【目的】了解木槿扦插生根机制,探索植物生长调节剂萘乙酸(NAA)和吲哚丁酸(IBA)对木槿嫩枝扦插的影响,筛选提高木槿扦插成活的配方,为木槿扦插繁殖提供参考。【方法】以木槿1年生嫩枝为试验材料,采用3种质量浓度(100、300、600 mg/L)的NAA和IBA溶液处理插穗,以清水为对照(CK)进行完全随机区组扦插试验,对插穗解剖结构、生根性状和叶片生理指标进行观测,测定了插穗的生根率(RR)、根鲜质量(RFW)、根系TTC还原强度(RA)、TTC还原总量(TTC_RA)、平均根长(ARL)、根平均直径(RAD)、根表面积(SA)、根体积(RV)、根尖数(RT)、根长密度(RLD)、比根长(SRL)、叶绿素含量(Chl)和净光合速率(P_n)等。【结果】①显微观察发现,木槿不定根原基最先由位于插穗形成层和髓射线结合点处钝圆锥形的薄壁细胞群分裂分化而成,不定根发生后通过皮孔向外伸出;②与CK相比,300 mg/L的IBA处理下,木槿插穗的生根性状和生理指标中RR、RFW、RA、TTC_RA、ARL、RAD、SA、RV、RT和RLD分别增加了554%、527%、58%、892%、198%、50%、282%、457%、126%、198%,而SRL、Chl和P_n分别降低了52%、51%和82%;③相关性分析发现,木槿插穗叶片Chl、P_n与大部分根系指标呈负相关;④通过隶属函数法对各处理生根能力评价可知,IBA处理下插穗生根能力比NAA处理的高,300 mg/L的 IBA处理下生根能力最强。【结论】木槿插穗以皮部生根为主;木槿插穗生根过程中地上部分生长与地下部分生根存在竞争关系,两种植物生长调节剂能够促进木槿插穗地下部分生根,抑制地上部分生理性状;植物生长调节剂具有浓度阈值效应,300 mg/L IBA处理是促进木槿扦插生根最适宜的配方。

【Objective】The aim of this study was to understand the rooting mechanism of Hibiscus syriacus cuttings, including the relevant effects of two plant growth regulators and their suitable formula, as well as to improve the rooting rate and provide a theoretical support for the propagation of H. syriacus cuttings. 【Method】One-year-old branches of H. syriacus seedlings were collected as experimental materials. A completely randomized block design with two factors, including two plant growth regulators (naphthylacetic acid, NAA; indolebutyric acid, IBA) at three concentrations (100, 300 and 600 mg/L), were used. One water-treated sample was used as a control (CK). The anatomical structure, rooting growth characteristics, and leaf physiological characteristics of H. syriacus cuttings were measured during the rooting process using a UY203i biological fluorescence microscope, a STD4800 scanner calibrated for an image analysis with WinRHIZO software, a JA5003N one-thousandth electronic balance, a STYS-1 plant chlorophyll measuring instrument in vivo, and a FS-3080H photosynthesis system. The measured indexes included the rooting rate (RR), root fresh weight (RFW), root TTC reducing ability (RA), root TTC reducing amount (TTC_RA), average root length (ARL), root average diameter (RAD), root surface area (SA), root volume (RV), root tip number(RT), root length density (RLD), specific root length (SRL), chlorophyll content (Chl) and net photosynthetic rate (P_n) in the rooting process. 【Result】① It was found by microscopic observation that the adventitious root primordium of H. syriacus cuttings originated from a group of parenchyma cells with a blunt conical shape located in the cross region of pith rays and vascular cambium. The adventitious root primordia developed into young adventitious roots and then extended outward through the lenticels. ② Compared with the control (CK), the rooting rate (RR), root fresh weight (RFW), root TTC reducing ability (RA), root TTC reducing amount (TTC_RA), average root length (ARL), root average diameter (RAD), root surface area (SA), root volume (RV), root tip number (RT), and root length density (RLD) of 300 mg/L IBA treatment increased by 554%, 527%, 58%, 892%, 198%, 50%, 282%, 457%, 126% and 198%, respectively, and its specific root length (SRL), chlorophyll content (Chl), and net photosynthetic rate (P_n) were reduced by 52%, 51% and 82%, respectively. ③ According to the correlation analysis, the Chl and P_n of H. syriacus seedlings had a negative relationship with most of the root indicators. Chl was significantly negatively correlated with SA and very significantly negatively correlated with ARL and RLD. P_n was very significantly negatively correlated with RA and significantly negatively correlated with ARL and RLD. ④ Using the subordinate function value method that the rooting ability of the IBA treatment exceeded that of the NAA treatment, and the rooting ability of the 300 mg/L IBA treatment was the best. 【Conclusion】 The cortex rooting type was the main type of rooting found in H. syriacus cuttings. There was a competitive relationship between the overground parts and the underground parts of H. syriacus cuttings during the rooting process. Two plant growth regulators could promote rooting of H. syriacus cuttings and inhibit the physiological characteristics of its overground parts. The treatment with 300 mg/L IBA provided the most suitable formula.