Annals of Botany 90: 43-51, 2002
© 2002 Annals of Botany Company
Number, Position, Diameter and Initial Direction of Growth of Primary Roots in Musa
1 INRA, Unité de recherche sur les Plantes et Systèmes de culture Horticoles, Domaine Saint Paul, Site Agroparc, 84914 Avignon Cedex 9, France, 2 Institut National Agronomique Paris-Grignon, Département AGER, 16 rue Claude Bernard, 75005 Paris and 3 INRA Centre Antilles-Guyane, Unité Agropédoclimatique de la Zone Caraïbe, Domaine Duclos, 97170 Petit-Bourg, Guadeloupe, French West Indies
* For correspondence. Fax +33 (0)4 32 72 24 32, e-mail lecompte{at}avignon.inra.fr
Received: 24 September 2001; Returned for revision: 9 January 2002; Accepted: 17 March 2002
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
To understand soil colonization by a root system, information is needed on the architecture of the root system. In monocotyledons, soil exploration is mainly due to the growth of adventitious primary roots. Primary root emergence in banana was quantified in relation to shoot and corm development. Root emergence kinetics were closely related to the development of aerial organs. Root position at emergence on the corm followed an asymptotic function of corm dry weight, so that the age of each root at a given time could be deduced from its position. Root diameter at emergence was related to the position of the roots on the corm, with younger roots being thicker than older ones. However, root diameters were not constant along a given root, but instead decreased with the distance to the base; roots appear to be conical in their basal and apical parts. Root growth directions at emergence were variable, but a high proportion of the primary roots emerged with a low angle to the horizontal. Further research is needed to evaluate whether these initial trajectories are conserved during root development. Results presented in this study are in good agreement with those reported for other monocotyledons such as maize and rice. They give quantitative information that will facilitate the development of models of root system architecture in banana.
Key words: Adventitious roots, banana, Musa acuminata ‘Grande Naine’, root diameter, root emergence, root direction of growth.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Dry matter accumulation in banana plantations can be very high provided that the plants can obtain sufficient water and nutrients (Johns and Vimpany, 1999). The influence of root length densities (cm cm–3) on water and nutrient uptake has often been emphasized (Hamblin and Tennant, 1987; Smucker and Aiken, 1992). To optimize the supply of water and nutrients in space so that they are readily acquired by roots, information on the kinetics of root system development and the spatial arrangement of roots is needed. There are a few quantitative studies on Musa root development in the field which report total root lengths or masses per unit soil volume (Irizarry et al., 1981; Araya et al., 1998; Brisson et al., 1998). However, these data, derived from soil-based approaches (Van Noordwijk and Van de Geijn, 1996), are difficult to interpret since they give information on root development which integrates the various root growth potentials in a given environment, the influence of local growth conditions in the soil and overall plant regulation at the scale of the whole root system. Furthermore, such methods are not predictive. Alternative approaches, based on the study of root system architecture, can provide a more comprehensive understanding of the rooting process, while models of root architecture should assist our understanding of water and nutrient acquisition by the plant (Somma et al., 1998).
