Modifications expérimentales de la morphogenèse du système racinaire de jeunes semis d'hévéa (Hevea brasiliensis)

2000 ◽  
Vol 78 (11) ◽  
pp. 1460-1468
Author(s):  
Yannick Le Roux ◽  
Loïc Pagès
Keyword(s):  
Root System ◽  
Hevea Brasiliensis ◽  
High Plasticity ◽  
External Diameter ◽  
Active Growth ◽  
Experimental Block ◽  
Tap Root ◽  
Large Growth ◽  
Growth Correlations ◽  
Secondary Roots

Determining factors involved in root polymorphism were studied in young hevea seedlings (Hevea brasiliensis Mull. Arg.) following an experimental block of the tap root in the laboratory, using minirhizotron grown plants. The authors show that this block promotes different morphogenetic modifications in the root system: regrowth of the early secondary roots having the largest external apex, high density of the ramification zone in the taproot apical area, large growth (associated with an important external diameter at the apex), and orthogeotropism of the sequential secondary roots emerging after the treatment in the zone close to the blockage site. The evolution of morphogenetic potentialities of sequential secondary roots following an inhibition of the taproot growth was confirmed using other cultivation set ups, under controlled (aeropinic) or natural (underground observation windows) conditions. Overall results show that the expression of the early morphogenetic potential acquired by the roots can be modulated by the environmental conditions exerting their effect during their development. Notably, the active growth correlations existing between the taproot and the secondary axes confer a high plasticity to the root system which will permit its adaptation to heterogeneous or restricting environments. These correlative influences are discussed in the frame of an hormono-trophic model for the root morphogenetic determinism, essentially based on taproot dominancy.Key words: articial block, growth correlations, root system, morphogenesis, minirhizotron, Hevea brasiliensis.[Journal translation]

Réaction géotropique des différents types de racines chez l'hévéa (Hevea brasiliensis)

1996 ◽  
Vol 74 (12) ◽  
pp. 1910-1918 ◽  
Author(s):  
Yannick Le Roux ◽  
Loïc Pagès
Keyword(s):  
Root System ◽  
Hevea Brasiliensis ◽  
Vertical Plane ◽  
Growth Direction ◽  
Vertical Position ◽  
Different Types ◽  
Original Direction ◽  
Growth Development ◽  
Secondary Roots ◽  
Root Observation

To describe the different types of geotropic reactions of hevea (Hevea brasiliensis), young seedlings were cultivated in root observation boxes and submitted to a double gravistimulation (90° rotation of the minirhizotrons in the vertical plane). It was demonstrated that the taproot is a strongly orthogeotropie organ since it resumed rapidly its prestimulation vertical position. Morphological and morphogenetic modifications were associated with the geotropic response: reduced speed of growth coupled with a reduction of the apical diameter as well as an alteration of ramification density in the curving zone and the following one. Early secondary roots showed a somewhat reduced orthogeotropism that was weaker as the growth direction before gravistimulation was more distant from the vertical. Secondary roots of the acropetal sequence were semiplagiotropic, that is only those roots oriented upward after the gravistimulation resumed, more or less, the original direction. Tertiary roots didn't respond to the gravistimulation and therefore were ageotropic. Complementary observations conducted in large laboratory rhizotrons showed that late forming secondary roots were plagiotropic in their younger stages, thereafter loosing most of their sensitivity to gravity. Quaternary roots were ageotropic. On the basis of these data, a geotropic gradient was defined within the hevea root system, where the strongly responding taproot and late secondary roots are opposed to the weakly or nonresponding tertiary and quaternary roots. Functional significations of these differential geotropic reactions in different hevea root types are discussed. Keywords: geotropism, gravistimulation, root system, growth, development, morphogenesis, root observation box, Hevea brasiliensis. [Journal translation]

Développement et polymorphisme racinaires chez de jeunes semis d'hévéa (Hevea brasiliensis)

