Disposition des racines adventives autour de la tige de maïs (Zea mays L.)

Abstract

First, the root arrangement was studied on each internode considered separately. A x z test showed that roots were not arranged according to a random pattern (Table III). The assumption of a symmetrical arrangement has to be discarded too. On this assumption angles between roots would be equal to 360/1, I being the number of roots. This assumption could be accepted for I = 3 but could not be accepted for I = 2, or 1 = 4. For I = 3 the modal value of angles between roots was 120 degrees (Fig. 5). In this particular case lots of the root arrangements were close to a symmetrical arrangement (Fig. 4). For 1 = 2 very few values were equal to 180 degrees (Fig. 3). For I = 4 the modal classes of angles between roots were [70][71][72][73][74][75][76][77][78][79][80] degrees and [1 00-120J degrees (Fig. 6.a).The relative locations of roots belonging to 2 successive internodes (called E ; and E i+1 ) was also studied. It appeared that the roots of E i+1 occupied the more open angles between the roots of E ; . This result was shown by studying the locations of the roots of E i+1 relative by to the angles between roots of E ; classified by descending order. The following ratio : number of E i+1 roots between 2 roots of E ; /value of the angle between the 2 roots of E ; was constant for angles over 100 degrees but decreased for angles under 100 degrees (Fig. 7). When there was 1 E i+1 root between 2 E ; roots, this root was often close to the bisectrix of the angle (Fig. 8). When there were 2 E ;+ , roots between 2 E i roots, they tended to separate the whole angle into 3 parts equal (Fig. 9). These results showed that the positions of the roots on successive internodes tend to alternate. Possible origins of such arrangements are discussed.root morphology -phyllotaxis -stem -maize

Evaluation in field conditions of a three-dimensional architectural model of the maize root system: Comparison of simulated and observed horizontal root maps

“…The angle between roots was thus 27r/ni where ni is the number of roots on phytomer i. Radial angles of roots were shifted on successive phytomers in order to account for the alternating positions of roots (Pellerin et al, 1989). Insertion angles of roots (angle between the root and a vertical line) were randomly drawn from a normal distribution whose mean value and standard deviation were calculated from data published by Pellerin (1990, 1991).…”

A Gibbs point process on a finite series of circles:the insertion of the primary roots of maize around the stem

“…A preliminary study (Pellerin et al, 1989) shows that although the arrangement of the primary roots is not defined through a regular phyllotaxis as that of the leaves is, they are not independently uniformly distributed. In particular the angular disposition of a randomly chosen root on an internode depends on the other roots of this internode and on the roots of the preceding internode.…”

An Estimation Method of the Pair Potential Function for Gibbs Point Processes on Spheres

“…Five internodes were observed which are denoted by I2±I6, following Girardin et al's (1986) notations, I2 being the ®rst observed internode. A preliminary study (Pellerin et al, 1989) shows that the roots are not independently uniformly distributed, in particular the angular location of a randomly chosen root on an internode depends on the locations of the other roots on this internode and on the locations of the roots on the preceding internode. Since the roots appear simultaneously on an internode and successively on the next internodes, we can assume that the locations on the internode i given the preceding internodes will depend only on the locations on the internode i À 1.…”

“…The interactions between roots were analysed using the theory developed above. The primary roots have an important physical effect on the stem stability (Pellerin et al, 1990) and also on the hydric and mineral nutrition (Pellerin et al, 1989) because they determine the root system. A complete description of the structure of maize plant can be found in Girardin et al (1986).…”