There are many reports on root system architecture in the literature, e.g. for maize (Pagès and Pellerin, 1994; Pellerin and Pagès, 1994), pea (Tezera Tsegaye et al., 1995), sunflower (Aguirrezabal and Tardieu, 1996) and oil-palm (Jourdan and Rey, 1997). As primary roots play a major role in the dynamics of soil exploration, the first step in a study of root architecture is the study of the emergence of these primary roots (Pagès et al., 2000). Literature on banana primary roots, although extensive, is essentially qualitative. It is known that these roots have several anatomical characteristics in common with other monocotyledons (Riopel and Steeves, 1964; Riopel, 1966). For maize (Picard et al., 1985), wheat (Pinthus, 1969; Klepper et al., 1984) and rice (Nemoto and Yamazaki, 1986), nodal (or crown) primary root emergence is closely related to leaf development. In banana, Skutch (1932) reported that groups of four adventitious primary roots arise from the corm, while Kwa (1993) showed that in several cultivars root poles are formed between the phytomer nodes, with one to five roots arising from each pole. However, nodes and internodes are not apparent on the corm surface. Depending on their time of emergence, primary roots of monocotyledons can have different morphological characteristics (Picard et al., 1985; Nemoto and Yamazaki, 1986; Varney et al., 1991). While many studies on banana are based on observations of root emergence at the corm surface (e.g. Beugnon and Champion, 1966; Mohan and Rao, 1984), no quantitative information is available on the relationship between time, corm development and root position on the corm at emergence. Beugnon and Champion (1966), working with the banana cultivar ‘Poyo’ (AAA genome, Cavendish subgroup), reported that root emergence was cyclical, but this was not confirmed by Gousseland and Lavigne (1984) for another AAA cultivar. Both studies showed that root emergence ceased at flowering. It is unclear whether primary roots have the same morphological characteristics. Swennen et al. (1986) tried to distinguish, under hydroponic conditions, between long, thin ‘feeder’ roots and short, thick ‘pioneer’ roots. However, this distinction has not been investigated in the field. Field and rhizotron studies (Lecompte et al., 2001) have shown that the banana tree root system is highly hierarchical between root orders, with mean growth rates ranging from 2·3 cm d–1 for primary roots to 0·32 cm d–1 for second order laterals. However, there was still great variability in primary root growth rates in the field; this could have arisen either from a difference in growth potential between roots, or from the effect of a non-uniform soil environment, or both. Several studies have shown that most Musa roots develop in the first 0–30 cm of soil (Sioussaram, 1968; Irizarry et al., 1981; Araya et al., 1998), but roots can also reach considerable depths (Summerville, 1939), with some roots growing almost vertically.
The objective of this work was to provide quantitative information on primary root emergence of banana trees in the field. The number, pattern of emergence, positions, diameters and growth directions of the roots were studied over the 3 months following planting.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Site and plant material
The experiment was carried out at CIRAD, Neufchâteau, in Guadeloupe, French West Indies (16°09'N, 61°16'W, altitude 485 m) during the 1999 rainy season (beginning on 1 June and ending on 6 September). The soil was an Andosol (Mollic Andosol, FAO classification, 1998), with a clay–loam texture (62 % clay, 32 % loam, 6 % sand), a high organic matter content (6·7 %), a cation-exchange capacity (CEC) of 9·21 meq 100 g–1 and a pH (water) of 6·28. The soil was loosened to a depth of 45 cm using a single, large ploughshare. Mean bulk density at –10 kPa at 15 cm depth was 0·837 Mg m–3. The banana trees used in the experiments originated from tissue culture of ‘Grande Naine’ (Musa acuminata, AAA genome, Cavendish subgroup) clones, hardened in a nursery for 3–4 weeks until eight to ten leaves had emerged. The banana trees were planted on a 2·35 m square grid, giving a density of 1800 plants ha–1. The plants were fertilized as follows: Dolomitic limestone (250 kg ha–1) and ammonium sulfate (180 kg ha–1) were applied 6 and 13 d after planting, respectively, and an N : P : K : Mg (15 : 4 : 30 : 8, 180 kg ha–1) fertilizer was applied every 15 d, from day 5 to the end of the experiment. Weeds were controlled chemically. Plants were rainfed. Soil moisture was controlled using tensiometers placed at depths of 5, 15, 40 and 60 cm, with four replications at each depth. Soil water potentials and rainfall during the experiment are shown in Fig. 1. Rainfall was heavy and mean soil water potential remained high throughout the experiment. On days 19 and 30 after planting, soil water potential at a depth of 5 cm reached about –30 and –35 kPa, respectively.
|
Daily mean air temperature was almost constant throughout the experiment, ranging from 24·2 to 26·3 °C, so plant growth analysis could either be made on a chronological or a degree-day basis, 1 d being equivalent to 11·45 degree-days (with a base temperature of 14 °C).