1994 ◽  
Vol 72 (7) ◽  
pp. 924-932 ◽  
Author(s):  
Yannick Le Roux ◽  
Loïc Pagès
Keyword(s):  
Root System ◽  
Hevea Brasiliensis ◽  
System Development ◽  
Lateral Roots ◽  
Rubber Tree ◽  
Morphological Plasticity ◽  
Daily Basis ◽  
External Diameter ◽  
First Order ◽  
Root Observation

The major problems (bad anchorage, water stress, and root disease) with the cropping of the rubber tree (Hevea brasiliensis) are related to the architecture of its root system. So, the morphogenetic properties of the various roots that emerge during the development of the young seedlings are described to improve our understanding of the dynamics of root system architecture. In this study, the development of the root system of 12 seedlings grown for 40 days in root observation boxes has been recorded on a daily basis and analysed. Additional observations were also made on plants grown in pots or in the field for a 60-day period. This analysis of the sequential differentiation of the root system allowed us to distinguish five different root types according to their spatial and temporal location at emergence: (i) taproot, (ii) early first-order lateral roots, (iii) acropetal first-order lateral roots, (iv) late first-order lateral roots, (v) second-order lateral roots. Large variations and close relationship were found within the growth and branching characteristics on one hand, and within anatomical characteristics on the other (number of xylem poles, external diameter, and stele diameter). These between-type variations were also observed, to a lesser extent, among roots from the same type. The continuity of these development characteristics, which were shown to be acquired early, led us to characterize a morphogenetic gradient. This gradient is a reference scale to understand the morphological plasticity of the root system growing in other mediums. Key words: root system, development, morphogenesis, anatomy, root observation box, Hevea brasiliensis.

scholarly journals Rooting in the Desert: A Developmental Overview on Desert Plants

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 709
Author(s):  
Gwendolyn K. Kirschner ◽  
Ting Ting Xiao ◽  
Ikram Blilou
Keyword(s):  
Root System ◽  
Developmental Plasticity ◽  
Root System Architecture ◽  
Desert Plants ◽  
Root Cortex ◽  
Date Palms ◽  
Beneficial Impact ◽  
Scarce Water ◽  
Sessile Organisms ◽  
Secondary Roots

Plants, as sessile organisms, have evolved a remarkable developmental plasticity to cope with their changing environment. When growing in hostile desert conditions, plants have to grow and thrive in heat and drought. This review discusses how desert plants have adapted their root system architecture (RSA) to cope with scarce water availability and poor nutrient availability in the desert soil. First, we describe how some species can survive by developing deep tap roots to access the groundwater while others produce shallow roots to exploit the short rain seasons and unpredictable rainfalls. Then, we discuss how desert plants have evolved unique developmental programs like having determinate meristems in the case of cacti while forming a branched and compact root system that allows efficient water uptake during wet periods. The remote germination mechanism in date palms is another example of developmental adaptation to survive in the dry and hot desert surface. Date palms have also designed non-gravitropic secondary roots, termed pneumatophores, to maximize water and nutrient uptake. Next, we highlight the distinct anatomical features developed by desert species in response to drought like narrow vessels, high tissue suberization, and air spaces within the root cortex tissue. Finally, we discuss the beneficial impact of the microbiome in promoting root growth in desert conditions and how these characteristics can be exploited to engineer resilient crops with a greater ability to deal with salinity induced by irrigation and with the increasing drought caused by global warming.

scholarly journals Landslides and the Urban Forest

2011 ◽  
Vol 37 (5) ◽  
pp. 213-218
Author(s):  
Robert Loeb ◽  
Samuel King
Keyword(s):  
Root System ◽  
Lateral Root ◽  
Urban Forest ◽  
Basal Area ◽  
Natural Area ◽  
Species Classification ◽  
Slope Steepness ◽  
Tap Root ◽  
Area Survey ◽  
Root Plate

