不同基因型棉花根系对局部供磷的响应特征

Root response of different cotton genotypes to local phosphorus supply

【目的】养分异质性存在于自然土壤或农田土壤,探讨不同基因型棉花根系对异质性养分的响应,对提高棉花磷利用效率具有重要意义。【方法】本试验在土培条件下,设磷均质供应和磷局部供应两种供磷方式,根箱自上而下分为三层(上层0—20 cm、中层20—40 cm、下层40—60 cm)。磷均质供应方式下根箱每一层的磷肥用量均为P_2O_5 100 mg/kg,磷局部供应方式下磷肥用量为P_2O_5 300 mg/kg,全部集中施在中层(20—40 cm),上下两层均不施磷,两种供磷方式下氮钾肥均按N 150 mg/kg和K2O 5 mg/kg均匀加入至根箱各层(施钾量按75k g/h m 2计算),利用根箱分层研究2种基因型棉花根系对局部供磷(2 0—4 0c m)响应的差异。【结果】局部供磷能显著改变棉花的根系形态,磷低效基因型‘新陆早13号’和磷高效基因型‘新陆早19号’总根长、根系表面积、根系总体积、比根长、中层细根长度分别增加了38.0%、41.9%、97.6%、27.3%、35.9%和34.5%、21.7%、39.0%、22.5%、42.8%。棉花对局部供磷的响应存在基因型差异,磷高效基因型‘新陆早19号’的总根长、根系表面积、根系总体积、比根长、中层细根长度均显著高于磷低效基因型‘新陆早13号’,分别是磷低效基因型‘新陆早13号’的1.23、1.31、1.73、1.07、1.30倍。主成分分析表明,棉花根系的可塑性主要受养分供应方式影响,而根系的基本构架主要受基因型控制。偏最小二乘回归分析表明,总根长、中层(20—40 cm)细根(0—0.4 mm)长度、根系表面积和根系总体积的VIP值超过1,对地上磷吸收起着明显重要的作用,其中中层(20—40 cm)细根(0—0.4 mm)长度10%的增加量可以引起地上部磷吸收2.33%的增加,即中层(20—40 cm)细根(0—0.4 mm)长度对植株磷吸收的贡献最大。【结论】在局部供磷区,磷高效基因型棉花具有更高的环境适应能力。对于高效和低效基因型,都应采取局部供磷的方式,优化根系分布和生长,提高棉花获取异质性磷养分的能力,以发挥棉花的最大生物学潜力,提高养分利用率,减少肥料用量,保护生态环境。

【Objectives】In soil,nutrients are distributed in a heterogeneous or patchy manner.It is of great significance to explore response of roots of different cotton genotypes to the heterogeneity of nutrients,which is of great importance to improve phosphorus(P)utilization efficiency of cotton.【Methods】In this soil culture experiment,two kinds of phosphorus supply methods are used:uniform phosphorus supply and local phosphorus supply.The root box is divided into three layers from top to bottom(upper layer 0–20 cm,middle layer 20–40 cm,lower layer 40–60 cm).The amount of phosphorus fertilizer in each layer of the root box is P2O5 100 mg/kg under the uniform phosphorus supply.Phosphorus fertilizer dosage is P2O5 300 mg/kg under local phosphorus supply,all concentrated in the middle layer(20–40 cm),and no phosphorus is applied to the upper and lower layers.Nitrogen and potassium fertilizers are uniformly added to each layer of the root box according to N 150 mg/kg and K2O 5 mg/kg under both phosphorus supply methods(calculated at 75 kg/hm2 of Xinjiang potassium fertilizer),a soil box experiment simulated the localized supplies of P(20–40 cm)is conducted to study root response to local P supply in two cotton genotypes.【Results】Local P supply significantly modified root morphological parameters in two cotton genotypes.Total root length,root surface,root volume,specific root length,fine root length of low phosphorus efficiency genotype(XLZ13)and high phosphorus efficiency genotype(XLZ19)in the local P supply treatment were increased by 38.0%,41.9%,97.6%,27.3%,35.9%and 34.5%,21.7%,39.0%,22.5%and 42.8%,respectively.There were significant differences in root parameters of the two cotton genotypes with the local P supply.The total root length,root surface,root volume,specific root length and fine root length in middle layer of the high phosphorus efficiency genotype(XLZ19)were 1.23,1.31,1.73,1.07 and 1.30-folds of those of the low phosphorus efficiency genotype(XLZ13).The results of the principal component analysis showed that P supply could affect the plasticity of cotton root system,while cotton genotype could modify basic structure of root system.Partial least squares regressive analysis showed that the VIP values of total root length,fine root(0–0.4 mm)length in middle layer(20–40 cm),root surface and root volume were larger than 1,which played important role in aboveground phosphorus uptake.The fine root(0–0.4 mm)length in middle layer(20–40 cm)made greater contribution to P uptake of cotton in soil,i.e,the increase of 10%of fine root(0–0.4 mm)length in middle layer(20–40 cm)could improve 2.33%of the aboveground phosphorus uptake.【Conclusions】The high phosphorus efficiency genotype cotton has higher environmental adaptability in the local P supply.For efficient and inefficient genotypes,the local P supply should be adopted to optimize root distribution and growth,and to improve cotton’s ability to obtain heterogeneous phosphorus nutrients so as to exert the maximum biological potential of cotton,improve nutrient utilization,reduce fertilizer dosage,and protect ecological environment.