外源信号物质对檀香幼苗生长和光合特性的影响

【目的】根系分泌物在植物种间关系中发挥着重要作用。研究根系分泌物及一些根系常见的化学物质对半寄生檀香生长、根系发育、养分吸收和光合特性的影响,筛选出促进檀香幼苗生长的寄主根系分泌物或化学物质,为檀香的科学育苗提供参考。【方法】 选取0.5年生的半同胞家系檀香幼苗为试验材料,设置10个外源信号物质处理,包括5种植物根系分泌物寄主植物降香黄檀(Dalbergia odorifera)、台湾相思(Acacia confusa)、人面子(Dracontomelon duperrereanum)、重阳木(Bischofia polycarpa)和寄生植物檀香(Santalum album)]、4种吸器诱导物质2,6-二甲氧基对苯醌 (DMBQ)、芒柄花素、槲皮素和丁香醛]和1个对照处理(水),处理3个月后测定檀香幼苗的生长指标(株高、地径、生物量)、根系形态(总根长、根表面积)、养分(N、P、K)含量和光合特性指标叶绿素相对含量(SPAD)净光合速率、气孔导度、蒸腾速率]等。【结果】 外源信号物质能影响檀香幼苗的生理特性,降香黄檀根系分泌物、DMBQ和丁香醛处理能显著提高檀香幼苗的株高、地上与地下生物量;除重阳木外,其他植物根系分泌物和4种化学物质处理均显著增加了檀香幼苗的总根长、根表面积和小细根长度;与对照相比,外源信号物质均提高了檀香幼苗N、P、K等养分吸收能力,其中以DMBQ和降香黄檀根系分泌物处理效果最佳;降香黄檀和台湾相思根系分泌物、DMBQ及丁香醛处理均显著提高了檀香叶片的SPAD值;降香黄檀根系分泌物和4种化学物质处理显著提高了檀香幼苗的光合自养能力;相关性分析显示,檀香生长指标、生理指标与根系之间(粗细根、粗根长度除外)呈显著正相关;檀香吸器数与总根长、根表面积呈极显著正相关关系,说明檀香吸器发育与根系生长密切相关。【结论】 优良寄主植物根系分泌物及一些化学物质的添加能有效促进檀香幼苗根系发育、养分吸收以及光合能力。研究结果能为檀香的壮苗培育提供重要的实践指导。

Effects of exogenous signal substances on growth and photosynthetic characteristics of Santalum album seedlings

【Objective】Root exudates play an important role in the plant interspecific relationship. The effects of host root exudates and chemicals on growth, root development, nutrient accumulation and photosynthetic characteristics of hemiparasitie Santalum album seedlings were studied. The superior host root exudates or several chemicals were screened to provide a scientific guidance for cultivating S. album seedlings.【Method】Under greenhouse conditions, we performed the pot experiment to determine whether root exudates (Acacia confusa, Bischofia polycarpa, Dalbergia odorifera, Dracontomelon duperrereanum and S. album) and haustorium-inducing chemicals (2,6-dimethoxy-p-benzoquinone (DMBQ), formononetin, quercetin and syringaldehyde) could promote the growth and root development of S. album seedlings. The growth indices (height, diameter and biomass), root morphology (total root length and root surface area), nutrient (N, P, K) contents, and photosynthetic characteristics (SPAD values, photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r)) of S. album seedlings were measured after a 3-month treatment.【Result】The height, shoot and root biomass of S. album seedlings exhibited the significantly greater growth when treated with Dalbergia odorifera root exudates, DMBQ and syringaldehyde. The total root length, root surface area and length of thin fine roots were significantly greater in S. album seedlings treated with 4 root exudates (except for B. polycarpa) and 4 chemicals than those of the control treatment. The exogenous signal substance could promote N, P and K absorption of S. album seedlings, especially for Dalbergia odorifera root exudate and DMBQ. Root exudates of Dalbergia odorifera and A. confusa, DMBQ and syringaldehyde induced significantly higher SPAD values. Dalbergia odorifera root exudate and 4 chemicals could induce significantly higher photosynthetic characteristics of S. album seedlings. The correlation analysis shows that there are significant and strong correlations between growth indices, physiology indices and root growth (except for thick fine root and coarse root length). Haustoria number of S. album seedlings are significantly correlated with the total the root length and root surface area, indicating that the haustorium development of S. album is closely related to root growth.【Conclusion】The application of root exudates of superior host and/or haustorium-inducing chemicals could effectively promote root development, nutrient absorption, and photoautotrophic capability of S. album seedlings. Our results provide insights into S. album nursery in south China.