Trees and saplings were felled and killed by rockslides and soil slides formed during the record breaking rains of May 1–2, 2010, in Radnor Lake State Natural Area, Nashville, Tennessee, U.S. The losses were analyzed by species; stem basal area; root plate diameter and depth; percent slope; occurrence in a rockslide or soil slide as well as species classification as a lateral root system species versus tap or heart root system species. The number of stems lost for each species had a distribution similar to the results of the 2009 Natural Area survey but the number of saplings was significantly underrepresented at the landslide sites. Tree deaths were nearly five times greater than saplings lost. Although there were nearly equal numbers of tree and sapling stems classified as possessing a lateral root system versus tap or heart root system, 74% of the sapling losses were from surface root system species. The means for root plate diameter and depth were significantly larger in rockslides than soil slides even though the mean stem basal area did not differ significantly. For both slide types, slope steepness was not correlated with root plate depth, root plate diameter, or stem basal area. Similarly for both root system classi-fications, slope steepness was not significantly correlated except for surface root system trees with root plate depth. Planting tap root system trees reduces the risk of landslide, but advances in the cultivation of taxa, such as hickory (Carya spp.), are needed to assure tap root preservation during transplantation.

Root Morphology and Secretion of two subtropical tree species to NH4+-N and NO3–-N Deposition

2020 ◽  
Author(s):  
Rui Zhang ◽  
Yi Wang ◽  
Zhichun Zhou
Keyword(s):  
Root Growth ◽  
Root System ◽  
Root Morphology ◽  
Tree Species ◽  
Southern China ◽  
N Deposition ◽  
Fibrous Root ◽  
Nitrogen And Phosphorus ◽  
Root Absorption ◽  
Tap Root

Abstract Background: Both NH4+ and NO3– are capable of greatly influencing plants’ growth and biomass. However, the belowground responses of subtropical trees to either NH4+ or NO3– deposition remain poorly understood. Here, we discuss how these two forms of N deposition can affect root development, and experimentally analyzed how they could impact nitrogen and phosphorus absorption in two types (broadleaved with a fibrous root system vs. conifer with a tap root system) of subtropical tree species. Results: In a greenhouse in southern China, 1-year-old S. superba and P. massoniana seedlings grown on P-limited and P-normal soil were treated with NaNO3 and NH4Cl solutions of 0, 80, and 200 kg N ha–1 year–1, corresponding to the control, N80, and N200 groups, respectively. Root phenotype characteristics and metabolism ability were measured after 8 months of growth. The results showed that the root morphology and physiology variables differed significantly between the two species under different N and P treatments. Although S. superba had a larger quantity of roots than P. massoniana, both its root growth rate and root absorption were respectively lower and weaker. N addition differentially affected root growth and activity as follows: (1) NO3–-N80 and NH4+-N80 increased root growth and activity of the two species, but NH4+-N80 led to thicker roots in S. superba; (2) NO3–-N200 and NH4+-N200 had inhibitory effects on the roots of P. massoniana, for which NH4+-N200 led to thinner and longer roots and even the death of some roots; and (3) NH4+-N could promote metabolic activity in thicker roots (> 1.5 mm) and the NO3–-N was found to stimulate activity in thinner roots (0.5–1.5 mm) in the fibrous root system having a larger quantity of roots, namely S. superba. By contrast, NO3–-N and NH4+-N had an opposite influence upon functioning in the tap root system with a slender root, namely P. massoniana. Conclusion: We conclude P. massoniana has a much higher root absorption efficiency; however, nitrogen deposition is more beneficial to the root growth of S. superba.

