楸树嫩枝扦插生根发育及根系特征分析

【目的】楸树大多自花不育,苗木主要通过营养繁殖获得,而高质量楸树苗木缺乏,扦插育苗存在繁殖系数低、质量参差不一等问题,影响了楸树的大面积推广利用。笔者探索不同处理方式下楸树嫩枝生根及不定根形成特点,初步筛选合适的楸树嫩枝生根方法,为揭示楸树嫩枝扦插生根机理并解决楸树扦插困难提供参考。【方法】以楸树品种‘8611’为试验材料,采用两因素(生根剂类型、枝条部位)完全随机试验,观察插穗在扦插生根过程中的动态变化并进行生根阶段划分;采用石蜡切片法,对不同生根阶段的插穗进行解剖结构分析;利用根系扫描仪测定根系的相关指标,并对各指标数据进行相关性分析和多重比较,得出楸树最优生根处理,明确楸树生根类型及时间。【结果】楸树扦插生根过程可以分为4个阶段:扦插3~7 d为愈伤组织的形成阶段;扦插7~18 d为不定根的诱导阶段;扦插18~20 d为不定根的发生阶段;扦插20 d以后为不定根的伸长阶段。不同生根剂及枝条不同部位的插穗对嫩枝扦插生根存在明显影响。穗条在不同部位间,枝条上部的插穗最易生根,但易腐烂;枝条中部制成的插穗生根效果最佳。不同激素处理中,GGR-6处理的插穗最易生根,生根效果最佳。在不同激素处理下枝条不同部位的生根率表现为:1 000 mg/kg GGR-6处理的中部插穗生根效果最佳,生根率约92%。在形态解剖学观察中,未发现楸树‘8611’种存在潜伏根原基。【结论】楸树嫩枝扦插的生根时间约20 d,为诱导生根类型。采用嫩枝中部制成的插穗,通过1 000 mg/kg GGR-6处理时生根效果最佳。

Dynamic characteristics of cutting rooting of Catalpa bungei with tender branches

【Objective】Catalpa bungei is a precious wood tree species in China. Most C. bugein trees are self-sterile and their seedlings are mainly obtained through vegetative propagation. However, a low propagation coefficient and lack of high-quality cutting seedlings have restrained the development of C. bungei plantation. In order to explore the mechanism of C. bungei rooting and to select a suitable method for cutting rooting of C. bungei, the characteristics of root and principles of adventitious root formation were studied using different treatment methods.【Method】Using variety ‘8611’ of C. bungei as materials, a two factor (rooting agent, branch position) completely randomized design experiment was conducted in this study. The dynamic changes of cuttings and rooting stages were observed and divided during the process of rooting, and then the anatomical structure of cuttings at different rooting stages was analyzed using the paraffin section method. Finally, the related indexes of root system were measured using a root scanner and the correlation analysis and multiple comparison of various index data were carried out to obtain the best root handle.【Result】The rooting process of C. bungei cuttings was divided into four stages: 3-7 days as a callus induction period; 7-18 days as a callus and adventitious roots formation stage; 18-20 days as a large-scale form of adventitious roots of cutting stage; and after 20 days as an adventitious roots elongation period. Different hormones and branch positions had significant effects on shoot rooting. Cuttings made from the upper position of branches easily took root, but were perishable; however, cuttings from the middle position of branches had the best rooting effectiveness. The cuttings treated with GGR-6 were easier in taking root and had the best root formation. Comprehensively, the best treatment was that of the cuttings from the middle position of branches with 1 000 mg/kg GGR-6, in which the rooting rate was approximately 92%. No latent root primordium was found based on morphological and anatomical observations and it is speculated that variety ‘8611’ belongs to the induced root primordium type.【Conclusion】The rooting time of C. bungei was about 20 days, which is likely to be the time of induced rooting. The optimal treatment for cutting rooting of C. bungei was the middle position of the tender branches treated with 1 000 mg/kg GGR-6.