Root measurements
Six series of excavations were made at 2-week intervals; five plants were sampled for the first four series and three plants for the last two series. For each plant, either all (for the three first series) or half (for the last three series) the primary roots were carefully separated from the surrounding soil and collected for further measurements. Roots were marked and cut between 5 and 10 cm away from their insertion on the corm, and placed in a 1 : 5 mixture of ethanol and tap water. Measurements were made on the day of excavation. A total of 339 primary roots was collected. The total length, basal diameter (Db), diameter at 5 cm away from the base (D5b), and diameter at 5 (D5a) and 15 cm (D15a) away from the apex were measured for each root (Fig. 2). Root apex positions were determined from their distance to the pseudo-stem on the horizontal plane (x coordinate) and their depth (z coordinate, corrected for root depth at emergence). For each root, the angle 
between the horizontal plane and the line passing through the point of root insertion and the apex position was calculated: = tan–1 (z/x). For young roots which were roughly straight, this angle was the same as for the initial direction of growth. The trajectory was only recorded for newly emerged roots.
|
Plant measurements
Each plant was separated into leaves, pseudo-stem and corm, and the fresh and dry (after drying for 72 h at 65 °C) weights of these organs measured. Prior to the mass measurements, the total number of roots on each corm was counted and the position of each root insertion was recorded as the curvilinear distance along the surface of the corm from the base of the corm to the point of root insertion. This distance was called ‘distance to the base of the corm’ (DBC). For some analyses, roots were grouped depending on their DBC into classes with 1 cm increments, i.e. roots whose DBCs were between 0 and 1 cm, 1 and 2 cm, and so on.
Data analysis
All linear and non-linear regressions, parameter adjustments and analyses of variance were made using various procedures of the SAS software (SAS system, 1988).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Pattern of root emergence
Plots of corm dry weight and total shoot dry weight (leaves + pseudo stem + corm) against cumulative degree-days were very similar in shape (Fig. 3) and both curves could be fitted to an exponential function. Corm dry weight (Cdw, g) could be modelled as follows:
|
Cdw = a eb Cdd(1)
where Cdd is the sum of degree-days, a is the corm dry weight at planting, and b is a fitted rate parameter. Pseudo-stem and leaf dry weights followed the same trend (data not shown). Mean corm dry weight represented 12·4 % of the total shoot dry weight [coefficient of variation (CV) = 21 %]. The total number of primary adventitious roots per plant was closely correlated with corm dry weight (Fig. 4). At around 1000 degree-days, corm dry weight was 100 g and about 120 primary roots had emerged. The number of roots is related to corm dry weight by the following equation:
|
N = a + b (Cdw)c(2)
where N is the number of emerged primary roots, Cdw is corm dry weight, and a, b and c are parameters. On a daily scale, root emergence can therefore be considered continuous throughout the experiment, and the number of primary roots emerging per degree-day can be calculated from eqns (1) and (2). Results are shown in Fig. 4. The pattern of primary root emergence increased exponentially, from 0·025 roots per degree-day at planting to 0·25 roots per degree-day at 1000 degree-days.
