Definition of fine roots on the basis of the root anatomy, diameter, and branch orders of one-year old Fraxinus mandshurica seedlings

Abstract

Fine roots are important in root absorption of nutrient and water, and in root turnover. Accurate definition of fine roots is a prerequisite to improved estimation of the physiological and ecological functions of forest ecosystems. Root development and physiological functions are reflections of root anatomical structure. In this study, the anatomical structures of different root orders were analyzed by examining paraffin sections of one-year old Fraxinus mandshurica seedlings. One-year-old F. mandshurica seedlings had over five root orders. The root anatomical structures of all orders showed more differences. First and second order roots consisted of four sections: the epidermis, cortex, pericycle, and vascular bundles. Fourth and fifth order roots were mainly composed of the skin and peripheral vascular bundles (including the xylem and phloem). Third order roots had root epidermal and cortical structures, but the quantity and integrity of the cortical cells were inferior to those of the first and second order roots, and superior to those of the fourth and fifth order roots. All the first and second order roots and some third order roots with discontinuous cork layer (< 0.4 mm in diameter), but not the fourth and fifth order roots, were the fine roots of one-year old F. mandshurica seedlings. Although they had similar diameters, different portions of root systems had different anatomical structures and therefore, vary in capacity to absorb water and nutrients. Fine roots were accurately defined by root diameter, branch orders, and anatomical structural features of one-year old F. mandshurica seedlings.

Keywords

Fine root / Root order / Fraxinus mandshurica / Anatomical structure

References

[1] Aber JD, Melillo JM, Nadelhoffer KJ, Mcclaugherty CA, Pastor J. Fine root turnover in forest ecosystems in relation to quality and form of nitrogen availability: a comparison of two methods. Oecologia, 1985, 66: 317-321.

[2] Donnelly L, Jagodziński AM, Grant OM, O’Reilly C. Above- and below-ground biomass partitioning and fine root morphology in juvenile Sitka spruce clones in monoclonal and polyclonal mixtures. For Ecol Manage, 2016, 373: 17-25.

[3] Eissenstat DM, Achor DS. Anatomical characteristics of roots of citrus rootstocks that vary in specific root length. New Phytol, 1999, 141: 309-321.

[4] Eissenstat DM, Wells CE, Yanai RD, Whitbeck JL. Building roots in a changing environment: implications for root longevity. New Phytol, 2000, 147: 33-42.

[5] Fahey TJ, Hughes JW. Fine root dynamics in a northern hardwood forest ecosystem, Hubbard Brook Experimental Forest, NH. J Ecol, 1994, 82: 533-548.

[6] Fitter AH. Fitter AH, Atkinson D, Read DJ, Usher MB. Functional significance of root morphology and root system architecture. Ecological interaction in soil, 1985, Oxford: Blackwell Scientific Publication 87 106

[7] Gordon WS, Ackson RB. Nutrient concentrations in fine roots. Ecology, 2000, 81: 275-280.

[8] Gu JC, Yang Xu, Dong XY, Wang HF, Wang ZQ. Root diameter variations explained by anatomy and phylogeny of 50 tropical and temperate tree species. Tree Physiol, 2014, 34: 415-425.

[9] Gu JC, Wei X, Wang J, Wang Z. Marked differences in standing biomass, length density, anatomy and physiological activity between white and brown roots in Fraxinus mandshurica Rupr. plantation. Plant Soil, 2015, 392(1–2): 267-277.

[10] Guo DL, Xia M, Wei X, Chang W, Liu Y, Wang Z. Anatomical traits associated with absorption and mycorrhizal colonization are linked to root branch order in twenty-three Chinese temperate tree species. New Phytol, 2008, 180: 673-683.

[11] Hendrick RL, Pregitzer KS. Thedynamics of fine root length, biomass and nitrogen content in two northern hardwoods ecosystems. Can J For Res, 1993, 23: 2507-2520.

[12] Hishi T. Heterogeneity of individual roots within the fine root architecture: causal links between physiological and ecosystem functions. J For Res, 2007, 12: 126-133.

[13] Hishi T, Takeda H. Life cycles of individual roots in fine root system of Chamaecyparis obtusa. J For Res, 2005, 10: 181-187.

[14] Jagodziński AM, Kałucka I. Fine roots biomass and morphology in a chronosequence of young Pinus sylvestris stands growing on a reclaimed lignite mine spoil heap. Dendrobiology, 2010, 64: 19-30.

[15] Jagodziński AM, Kałucka I. Fine root biomass and morphology in an age-sequence of post-agricultural Pinus sylvestris L. stands. Dendrobiology, 2011, 66: 71-84.

