以8年生落基山圆柏(Juniperus scopulorum)的嫩枝为试验材料, 采用不同扦插密度和基质等处理措施, 研究了微域环境因子对插穗生根的影响。结果表明, 两种不同扦插密度的生根部位、愈伤率、生根率、炼存率、生根效果指数(root effect index, REI)、离散度指数(rooting dispersion index, RDI)和分形特征均存在显著差异。综合分析生根率、炼存率、REI和RDI等发现, 密插处理的效果好于稀插, 稀插处理的插穗生根能力较差, 生根性状离散度较大。密插处理的插穗的根系平均分形维数是稀插处理的1.24倍, 两者差异极显著(p < 0.01)。不同扦插密度下插穗的生根部位和生根机制不同: 插穗在密插处理下形成诱生根, 在稀插处理下形成原基根。不同的扦插密度造成了落基山圆柏微域环境的显著差异, 但同一密度下不同基质种类对微域环境因子的调控作用有限。密插处理下插穗的微域环境相对湿度较高(最高可达83.5%), 温度较低, 光合有效辐射较小。这些环境因子的差异导致密插处理下插穗的净光合速率(P_n)较高, 蒸腾速率(T_r)较低。在0-60天内, 密插和稀插处理的插穗的P_n均呈上升趋势, 并且二者相差的幅度随着试验时间的延长而迅速增大; 在60天以后, 二者均呈下降趋势, 相差幅度基本保持不变。密插处理下的T_r值在0-30天内基本保持不变, 而此时稀插处理下的T_r迅速增加。在30-60天内密插处理下的T_r快速增加, 60天时达到最大值, 但仍低于稀插处理。这些结果表明, 外部微域环境因子对插穗生根的影响是通过影响其内在生理指标来实现的, 插穗营养状况的差异是造成生根机制不同的主要原因。

Aims Microenvironmental factors such as relative humidity, temperature and light intensity have significant effects on rooting. Our objective was to study the impact of microenvironmental factors on rooting of cuttings of Juniperus scopulorum (Rocky Mountain juniper), a native of western North America.
Methods We used the softwood of eight-year-old J. scopulorum in a split plot experiment with five plots in river sand and peat substrates and two subplots in each plot with different cutting densities of 400 cuttings·m^-2 (thin) and 1 666 cuttings·m^-2 (dense). Data were analyzed using SPSS software.
Important findings The rooting site, rate of callus-formation, rooting percentage, survival rate after training, root effect index (REI), rooting dispersion index (RDI) and fractal feature of J. scopulorum cuttings in the two densities were significantly different. Analysis of rooting percentage, survival rate after training, REI and RDI indicated that the integrated effect in dense cuttings was better than thin cuttings. The rooting ability of thin density cuttings was worse, but degree of rooting dispersion was higher. The average rooting fractal dimension of dense cuttings was significantly 1.24 times higher than of thin cuttings, and dense cuttings had changed rooting position and mechanism. Cuttings often produced induced roots in dense cuttings and primordial roots in thin cuttings. Different cutting densities resulted in significant different microenvironments of cuttings, whereas the regulating effect of different media in same density on microenvironment was limited. The microenvironmental humidity of dense cuttings was higher (up to 83.5%), while temperature and photosynthetically active radiation (PAR) were lower, leading to higher net photosynthetic rate (P_n) and lower transpiration rate (T_r). Within 60 days after insertion, P_n of cuttings in both dense and thin cuttings were rising, and the difference between them increased quickly with time. After 60 days, both were declining, and the difference between them remained relatively constant. Transpiration rate of dense cuttings remained relatively unchanged from 0 to 30 days, while T_r in thin cuttings displayed a rapid increase during the same periods. Transpiration rate of dense cuttings rose sharply in 30-60 days and peaked on the 60th day, but it was still lower than in thin cuttings. These results implied that the effect of microenvironmental factors on rooting of J. scopulorum cuttings was achieved by influencing physiological indexes and that disparity of nutriment status in the two cutting densities was a major cause of differences in the rooting mechanism.