Position of roots on the corm
Figure 6 shows the number of roots as a function of cumulative degree-days, classified by distances to the base of the corm (see Materials and Methods). Eight classes were chosen arbitrarily, from 0–1 cm to 7–8 cm to the base. The number of roots per class was counted for each plant. In the first class (0 < DBC < 1 cm), the number of roots was quite stable whatever the age of the corm, decreasing slightly for older corms, indicating that root emergence in this class had ceased before the first sampling date. For all other classes, the number of primary roots started to increase after a given degree-day sum, this sum being higher for higher order classes. At the end of the experiment, the number of roots in the 6–7 cm and 7–8 cm classes was apparently still increasing. In the 1–2 cm to 4–5 cm classes the number of roots ceased to increase after a variable period of time. There was considerable variability in the number of roots within a class at a given date, probably due to variability in the plant sample. However, the distinction between geometric classes might not have reflected the exact separation between the different internodes. Such morphological traits, unfortunately not apparent at the corm surface, would have been more suitable for inter-plant comparisons. The final number of roots also varied between classes. This number was higher for the upper classes. It appeared from the data of Fig. 5 that initiation was not strictly acropetal, since roots could emerge in one class before the end of root emergence in the lower class. Therefore, the upper and lower limits of root emergence on the corm at a given date were determined. For each plant excavated, the highest DBC in the total pool of root insertions was measured, and was called DBCmax. An asymptotic regression model (specifically a monomolecular function) was fitted to estimate DBCmax from corm dry weight. The minimum DBC, DBCmin, below which there is no longer root emergence at the surface of the corm at a given thermal time was calculated as follows: for each class, the mean number of roots for three consecutive excavations was compared with the mean number of roots for the last three excavations (the sixth series). At this time, it was assumed that root emergence had ceased for the six lower classes (Fig. 6). It was assumed that root emergence in a given class had stopped when the first mean was higher than the last one, i.e. when the mean number of roots at a given time was greater than the mean number of roots at a time when emergence had stopped. Thus, a series of values was obtained, and DBCmin was calculated by interpolation between these points. Results are given in Table 1, and DBCmax and DBCmin are plotted in Fig. 7. Table 1 shows that there is a superposition in class filling, as root emergence in a given class ceases long after the beginning of emergence in the next class. However, these results give an estimate of the position of root emergence during corm development, indicating that root emergence at a given time occurs only in a narrow band on the upper side of the corm. This estimate of root position was tested for young roots, whose lengths did not exceed 20 cm. Assuming a mean root growth rate of 2·3 cm d–1 (Lecompte et al., 2001), none of these roots was older than 9 d. The DBC for these roots was plotted against corm dry weight, along with DBCmin and DBCmax (Fig. 7). Almost all the young roots were located between DBCmin and DBCmax.
|
|
|
|
Root diameter
Irrespective of root position, primary root basal diameters varied from 1·8 to 9·5 mm. There was a highly significant effect of the DBC on the diameter of primary roots (P < 0·001). Figure 8 plots the mean root basal diameters for young roots, whose length did not exceed 20 cm, for different positions on the corm. There was a significant increase in root basal diameter with DBC. Thus, the diameter of newly emerging roots increased with plant growth. However, for a given DBC class, there was much variability in root diameter when the whole pool of roots, irrespective of length or age, was considered (data not shown). Mean root basal diameters in a given DBC class were thus observed from roots excavated at different sampling dates (Fig. 9). For all classes there was an increase in root basal diameter with time. Mean root diameter in a given class could increase during the time of root emergence (indicated by arrows in Fig. 9), as the diameter of emerging roots was increasing. However, mean root diameter in all but the last class also increased after the end of the emergence process. This means that the basal diameter of emerged roots tended to increase with time.
|
|
Changes in diameter along the roots were evaluated from calculations of different ratios between successive positions. Overall mean values of Db/D5b and D15a/D5a were 1·21 ± 0·2 and 1·13 ± 0·19, respectively, indicating that proximal and distal root zones were slightly conical. The mean value of D5b/D15a was 1·14 ± 0·24. As the distance between the two points of measurement was variable, the ratio was calculated for different root lengths (Table 2). A significant difference was observed between the ratio for the group of roots shorter than 25 cm (roots for which D5b and D15a were measured at approximately the same position) and the ratio in the other groups. No significant trend appeared for a continuous decrease in root diameter along the central zone of the root although, as indicated by the mean value of the ratio, the diameter towards the apex was generally lower than the diameter towards the base. Therefore, conical regions seem to be restricted to the basal and distal root extremities. Detailed measurements along the whole root profiles would have been necessary to verify this hypothesis.
