土壤氮素异质性分布和马先蒿寄生对长芒棒头草生长发育及根系分布的影响

Effects of soil nitrogen heterogeneity and parasitism by Pedicularis species on growth and root spatial distribution of Polypogon monspeliensis

无论在农田还是自然生态系统中,土壤养分异质性普遍存在。植物具有感知土壤养分异质性的能力,并通过调节根系生物量分配及空间分布以获取更多资源。了解寄生胁迫在不同养分条件下对寄主生长发育及根系空间分布的影响,对解析寄主应对寄生胁迫和养分胁迫的适应策略,进而指导寄生性杂草防控具有重要的指导意义。该文采用分根试验,通过对寄主分根,并控制根室两侧氮供应水平及寄生胁迫程度,考察了氮胁迫及两种寄主依赖程度不同的马先蒿的寄生对寄主长芒棒头草生长发育及根系空间分布的影响。结果表明:(1)土壤氮水平与马先蒿寄生均可显著影响长芒棒头草生物量及根冠比,并且两者之间存在显著交互作用,其中土壤氮水平为主要影响因子。(2)两种马先蒿对长芒棒头草的危害程度不同。在NPK和2NPK处理时,三色马先蒿的寄生显著降低长芒棒头草生物量(茎叶:37.1%、51.5%;根系:35.6%、63.6%);在NPK处理时,大王马先蒿的寄生显著增加长芒棒头草生物量(茎叶:29.9%,根系:61.2%)。(3)长芒棒头草的根系生长和空间分布受氮营养的异质分布和寄生的影响,具有明显的感知养分空间分布及调节根系生长能力。

Soil nutrient heterogeneity is ubiquitous in both farmlands and natural ecosystems.Plants have the ability to perceive soil nutrient heterogeneity and adjust biomass allocation to optimize root spatial distribution so as to obtain more resources.As an important nutrient stress,the effects of a root hemiparasite on spatial distribution of its host roots remain untested.Understanding parasitism effects on host growth and root distribution under different nutrient conditions is of great significance for a better knowledge of host adaptation strategies,which will contribute to parasitic weed management.A split-root pot cultivation experiment was conducted to investigate the effects of nitrogen supply levels and parasitism by two root hemiparasitic Pedicularis species on host(Polypogon monspeliensis)growth and biomass allocation to each side of the split roots.The results were as follows:(1)Nitrogen levels and parasitism by Pedicularis species had significant effects on host biomass and root allocation patterns.Significant interaction effects were detected between nitrogen levels and parasitism,with nitrogen levels contributing more to the observed variances.(2)P.tricolor and P.rex showed different effects on host biomass.P.tricolor reduced host shoot biomass by 37.1%and 51.5%,and root biomass by 35.6%and 63.6%,respectively,when supplied with NPK and 2 NPK solutions.However,P.rex significantly increased host shoot biomass by 29.9%and root biomass by 61.2%in NPK treatment and had little effect in 2 NPK treatments.(3)Polypogon monspeliensis roots had obvious perception of nitrogen heterogeneity and parasitism by the root hemiparasites,as shown by foraging behavior for nitrogen and a tendency to avoid Pedicularis roots in treatments with equally low N levels.