[16] Jagodzinski AM, Ziółkowski J, Warnkowska A, Prais H. Tree age effects on fine root biomass and morphology over chronosequences of Fagussylvatica, Quercusrobur and Alnusglutinosa stands. PLoS ONE, 2016 11 2 e0148668

[17] Joslin JD, Henderson GS. Organic matter and nutrients associated with fine root turnover in a white oak stand. For Sci, 1987, 33: 330-346.

[18] King JS, Albaugh TJ, Allen HL, Buford M, Strain BR, Dougherry P. Belowground carbon input to soil is controlled by nutrient availability and fine root dynamics in loblolly pine. New Phytol, 2002, 154: 389-398.

[19] Macfall JS, Johnson GA, Kramer PJ. Comparative water uptake by roots of different ages in seedlings of loblolly pine (Pinus taedaL). New Phytol, 1991, 119: 551-560.

[20] Majdi H. Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden. Tree Physiol, 2001, 21: 1057-1061.

[21] McCormak ML, Dickie IA, Eissenstat DM Redefining fine root improves understanding of below-ground contributions to terrestrial biosphere processes. New Phytol, 2015, 207: 505-518.

[22] McCrady RL, Comerford NB. Morphological and anatomical relationships of loblolly pine fine roots. Trees, 1998, 12: 431-437.

[23] Mckenzie EB, Peterson CA. Root browning in Pinus banksiana Lamb. And Eucalyptus pilularis Sm. 2. Anatomy and permeability of the cork zone. BotanicaActa, 1995, 108: 138-143.

[24] Nadelhoffer KJ, Aber JD, Melillo JM. Fine roots, net primary production, and soil nitrogen availability: a new hypothesis. Ecology, 1985, 63: 1481-1490.

[25] Norby RJ, Jackson RB. Root dynamics and global change: seeking an ecosystem perspective. New Phytol, 2000, 147: 3-12.

[26] Peterson CA, Enstone DE. Functions of passage cells in the endodermis and exodermis of roots. Physiol Plant, 1997, 97: 592-598.

[27] Peterson CA, Enstone DE, Taylor JH. Pine root structure and its potential significance for root function. Plant Soil, 1999, 217: 205-213.

[28] Pregitzer KS, Laskowski MJ, Burton AJ. Variation in sugar maple root respiration with root diameter and soil depth. Tree Physiol, 1998, 18: 665-670.

[29] Pregitzer KS, Deforest JL, Burton AJ, Allen MF, Ruess RW. Fine root architecture of nine North American trees. Ecol Monogr, 2002, 72: 293-309.

[30] Ruess RW, Hendrick RL, Burton AJ, Pregitzer KS, Sveinbjornesson B, Allen MF, Maurer GE. Coupling fine root dynamics with ecosystem carbon cycling in black spruce forests of interior Alaska. Ecol Monogr, 2003, 73: 643-662.

[31] Steudle E, Peterson CA. How does water get through roots?. J Exp Bot, 1998, 49: 775-788.

[32] Taylor JH, Peterson PA. Morphometric analysis of Pinus banksiana Lamb. Root anatomy during a 3-month field study. Trees-Struct Funct, 2000, 14: 239-247.

[33] Tierney GL, Fahey TJ. Fine root turnover in a northern hardwood forest: a direct comparison of the radiocarbon and minirhizotr on methods. Can J For Res, 2002, 32: 1692-1697.

[34] Valenzuela-Estrada LR, Vera-Caraballo V, Ruth LE, Eissenstat DM. Root anatomy, morphology, and longevity among root orders in Vaccinium corymbosum (Ericaceae). Am J Bot, 2008, 95: 1506-1514.

[35] Vogt KA, Persson H. Lassoie JP, Hinckle TM. Measuring growth and development of roots. Techniques and approaches in forest tree ecophysiology, 1991, Boston: CRC Press 477 501

[36] Wang XR, Wang ZQ, Han YZ, Gu JC, Guo DL, Mei L. Variation of fine root diameter with root order in Manchurian ash and Dahurian larch plantation. Acta Phytophysiologica Sinica, 2005, 29: 871-877.

[37] Wells CE, Eissenstat DM. Marked differences in survivorship among apple roots of different diameters. Ecology, 2001, 82: 882-893.

[38] Wells CE, Eissenstat DM. Beyond the roots of young seedlings: the influence of age and order on fine root physiology. J Plant Growth Regula, 2003, 21: 324-334.

[39] Zhang XQ, Wu KH. Fine root production and turnover for forestry ecosystem. Science Silv Sin, 2001, 37: 126-138.