|
Direction of growth
Figure 10A shows the distribution of growth angles to the horizontal for young roots. Roots grew in all directions, but the number of roots decreased as the angle to the horizontal increased. One-third of the roots had an initial angle to the horizontal plane of less than 15°, and more than 70 % had an angle less than 45°. We noted no influence of root position on these initial trajectories: as shown in Fig. 10B, the frequency of angles did not vary with DBC class, and the differences among classes were not significant (P = 0·41). There was also no effect of root diameter on the initial direction of a root’s growth.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Number of roots
Root emergence in banana is a very organized process as dynamics of emergence, positions, directions of growth and growth potentials derived from the root diameters can be determined from a few equations, mainly dependent on corm development. In several monocotyledons such as maize (Picard et al., 1985) and wheat (Klepper et al., 1984), the cumulative number of adventitious primary roots has been related to the number of leaves. We have shown here that there is a quantitative relationship between corm growth and root emergence (Fig. 4). A relationship between the total shoot weight and the number of roots has also been found by Pellerin (1991) for maize. Such relationships are interesting because they link growth phenomena to developmental phenomena (see Bonhomme, 2000), and can therefore be used for modelling over a wide range of environmental conditions, where stresses only affect growth dynamics without changing developmental patterns. For example, Pellerin (1991) showed that shading affected the relationship between the sum of degree-days and total shoot biomass, but that the relationship between total shoot biomass and the number of roots was the same at any level of shading. Here we propose a simple model predicting root emergence on a thermal time basis (Fig. 5).
Root position
As node junctions were not apparent at the corm surface of the plants studied, root position on the corm was studied in terms of the distance to the base of the corm. Using first cycle banana plants (i.e. plants originating directly from tissue culture), we found no evidence that roots emerged in groups of three or four, as reported by Skutch (1932) on suckers, but precise anatomical observations would probably have been necessary to distinguish root poles. However, in a qualitative analysis, Kwa (1993) showed that both the number of poles per internode and the number of roots per pole were variable. Nevertheless, our study confirmed previous observations on root emergence. Roots emerge from the upper part of the corm so that it was possible to fit a function relating the mean position of the roots at emergence to corm development (Fig. 7). Similar relationships were found for maize (Picard et al., 1985), where root emergence on an given phytomer occurred during a definite period in plant growth. It was thus possible to predict for maize the appearance of new roots on a phytomer as a function of degree-day sums (Pellerin and Pagès, 1994). Such a method could also be applied to the banana root system. However, primary root emergence in banana did not appear to be strictly acropetal. Therefore, only ranges of corm dry weights and plant age at root emergence could be inferred from the measurement of root positions.
Root diameter
Root basal diameter depends on root position on the corm (Fig. 8), hence also on the time of root emergence. This has also been reported for maize (Picard et al., 1985) and rice (Nemoto and Yamazaki, 1986). In the latter study, the authors found a correlation between the diameter of the primary roots and that of the root-forming zone from which they emerged. There are no studies on the time of formation and the growth of root poles in Musa, but it can be assumed that the mechanisms are similar. These differences in root diameter could have an influence on root architecture via the number of lateral roots arising from each primary root because in Musa the number of lateral root ranks is correlated with root diameter (Charlton, 1982; Draye et al., 1999). Further research is needed to clarify this point. We have also shown that the root basal diameter increased during root development and that the root diameter decreased along the root from the base to the apex (Fig. 9; Table 2). This decrease was irregular, with central portions of the roots showing little evolution while basal and apical parts were more conical. Radial expansion due to tissue maturation could have occurred in the apical zones. This would agree with Riopel and Steeves (1964), who reported that tissue maturation of primary roots in Musa is complete more than 1 m away from the apex. However, the decrease in diameter along the root might also have arisen from a decrease over time of root apical diameter. We noted no apparent relationships between the length of the roots and their apical diameter, but dynamic observations would be necessary to test this hypothesis. There is evidence in the literature that a root’s diameter is not constant along its length in monocotyledons. For example, in maize, Picard et al. (1985) showed that root diameter some centimetres away from the base is less than that at the base itself. As root diameter is a direct consequence of carbon allocation to the various parts of the root, it is important to clarify the origin of diameter changes along the root profile. The fact that root diameters are not constant between roots or along a root should be taken into account for a more accurate model of root system architecture.
