title: Effects of nutrient heterogeneity and competition on root architecture of spruce seedlings: implications for an essential feature of root foraging.
abstract: BACKGROUND
  We have limited understanding of root foraging responses when plants were simultaneously exposed to nutrient heterogeneity and competition, and our goal was to determine whether and how plants integrate information about nutrients and neighbors in root foraging processes.
  
  
  RESULTS
  The experiment was conducted in split-containers, wherein half of the roots of spruce (Picea asperata) seedlings were subjected to intraspecific root competition (the vegetated half), while the other half experienced no competition (the non-vegetated half). Experimental treatments included fertilization in the vegetated half (FV), the non-vegetated half (FNV), and both compartments (F), as well as no fertilization (NF). The root architecture indicators consisted of the number of root tips over the root surface (RTRS), the length percentage of diameter-based fine root subclasses to total fine root (SRLP), and the length percentage of each root order to total fine root (ROLP). The target plants used novel root foraging behaviors under different combinations of neighboring plant and localized fertilization. In addition, the significant increase in the RTRS of 0-0.2 mm fine roots after fertilization of the vegetated half alone and its significant decrease in fertilizer was applied throughout the plant clearly showed that plant root foraging behavior was regulated by local responses coupled with systemic control mechanisms.
  
  
  CONCLUSIONS
  We measured the root foraging ability for woody plants by means of root architecture indicators constructed by the roots possessing essential nutrient uptake ability (i.e., the first three root orders), and provided new evidence that plants integrate multiple forms of environmental information, such as nutrient status and neighboring competitors, in a non-additive manner during the root foraging process. The interplay between the responses of individual root modules (repetitive root units) to localized environmental signals and the systemic control of these responses may well account for the non-additive features of the root foraging process.
authors.affiliation: Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Nan
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.forename: Jinsong
authors.initials: J
authors.lastname: Chen
authors.forename: Xinying
authors.initials: X
authors.lastname: Cheng
authors.forename: Huajun
authors.initials: H
authors.lastname: Yin
authors.forename: Chunying
authors.initials: C
authors.lastname: Yin
authors.forename: Chunzhang
authors.initials: C
authors.lastname: Zhao
mesh_terms: D000222:Adaptation, Physiological; D004777:Environment; D005308:Fertilizers; D028222:Picea / Q000033:anatomy & histology* / Q000502:physiology; D018517:Plant Roots / Q000033:anatomy & histology* / Q000502:physiology; D036226:Seedlings / Q000033:anatomy & histology* / Q000502:physiology; D012987:Soil / Q000737:chemistry
chemical_list: D005308:Fertilizers; D012987:Soil