低磷胁迫下杉木无性系根系形态及养分利用响应研究

【目的】研究不同杉木无性系苗木在低磷胁迫下的根系形态和养分利用特征,为提高杉木养分利用效率的遗传改良提供参考。【方法】以5个杉木无性系组培苗为材料,采用土壤盆栽实验,设置缺磷(PO, KH₂PO₄ 0 mmol/L)和正常供磷(PN, KH₂PO₄ 1.0 mmol/L)两种改良Hoagland营养液进行浇灌处理,培养60 d后测定其生物量(根、茎、叶)、根系形态参数及其养分(磷、氮、钾、钙、镁)累积量和利用效率。【结果】①随施磷水平的变化,杉木无性系的干物质质量和根系形态指标显示出极显著的基因型效应差异。②缺磷处理使杉木无性系的根、茎、叶和整株干物质质量分别减少20.06%、20.68%、14.07%和16.78%,根冠比则增加,总根长、总根表面积、总根体积分别增加17.31%、17.69%、24.77%,根平均直径减少8.22%,细根比例显著提高。③缺磷使杉木无性系整株磷累积量减少17.91%,而磷利用效率呈上升趋势,同时磷在根系中的含量降低16.35%,但茎、叶中的含量在处理间差异不显著; 缺磷还使整株对钾的累积量减少27.58%,钙和氮分别减少18.56%和14.95%,镁减少12.85%。④经主成分分析发现,杉木无性系植株的粗根长、细根长、根冠比、根干物质质量与低磷胁迫响应密切; 回归分析显示,细根量对植株的磷吸收量有显著正向效应。【结论】杉木无性系根系形态指标随施磷水平变化呈极显著的基因型效应差异,缺磷胁迫使苗木地上部干物质质量减少,根平均直径减少,细根比例增大,根冠比增大,根系趋向于磷高效吸收的根构型转变,进而提高对低磷胁迫的遗传适应性。

Response of roots morphological characteristics and nutrient utilization to low phosphorus stress among five clones of Cunninghamia lanceolate(Lamb.)Hook.

【Objective】 In this study, the roots architecture of Chinese fir(Cunninghamia lanceolate(Lamb.))under low phosphorus stress was explored in order to provide the scientific basis for improving nutrient use efficiency through the genetic improvement of root plasticity.【Method】 Five Chinese fir clones, propagated by tissue culture, were used for pot culture and irrigated with half-strength Hoagland nutrient solution with different KH₂PO₄(P)supplying levels(low P stress(PO), 0 mmol/L; suitable P(PN), 1.0 mmol/L). The biomass of the root, stem and leaf, as well as the root morphological indices and nutrient(P, N, K, Ca and Mg)accumulation and utilization efficiency were measured for plants of each clone after 60 d of culture.【Result】 ①The biomass and root morphological indices had significant genotypic effects with the change in P application level. ②Compared to plants under suitable P conditions, the biomass of the root, stem, leaf and whole plant were reduced by 20.06%, 20.68%, 14.07% and 16.78%, respectively, while the ratio of root to shoot showed an increasing trend. The total root length, total root surface area, and total root volume was increased by 17.31%, 17.69% and 24.77%, respectively. The average root diameter was decreased by 8.22% under low P stress. ③When supplying with an insufficient P solution, plant P accumulation and P content in the roots were reduced by 17.91% and 16.35%, respectively, there was no significant influence on P contents in the stem and leaf. Meanwhile, with the decrease of P accumulation, the use efficiency of P increased. Under insufficient P treatment, the accumulation of potassium, calcium, nitrogen and magnesium was reduced by 27.58%, 18.56%, 14.95% and 12.85%, respectively. ④Principal component analysis showed that root length, fine root length, ratio of root to shoot, and root dry weight were important morphological indices to low P stress. The result of analysis of regression showed that fine roots had a positive effect on P uptake.【Conclusion】 Chinese fir clones adapted to low P stress through the changes in root architecture, including reducing biomass accumulations of the stem and leaf, as well as the root diameter, and increasing the proportion of fine roots, prompting an increase in the ratio of root to shoot, and increasing the construction efficiency of roots.