Growth directions
The initial growth direction of roots was largely horizontal, with one-third of the roots having an initial angle to the horizontal of less than 15°. However, roots emerged growing in all directions, with a few growing almost vertically downwards. The mean angle to the horizontal was 30°. These results agree with those of Summerville (1939) for Cavendish cultivars, who stated that the general tendency of the roots was to penetrate the soil at an angle between 20° and 30° to the horizontal. It is unlikely that these initial directions were influenced by the surrounding soil as there were few, if any, physical constraints. The position of a root on the corm had no effect on this distribution. Tardieu and Pellerin (1990) also noted that the initial penetration angle of maize roots into the soil did not vary among phytomers. However, they showed that this initial angle did not account for differences between root growth directions because there was a positive curvature in the growth line of many roots some centimetres away from the stem. Further research is needed to discover whether such modification of root growth line exists in the banana tree root system. Yamazaki et al. (1981) found a significant correlation between growth direction and root diameter for rice roots, with the thicker roots tending to grow more vertically. In this study, root diameter was correlated with position on the corm; however, we found no correlation between root position and root growth direction, and there was also no direct correlation between root diameter and initial root growth direction.
This work has shown that primary root emergence in Musa is very similar to nodal root emergence in other major monocotyledons. It is a first step in an architectural analysis of the banana tree root system. The relationships proposed in this study are functional and could be readily used in a model of root system architecture. Varietal diversity could also be explored on the basis of these relationships.
|
ACKNOWLEDGEMENTS |
|---|
We thank Thierry Bajazet and Simon Leinster for their help in data collection. This work received financial support from the French Centre de Coopération Internationale en Recherche Agronomique pour le Développement, CIRAD-FLHOR.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
-
Aguirrezabal LAN, Tardieu F. 1996. An architectural analysis of the elongation of field grown sunflower root systems. Elements for modelling the effects of temperature and intercepted radiations. Journal of Experimental Botany 47: 411–420.[ISI]
Araya M, Vargas A, Cheves A. 1998. Changes in distribution of roots of banana (Musa AAA, cv talerg) with plant height, distance from the pseudostem and soil depth. Journal of Horticultural Science and Biotechnology 73: 437–440.
Beugnon M, Champion J. 1966. Etude sur les racines du bananier. Fruits 21: 309–327.
Bonhomme R. 2000. Bases and limits to using ‘degree.day’ units. European Journal of Agronomy 13: 1–10.
Brisson N, Dorel M, Ozier-Lafontaine H. 1998. Effects of soil management and water regime on the banana growth between planting and flowering. Simulation using the STICS model. Acta Horticulturae 490: 229–238.
Charlton WA. 1982. Distribution of lateral root primordia in root tips of Musa acuminata colla. Annals of Botany 49: 509–520.
Draye X, Delvaux B, Swennen R. 1999. Distribution of lateral root primordia in root tips of Musa. Annals of Botany 84: 393–400.
Gousseland J, Lavigne C. 1984. Enracinement et émission racinaire du bananier (Giant Cavendish cv 901) dans les andosols de la Guadeloupe. Fruits 39: 107–111.
Hamblin AP, Tennant D. 1987. Root length density and water uptake in cereals and grain legumes: how well are they correlated? Australian Journal of Agricultural Research 38: 513–527.[CrossRef][ISI]
Irizarry H, Vicente-Chandler J, Silva S. 1981. Root distribution of plantains growing on five soil types. Journal of Agriculture of University of Puerto Rico 65: 29–34.
Johns GG, Vimpany IA. 1999. Effect of high rates of potassium chloride fertiliser on banana leaf conductance, plant growth, nutrient concentration and root death under contrasting watering regimes. Australian Journal of Experimental Agriculture 39: 211–219.[CrossRef]
Jourdan C, Rey H. 1997. Architecture and development of the oil-palm (Elaeis guineensis Jacq.) root system. Plant and Soil 189: 33–48.[CrossRef]
Klepper B, Belford RK, Rickman RW. 1984. Root and shoot development in winter wheat. Agronomy Journal 76: 117–122.
