increased with the decrease in pH value. In summary, the PSⅡ reaction center of P. vulgaris was damaged, the electron transfer was blocked, the photosystem performance and the coordination of photosystem between Ⅰ and Ⅱ were reduced under acid stress, and the activities of SOD and POD in roots were inhibited, the latter being most obvious in the pH 3.0 treatment. P. vulgaris was able to reduce the damage to the photosynthetic mechanism by increasing the heat dissipation capacity of unit reaction center, and reduce the damage caused by acid stress by increasing the APX activity in roots and the concentration of osmolytes in leaves.