水氮耦合对辣木幼苗根系形态特征的影响

Coupling effects of water and nitrogen fertilization on root morphological characteristics of Moringa oleifera seedlings

关键词:  水氮耦合, 根系特征, 施肥, 栽培树种, 热带

Key words:  coupling of water and nitrogen, root traits, fertilization, cultivated species, tropics

摘要:

辣木(Moringa oleifera)主要分布在热带地区,属落叶乔木,具有极高的经济价值和栽培用途。为探究12种水氮组合处理对辣木根系形态的影响,该研究设置3种土壤水分梯度,分别为40%(低水,W1)、60%(中水,W2)、80%(高水,W3)的田间饱和持水量,以及4种氮水平,分别为无氮(N0,0 g·plant^-1)、低氮(N1,0.6 g·plant^-1)、中氮(N2,1.8 g·plant^-1)、高氮(N3,3.6 g·plant^-1),比较不同水氮组合处理对辣木幼苗粗根和细根性状(根长度、根表面积、根体积、根平均直径、比根长、比表面积等)的影响。结果表明:(1)水处理对辣木幼苗粗根和细根的性状没均有显著影响。(2)氮处理对粗根的根长、根表面积、根体积、根平均直径和比表面积有显著影响,而仅对细根的平均直径和比表面积有显著影响。(3)双因素方差分析显示,水氮交互作用仅对细根根长有显著影响; 在相同的水处理下,低氮促进而高氮抑制辣木粗根和细根根长、根表面积和根体积的增加,说明低氮中水处理和低氮高水处理在一定程度上促进根系生长。综上表明,单一水处理的差异并没有显著改变辣木根系特性; 低氮促进而高氮抑制辣木根系的生长且辣木粗根对氮处理的响应更敏感; 水氮耦合对辣木根系生长有明显的调控作用,低氮中水或低氮高水的组合模式更利于辣木根系生长; 为提高速生辣木的生长及生物量的累积,在生产上应严格控制水和氮的使用量及其配比,有效提高水和氮肥的利用效率。

Abstract:

Moringa oleifera is a perennial tropical deciduous tree species, which has high economic value and cultivation purpose. In order to investigate the effects of different water(W)and nitrogen(N)additions on the root growth and traits of M. oleifera, we explored the response of root growth(e.g., root length, surface area, volume and average diameter of coarse and fine roots)of M. oleifera seedlings to the coupling of different soil water and nitrogen availabilities. There were three soil W gradients including 40%(low water, W1), 60%(medium water, W2), 80%(high water, W3)of field saturated water capacity(SWC), and four N application levels, including no notrigen(N0, 0 g·plant^-1), low notrigen(N1, 0.6 g·plant^-1), medium notrigen(N2, 1.8 g·plant^-1), and high notrigen(N3, 3.6 g·plant^-1). The results were as follows:(1)W treatment had no significant effects on the coarse and fine root traits.(2)N treatment significantly affected the coarse root length, surface area, volume, average diameter and specific root area(SRA), while only significantly influenced fine root average diameter and SRA.(3)Two-way ANOVA demonstrated that the interaction between W and N only dramatically affected fine root length; under the same W treatment, low N promoted but high N suppressed the coarse and fine root length, surface area and volume, suggesting that the coupling of N1 with W2, or N1 with W3 to some extent promoted the root growth. The study indicates that single W treatment does not change the root traits, N1 promotes but N3 inhibit the root growth, and the coarse root are more sensitive to N application than fine root thus the coupling of W and N can obviously regulate the root growth of M. oleifera. Therefore, in order to promote the growth and biomass accumulation of M. oleifera, usage and coupling percentage of water and nitrogen should be restrained and effectively enhance the water and nitrogen efficiency in practices.