水分胁迫与复水对地枫皮生理生态特性的影响

Effects of water stress and rewatering on eco-physiological characteristics of Illicicum difengpi

关键词:  地枫皮, 水分胁迫, 复水, 光合参数, 叶绿素荧光

Key words:  Illicicum difengpi, water stress, rehydration, photosynthetic parameter, chlorophyll fluorescence

摘要:

以岩溶特有药用植物地枫皮为材料,研究土壤水分胁迫及复水条件下,其叶片光合参数、叶绿素荧光参数及光合色素含量的变化特性,进而探讨其对水分胁迫的生理生态适应性。结果表明:停止供水10 d,水分胁迫地枫皮叶片的P_n(净光合速率)、C_i(胞间CO₂浓度)、G_s(气孔导度)和L_s(气孔限制值) 均下降,气孔限制是P_n降低的主要原因; 停止供水15 d,水分胁迫地枫皮叶片的P_n日变化呈逐渐下降趋势,上午9:30以后全天的P_n值均接近零,非气孔限制成为P_n下降的主要因素; 而对照地枫皮叶片的P_n日变化呈“双峰型”,中午P_n下降的主要原因依然是气孔限制。水分胁迫下,地枫皮叶片叶绿素含量降低和Chl_(a/b)升高,减少了叶片对光能的捕获, 减轻了光合机构遭受光氧化的破坏,而Car/Chl_(a+b)升高增强了光保护能力。水分胁迫下,地枫皮叶片的初始荧光(F_o)显著增大,最大荧光(F_m)、光系统Ⅱ(PSⅡ)潜在活性(F_v/F_o)和最大光化学效率(F_v/F_m)均显著降低,表明水分胁迫对地枫皮叶片的PSⅡ反应中心和电子传递造成了一定的破坏,从而使其PSⅡ的潜在活性和最大光化学效率降低。复水5 d后,地枫皮的上述生理生态参数均能恢复到对照水平,表明其复水后的生理修复能力很强。

Abstract:

In order to understand the eco-physiological adaptability to water stress of karst plant, the experiments were carried out with 4-year-old Illicicum difengpi K. I. B. et K. I. M plants, which was a karst endemic medicinal plant. We investigated the photosynthetic variables, chlorophyll fluorescence variables and photosynthetic pigment content of I. difengpi under water stress and rewatering conditions. The results showed that withholding water for 10 d, the net photosynthetic rate(P_n), intercellular CO₂ concentration(C_i), stomatal limitation value(L_s)and stomatal conductance(G_s)of I. difengpi leaves decreased significantly under water stress, and stomatal limitation was the main reason for the decrease of P_n. Withholding water for 15 d, under water stress, the diurnal variation of P_n showed a gradual downward trend and the P_n values were close to zero after 9:30 am, which suggested that the depression of photosynthesis might be due to non-stomatal limitation. While the diurnal variation of P_n was dual-peaked in the leaves of control, and stomatal limitation was still the main reason for the decrease of P_n. The decrease of chlorophyll content and the increased of Chl _{(a/b )}under water stress conditions, which reduced the binding proteins(LHC Ⅱ)content, the captured light energy, and the risk of photosynthetic apparatus damage. Under water stress condition, the initial fluorescence(F_o)increased significantly, the maximum fluorescence(F_m), potential activity of photo-system Ⅱ(F_v/F_o)and maximal photochemical efficiency of photo-system Ⅱ(F_v/F_m)decreased significantly, which indicating that water stress could cause a certain degree of damage or fracture to its PS Ⅱ reaction center, therefore, the potential activity and maximal photochemical efficiency of PS Ⅱ were reduced. After re-watering for 5 d, the above-mentioned physiological and ecological parameters of I. difengpi could recover to the control level, indicated that the physiological repair capability of which is very strong after rehydration.