Maize nodal root ramification: Absence of dormant primordia, root classification using histological parameters and consequences on sap conduction

Abstract

A b s t r a c tMaize plants grown in field conditions were used to describe the histological organisation of the nodal roots, those of their laterals, and also to test the presence of critical stages where the subsequent capability for growth and development of young laterals was determined irreversibly. The absence of undeveloped primordia, which stop their development before boring through the nodal mother-root epidermis, proved that the number of laterals could not be regulated between the differentiation and the emission stage. Cross sections performed on nodal roots beared by the internodes 2, 4 and 6 and their long (>3 cm) and short (<3 cm) laterals showed that: -The short laterals have almost the same root and stele diameter, cortex width and xylem size regardless of the insertion position of their mother root. Consequently they stopped their development at nearly the same stage, which seems to be concomitant with late metaxylem vessel differentiation. Thus, 92% of these short roots had only one of these vessels. On the contrary, the dimensions of the tested histological parameters, as well as the numbers of late and early metaxylem vessels and of xylem poles increased with internode rank for both long laterals and nodal roots. Moreover, for the nodal roots issued from internode 6, important decreases (up to 50%) in the sizes of most of the measured parameters were observed along the roots with the distance from the stem insertion point. Complementary experiments performed in mist boxes, under strict homogeneous conditions, showed that the observed variability is not generated by the culture medium. -Up to 750/xm, the root diameter is correlated to most of the histological characters tested. -Nodal roots have a higher proportion of xylem than lateral roots. Consequently their conduction abilities, evaluated using the C/E ratio of Hagen-Poiseuille's law, were particularly important. -No relationship was found between the diameter of a nodal root and those of its laterals.

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

“…However, Green and Clothier (1995) studied water extraction of kiwifruit vines and observed that root water uptake was more dependent on soil water availability than of thin roots distribution. 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.…”

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

“…These tend to optimize the ratio of root length (and hence root surface area for uptake) to root weight (investment). However, decreased root diameter limits root penetration through the soil (Materechera et al, 1992;Clark et al, 2008), and roots must also develop internal structures dedicated to water and nutrient transport (Jordan et al, 1993;Jaramillo et al, 2013). From a developmental point of view, apical diameter reflects the size of the apical meristem.…”

Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.)

“…On maize partic-ularly, the water and mineral transfer resistances are better identified (McCully and Canny, 1988;Peterson et al, 1993) and the importance of the root connections have been demonstrated recently (McCully and Mallet, 1993). The variations in the morphogenetic capacities between maize roots have been studied according to various criteria: live duration (Fusseder, 1987), apical diameter and growth rate (Cahn et al, 1989;Feldmann, 1979), length (Iijima et al, 1991), and anatomy (Jordan et al, 1993;. All these works pointed out the interest of an architectural approach.…”