Patterns of variability in the diameter of lateral roots in the banana root system

Abstract

Summary• The relative importance of root system structure, plant carbon status and soil environment in the determination of lateral root diameter remains unclear, and was investigated in this study.• Banana ( Musa acuminata ) plants were grown at various moderate levels of soil compaction in two distinct experiments, in a field experiment (FE) and in a glasshouse experiment (GE). Radiant flux density was 5 times lower in GE. The distribution of root diameter was measured for several root branching orders.• Root diameters ranged between 0.09 and 0.52 mm for secondary roots and between 0.06 and 0.27 mm for tertiary roots. A relationship was found between the diameter of the parent bearing root and the median diameter of its laterals, which appears to be valid for a wide range of species. Mean lateral root diameter increased with distance to the base of the root and decreased with branching density [number of lateral roots per unit length of bearing root (cm − 1 )].• Typical symptoms of low light availability were observed in GE. In this case, lateral root diameter variability was reduced. Although primary root growth was affected by soil compaction, no effects on lateral root diameter were observed.

Relationships between root diameter, root length and root branching along lateral roots in adult, field-grown maize

“…The relationships between diameter, length and branching density and their hierarchical connections are discussed below. The positive correlation between daughter root diameter and mother root diameter has been already noted and quantified for several species (Bouma et al, 2001;Lecompte et al, 2005;Bécel et al, 2012;Pagès et al, 2013Pagès et al, , 2014. However, in these studies the sampling methods and definitions of daughter root and bearing root diameter were mostly different from those used here.…”

“…However, in these studies the sampling methods and definitions of daughter root and bearing root diameter were mostly different from those used here. The earlier studies normally linked the median apical diameter of the daughter roots in a whole or a distal bearing root to the apical or average diameter of the bearing root for various dicotyledonous and monocotyledonous species (Lecompte et al, 2005;Bécel et al, 2012;Pagès et al, 2013Pagès et al, , 2014. To account for the change in diameter along the bearing roots, which were not considered in previous studies, we linked the median basal diameters of daughter roots in successive bearing root segments to the diameters of these segments for axile roots and higher-order LRs (Fig.…”

“…7). Most researchers have measured branching density in young plants (Varney et al, 1991;Lecompte et al, 2005;Ito et al, 2006) while our study considers the nodal roots of high whorls on mature plants. It has already been shown that diameter decrease is much steeper on nodal roots originating from the higher whorls .…”

“…It remains difficult to determine from the literature the extent to which these differences are due to species diversity, and that to which they are due to environmental diversity. Because of longitudinal variations in both root diameter and branching density (Lecompte et al, 2005), to further elucidate this important new aspect of root development, it is proposed to consider these relationships at the scale of the root segment, instead of at that of the whole root, as is more usual (Draye, 2002;Lecompte and Pagès, 2007;Bécel et al, 2012). Thus, our study relies on analysis of large numbers of roots and of several orders of branching in field-grown maize plants.…”

Water extraction and implications on soil moisture sensor placement in the root zone of banana

“…Yet, there are other studies indicating that the diameter of lateral roots was also a highly variable factor in the soil (Yorke and Sagar, 1970;Cahn et al, 1989;Varney et al, 1993;Jordan et al, 1993;Thaler and Pagès, 1996). In addition, Lecompte et al (2005) report that this variability was a consequence of factors like soil heterogeneity, root system structure, and availability and partitioning of carbon in the roots, but the relative contribution of each of these factors remain largely unknown. Other factors have been shown to influence water extraction by roots, such as differences in xylem maturation and in the number and diameter of xylem vessels, as well as differences in the formation of endodermis and exodermis with the development of sors positions.…”