The root morphology of Lupinus angustifolius in relation to other Lupinus species

1993 ◽  
Vol 44 (6) ◽  
pp. 1367 ◽  
Author(s):  
JC Clements ◽  
PF White ◽  
BJ Buirchell
Keyword(s):  
Root System ◽  
Lateral Roots ◽  
Poor Performance ◽  
Alkaline Soils ◽  
Poor Growth ◽  
Wide Range ◽  
Proteoid Root ◽  
Primary Lateral ◽  
Secondary Roots ◽  
Coarse Soil

Commercial L. angustifolius cultivation is restricted to acid to neutral coarse-textured soils in Australia. An unsuitable root system may be part of the reason for the poor performance on fine-textured or alkaline soils. As a first step to examine this question plants of 12 annual Lupinus species were grown in a coarse soil with the aim of describing the range of root morphologies within the genus and to compare these to commercial L. angustifolius. A wide range of rooting patterns were observed. The differences in the dominance of the taproot was pronounced between species. The commercial genotype of L. angustifolius occupied an extreme within the range of root morphologies of the species. Roots of L. angustifolius consisted of a dominant taproot and a relatively high number of primary lateral roots but few secondary roots. In contrast, the primary, secondary and tertiary lateral roots of L. pilosus, L. mutabilis, L. atlanticus, L. palaestinus and L. micranthus were more dominant than the taproot. The length and distribution of primary lateral roots along the taproot also varied between species. The number of primary lateral roots fell rapidly with depth in L. angustifolius and L. mutabilis, while the other species had a more even distribution. L. angustifolius had a less extensive root system and relatively thick roots when compared to species such as L. albus and L. mutabilis. L. luteus also had relatively thick roots. The relatively thick roots and less extensive lateral root system in commercial L. angustifolius may partially explain its poor growth on fine-textured soils, where a greater proliferation of finer, lateral roots may be necessary. Proteoid root formation was observed for L. albus, L. cosentinii, L. pilosus, L. palaestinus, L. micranthus, L. digitatus, L. princei and L. atlanticus. They were particularly numerous in L. micranthus and L. albus. The structure of proteoid root clusters varied between species.

Relation between plant size and severity of root rot in subterranean clover

1983 ◽  
Vol 23 (121) ◽  
pp. 126
Author(s):  
MJ Barbetti
Keyword(s):  
Root System ◽  
Western Australia ◽  
Root Rot ◽  
Lateral Root ◽  
Inverse Relationship ◽  
Subterranean Clover ◽  
Plant Size ◽  
Tap Root ◽  
The Relationship

Investigations were carried out in south-western Western Australia in 1977-78 to assess the relationship between dry weights of subterranean clover tops and roots and the severity of root rot. An inverse relationship was established between the severity of rotting of the tap root system and the plant top and the root dry weights. There was no relationship between the severity of root rot of the lateral root system and the plant top and root dry weights.

The Growth and Development of Caltha introloba F. Muell. II. The Regulation of Germination, Growth and Photosynthesis by Temperature

1989 ◽  
Vol 37 (4) ◽  
pp. 291 ◽  
Author(s):  
IF Wardlow ◽  
MW Moncur ◽  
CJ Totterdell
Keyword(s):  
Low Temperature ◽  
Root System ◽  
Growth And Development ◽  
Lag Time ◽  
Snow Melt ◽  
Optimum Temperature ◽  
Tap Root ◽  
Crown Tissue ◽  
The Mean ◽  
Maximum Temperatures

The germination of seeds of Caltha introloba F. Muell. on water was very slow with a lag time of 40-60 days. The optimum temperature for germination varied from 22-27°C and germination was very poor in the range from 0-15°C. Stratification of seeds at low temperature (1-2°C) for a period of 4 months, or treatment of the seeds with 3 × 10-4M GA3, more than halved the lag time for germination and considerably enhanced both the rate of germination and the extent of germination under low tempera- ture (0-15°C) conditions. It was concluded that C. introloba seed shed in the summer is unlikely to germinate in the short alpine herb field areas until after snow melt in the following spring. The optimum temperature for both growth and photosynthesis was approximately 15°C, which is close to the mean maximum temperatures for the summer months. Active photosynthesis however was observed at 0°C and therefore could occur throughout the year, except when the plants are covered by snow. Two important features in the establishment and growth of C. introloba appear to be the develop- ment of a deeply penetrating tap root system and the accumulation of carbohydrate reserves in the leaves and crown tissue.

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