Growth of tree roots in hostile soil: A comparison of root growth pressures of tree seedlings with peas

• Published in: Plant and soil Vol. 368; no. 1/2; pp. 569 - 580
• Main Authors: Azam, Gausul, Grant, Cameron D., Misra, Rabindra K., Murray, Robert S., Nuberg, Ian K.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01-07-2013; Springer Netherlands; Springer Nature B.V
• Subjects: Acacia; Agricultural soils; Agrology; Agronomy. Soil science and plant productions; Analysis; Animal, plant and microbial ecology; Arid soils; Biological and medical sciences; Biomedical and Life Sciences; Climatic conditions; Crop production; Ecology; Evolution; Food quality; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Growth; Life Sciences; Magnesium; Peas; Pisum sativum; Plant growth; Plant Physiology; Plant roots; Plant Sciences; Plant species; Plants; Regular Article; Root growth; Roots; Sandy loam soils; Seedlings; Soil fertility; Soil science; Soil Science & Conservation; Soil types; Soil water; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Trees; Hard soil; Root growth force; Root elongation; Woody perennials; Acacia; Annual crops; Plant evolution; Eucalypt; Growth; Plant juvenile growth stage; Perennial plant; Eucalyptus; Hard soils; Dicotyledones; Angiospermae; Myrtaceae; High protein crop; Evolution; Developmental stage; C3-Type; Elongation; Vegetals; Root; Annual plant; Woody plant; Pea; Pressure; Grain legume; Leguminosae; Pisum sativum; Vegetative apparatus; Spermatophyta; Soil plant relation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-012-1537-4

Background and Aims As part of a study on growth of tree roots in hostile soil, we envisaged that establishment and survival of trees on hard, dry soil may depend on their ability to exert axial root growth pressures of similar magnitude to those of the roots of agricultural plants (with significant root thickening when roots grow across an air gap or cracks and biopores). We selected tree species originating from a range of different soil and climatic conditions to evaluate whether their relative success on harsh soil (in an evolutionary sense) might be related to the magnitude of root growth pressures they could exert, or how they performed in the very early stages of growth after germination.
Methods We measured the maximum axial root growth force (F
max
) on single lateral root axes of 3- to 4- month old seedlings of 6 small-seeded eucalypts from 2 different habitats and 2 contrasting soil types. Root growth rate, root diameter and F
max
were also measured on the primary root axes of a large-seeded acacia and a domesticated annual (Pisum sativum) seedling for up to 10 days following germination.
Results The lateral roots of the 6 eucalypts and the primary roots of the acacia were considerably smaller than the primary roots of P. sativum and they exerted average forces of similar magnitude to one another (0.198 to 0.312 N). The maximum axial root growth pressures were all in the range 150 to 250 kPa but E. leucoxylon, E. loxophleba and A. salicina exerted the greatest pressures among the trees, and comparable pressures to those exerted by the primary roots of 2-day-old P. sativum (211-252 kPa). Although the primary roots of acacia seedlings exerted increasing axial root growth pressures over a 10-day period following germination, the pressures were still only slightly greater than those of the domesticated plant, P. sativum. Conclusions The lack of any very large differences in axial root growth pressures between trees and domesticated plants suggests that trees that grow well in harsh soil don't do so by exerting higher root growth pressures alone but by also exploring the network of cracks and pores more effectively than do other plants that are less successful.