Kwa M. 1993. Architecture, morphogénèse et anatomie de quelques cultivars de bananiers. PhD Thesis, Université de Montpellier II, France.
Lecompte F, Ozier-Lafontaine H, Pagès L. 2001. The relationships between static and dynamic variables in the description of root growth. Consequences for field interpretation of rooting variability. Plant and Soil 236: 19–31.[CrossRef]
Mohan N, Rao VNM. 1984. The effect of plant density on the banana root system. South Indian Horticulture 32: 254–257.
Nemoto K, Yamazaki K. 1986. The successive stem growth and its relation to the diameters and the number of primary roots on main axes of rice plants. Japanese Journal of Crop Science 51: 352–359.
Pagès L, Pellerin S. 1994. Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.). II. Density, length and branching of first order lateral roots. Plant and Soil 164: 169–176.[CrossRef]
Pagès L, Asseng S, Pellerin S, Diggle A. 2000. Modelling root system growth and architecture. In: Smit AL, ed. Root methods. Berlin: Springer-Verlag.
Pellerin S. 1991. Effet d’une réduction du rayonnement incident sur l’émission des racines adventives du maïs en début de cycle. Agronomie 11: 9–16.
Pellerin S, Pagès L. 1994. Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.). I. Elongation of seminal and nodal roots and extension of their branched zone. Plant and Soil 164: 155–167.[CrossRef]
Picard D, Jordan MO, Trendel R. 1985. Rythme d’apparition des racines primaires de maïs (Zea mays L.). I. Etude détaillée pour une variété en un lieu donné. Agronomie 5: 667–676.
Pinthus MJ. 1969. Tillering and coronal root formation in some common and durum wheat varieties. Crop Science 9: 267–272.
Riopel JL. 1966. The distribution of lateral roots in Musa acuminata ‘gros michel’. American Journal of Botany 53: 403–407.[CrossRef]
Riopel JL, Steeves TA. 1964. Studies on the root of Musa acuminata cv Gros Michel. I. The anatomy and development of main roots. Annals of Botany 28: 475–495.
SASInstitute Inc. 1988. SAS/STAT guide for personal computers. Cary, NC.
Sioussaram D. 1968. Observations préliminaires sur l’enracinement des bananiers dans les sols de la station de Neufchâteau, Guadeloupe. Fruits 23: 473–479.
Skutch AF. 1932. Anatomy of the axis of banana. Botanical Gazette 43: 233–258.[CrossRef]
Smucker AJM, Aiken RM. 1992. Dynamic root responses to water deficits. Soil Science 154: 281–289.
Somma F, Hopmans JW, Clausnitzer V. 1998. Transient three-dimensional modeling of soil water and solute transport with simultaneous root growth, root water and nutrient uptake. Plant and Soil 202: 281–293.[CrossRef][ISI]
Summerville WAT. 1939. Root distribution of the banana. Queensland Agricultural Journal 52: 376–392.
Swennen R, De Langhe E, Janssen J, Decoene D. 1986. Study on the root development of some Musa cultivars in hydroponics. Fruits 41: 515–524.
Tardieu F, Pellerin S. 1990. Trajectory of the nodal roots of maize in fields with low mechanical constraints. Plant and Soil 124: 39–45.[CrossRef]
TezeraTsegaye T, Mullins CE, Diggle AJ. 1995. An experimental procedure for obtaining input parameters for the ‘rootmap’ root simulation program for peas (Pisum sativum L.). Plant and Soil 172: 1–16.[CrossRef]
VanNoordwijk M, Van de Geijn SC. 1996. Root, shoot and soil parameters for process-oriented models of crop growth limited by water or nutrients. Plant and Soil 183: 1–25.[CrossRef]
Varney GT, Canny MJ, Wang XL, McCully, ME. 1991. The branch roots of Zea. I. First order branches, their number, sizes, and division into classes. Annals of Botany 67: 357–364.
Yamazaki K, Morita S, Kawata S. 1981. Correlations between the growth angles of crown roots and their diameters in rice plants. Japanese Journal of Crop Science 50: 452–456.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||