摘要:根腐病是严重威胁三七生产的重要因素之一，常年发病率在5%~20%。其中，由假单胞杆菌（Pseudomon adaceae）引起的细菌性根腐病，因叶片出现缺水萎蔫症状时才能发现，目前尚无有效的预防措施。为探究细菌性根腐病对三七光合生理特性的影响，从而为三七病害生理学研究提供理论基础，本文以2年生三七为材料，设置2个处理[发病植株和健康对照植株（CK）]，研究细菌性根腐病对三七形态结构、光合特性和光系统功能的影响。结果表明：1）根腐病导致三七的主根褐变腐烂，须根断损，茎基部腐烂中空，叶片萎蔫，各器官含水量比CK显著降低（P≤0.05）；而株高、叶面积和叶片解剖结构（上表皮厚度、下表皮厚度、栅栏组织厚度和海绵组织厚度）在两处理间均无显著差异。2）发病植株叶片叶绿素含量、净光合速率（Pn）、气孔导度（Gs）、水分利用效率（WUE）和表观叶肉导度（AMC）显著低于CK（P≤0.05），且CK叶片胞间CO2浓度（Ci）与Pn呈反比。3）发病植株叶片的光系统Ⅰ（PSⅠ）反应中心P700最大荧光信号（Pm）根腐病初期暂不受影响，而叶片暗适应下最大量子效率（Fv/Fm）、光系统Ⅱ（PSⅡ）电子传递速率[ETR（Ⅱ）]、PSⅡ实际光化学量子产量[Y（Ⅱ）]、PSⅠ电子传递速率[ETR（Ⅰ）]、PSⅠ周围的环式电子流（CEF）和PSⅠ实际光化学量子产量[Y（Ⅰ）]均显著低于CK（P≤0.05）；参与调节性能量耗散的量子产量[Y（NO）]则显著高于CK（P≤0.05）；发病植株的快速叶绿素荧光动力学曲线上出现K相，且显著高于CK（P≤0.05）。总的来看，细菌性根腐病对三七发病植株各器官的损伤严重程度为根>茎>叶，且根腐病导致发病植株叶片叶绿素降解，PSⅡ受到不可逆损伤，PSⅠ的电子传递被抑制，且叶肉细胞CO2的同化能力降低，根腐病限制三七正常进行光合作用的条件。
关键词:三七/
细菌性根腐病/
缺水/
叶片解剖结构/
光合特性/
叶绿素荧光
Abstract:Root rot is an important factor that has threatened the cultivation of Panax notoginseng, with an incidence rate of 5% to 20%. Bacterial root rot caused by Pseudomon adaceaecan might only be discovered after infected leaves have wilted, and by then there will no longer be any effective control measures. The objective of this study was to explore the differences in effects of bacterial root rot on the photosynthetic physiological characteristics between control (CK) and diseased plants (DP), thus providing a theoretical basis for the understanding of disease physiology in P. notoginseng. The results showed that the taproot of DP was browned and rotted from root rot, accompanied by broken fibrous roots, decay and hollow stems, withering leaves, and low water content. There was no significant difference in plant height, leaf area, and thickness of leaf antomical strucutres (including thickness of upper epidermis, lower epidermis, palisade tissue, and sponge tissue) between DP and CK. However, the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), instantaneous water use efficiency (WUEinst), intrinsic water use efficiency (WUEi), and apparent mesophyll conductance (AMC) were significantly lower in DP than in CK (P ≤ 0.05), with intercellular CO2 concentration (Ci) inversely proportional to Pn in DP individuals. The maximum fluorescence signal of the P700 reaction center (Pm) in DP was not affected during the period of initial infection, but the maximum quantum efficiency of photosystem Ⅱ (PSⅡ) under dark adaptation (Fv/Fm), electron transfer rate of PSⅡ[ETR(Ⅱ)], actual photochemical quantum yields of PSⅡ[Y(Ⅱ)], electron transfer rate of PSⅠ[ETR(Ⅰ)], cyclic electron flow around PSI (CEF), and actual photochemical quantum yields of PSⅠ[Y(Ⅰ)] were significantly lower in DP than in CK (P ≤ 0.05). Additionally, the fraction of energy passively dissipated in the forms of heat and fluorescence[Y(NO)] were significantly higher in DP than in CK (P ≤ 0.05). Furthermore, The K phase in the fast chlorophyll fluorescence kinetic curves was significantly higher in DP than in CK (P ≤ 0.05). Overall, the degree of damage for the various organs of DP was:root>stem>leaf. Root rot significantly degraded leaf chlorophyll, along with irreversible damage to PSⅡ and inhibition of PSⅠelectron transfer and reduced the assimilation ability of mesophyll cells, consequently restricting photosynthetic performance.
Key words:Panax notoginseng/
Bacterial root rot/
Water shortage/
Leaf anatomical structure/
Photosynthetic characteristics/
Chlorophyll fluorescence
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