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Root system architecture of cedar seedlings growing on five media with different hydromechanical constraints: (a) Hyd, (b) Ver, (c) Saw, (d) VGr, and (e) San. The scale bar corresponds to 5 cm.
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The biomechanical root flexibility in response to hydromechanical soil heterogeneity is the most determining factor of the root architecture which plays a paramount role in mycorrhizal infection and allows the seedlings to adapt to the environmental constraint. We examined the impact of five different hydromechanical medium properties (hydroponics,...
Citations
... The soil organic matter plays a paramount role in the soil properties by affecting soil aggregation and biochemical characteristics (Mangalassery et al., 2019;El Amrani and Bendriss Amraoui, 2020); favouring nutrient retention and cycling (Molina-Herrera and Romanyà, 2015); affecting soil microbial activity and constitutes a nitrogen tank for the coniferous forest soil Zhang et al., 2018;El Amrani and Bendriss Amraoui, 2022). The nitrogen is one of the most important nutrients for plants it affects their functions from cell metabolism to growth (Boukcim et al., 2006;Saiz-Fernández et al., 2015). ...
The organic matter constitutes the most important source of nitrate and ammonium in coniferous forest soil, which are the two major nitrogen forms used by plants. The preference and/or adaptation of one N-form over another by seedlings genotypes is a determinant factor in the success of reforestation programs, not only for cedar species but any other forest essence. In a controlled growth chamber, the seedlings of two provenances of Cedrus atlantica M. (Gouraud and Moudmame) are grown on natural soil or on organic matter fertilized with different N-form and concentration. Our results show a high nitrogen requirement and a different preference towards nitrogen forms which is mainly manifested at secondary roots. On the other hand, variations in the cotyledons affect the growth and the response of the seedlings to the nitrogen form and thus reveal different forms of adaptation to nitrogen nutrition which are linked to the cotyledons and to the age of seedlings. The growth response of C. atlantica to nitrogen form and concentration is discussed in light of the effect of the provenance and cotyledons. Taken together, these results suggest that knowledge of the nitrogen requirements of the different genotypes of C. atlantica at the juvenile stage could be a good tool for successful reforestation of this forest species.
... This beneficial effect of the root microbiota on plants is achieved by the secretion of different growth hormones such as auxin, cytokinin and gibberellic acid, or by reducing the production of ethylene. This leads to the promotion of plant growth by changing the architecture of the root system (Shekhar et al., 2019;El Amrani, Amraoui, 2020) and also by increasing the acquisition of nutrients (Fitzpatrick et al., 2018). ...
Soil microbial communities play a key role in the evolution of the rhizosphere. In addition, proper exploration of these microbial resources represents a promising strategy that guarantees the health and sustainability of all ecosystems connected to the ground. Under the influence of environmental conditions, microbial communities can change compositions in terms of abundance and diversity. Beyond the descriptive level, the current orientation of microbial ecology is to link these structures to the functioning of ecosystems; specifically, to understand the effect of environmental factors on the functional structure of microbial communities in ecosystems. This review focuses on the main interactions between the indigenous soil microflora and the major constituents of the rhizosphere to understand, on the one hand, how microbial biodiversity can improve plant growth and maintain homeostasis of the rhizospheric ecosystem, on the other hand, how the maintenance and enrichment of plant biodiversity can contribute to the conservation of soil microbial diversity; knowing that these microorganisms are also controlled by the abiotic properties of the soil. Overall, understanding the dynamics of the rhizosphere microbiome is essential for developing innovative strategies in the field of protecting and maintaining the proper functioning of the soil ecosystem.
... e capacity of trees to survive aridity depends on a group of physiological and morphological changes including stomatal closure [76], inhibition of shoot growth [77], and reduction of root longevity [78]. Similarly, EL Amrani and Bendriss Amraoui [79] have recently found that the continuous and partial mechanical barriers combined with the low availability of water reduce the aerial part growth and the main root length of C. atlantica seedlings. Studies on anatomical adaptation to drought were made by Kivimäenpää et al. [80] on Norway spruce needles vascular cylinder area. ...
... In Mediterranean ecosystems, water availability plays an important role in determining phenological development [83]. In the present study, the length of needle (Nl), the width of vascular bundle including endodermis (Bw), and the thickness of wall of hypodermis cell (Ht) which were the highest discriminating characters between populations of the Middle and High Atlas and between populations of the Middle Atlas are important longer-term adaptations to semiarid climate. is acclimatization prevents evapotranspiration by increasing Ht and reducing Nl and favors needle water transfer by increasing Bw (Table 2). is observation is in agreement with the study of EL Amrani and Bendriss Amraoui [79] who found an increase of root phloem and xylem areas in the existence of mechanical impedance combined with the low availability of water. ese traits may be powerful tools to select individuals genotypically adapted to drought conditions, particularly in the arid area-Sahara mountains of Algeria in which Allen et al. [72] reported that the recent C. atlantica mortality began as small patches on drier aspects, eventually coalescing into large patches affecting all ages on all exposures. ...
Atlas cedar (Cedrus atlantica (Endl.) G. Manetti ex Carrière) is an endemic species in the mountains of North Africa that is attracting international interest in its use in the reforestation of degraded ecosystems. is study aims to investigate and evaluate the morphoanatomical characteristics of needles of four cedar populations localized in the Middle and High Atlas Mountains. Descriptive statistics, analysis of variance (ANOVA), descriptive power, scatter-plot of the discrimination function, scatter-plot of discrimination, and dendrogram of the closest Euclidean distances were made on traits. e results of the linear model of ANOVA nested as population and tree within population suggest the differences statistically significant for the traits measured at a different level. Among these traits, the length of the needle, the width of a vascular bundle including endodermis, and thickness of the wall of hypodermis cell revealed the highest discriminating characters among populations of C. atlantica from the Middle and High Atlas and between the populations of the Middle Atlas. e agglomeration of populations over short Euclidean distances also showed a higher level of differentiation between two ecotypes of C. atlantica not very geographically distant in the Atlas Mountains of Morocco. e ecotype belonging to Aït Oufella and Aït Ayach confers this species a place of choice in the projects of revalorization of the Mediterranean populations, especially in semiarid areas.
Plants, as immobile organisms, depend on their roots to access soil resources efficiently and cost‐effectively. To achieve this goal, maximize productivity, and adapt to variable challenging conditions, plants rely on root phenotypic plasticity. This includes changes in root morphology, growth angles, diameter, elongation, branching density, and turnover rate. In simple terms, a plant root system is a dynamic structure that can change its branching structure in response to changes in biotic and abiotic conditions such as water availability, soil mineral nutrient content, soil compaction, salinity, and the formation of symbiotic relationships with other organisms or anchored in the substrate. However, the complexity of these responses and their impact on plant fitness are not well understood. In this paper, we review different aspects of the morphological plasticity of the root system. The results show that root flexibility can greatly support plant adaptation and control the nature of plant–plant interactions within the population. Thus, gaining a comprehensive understanding of root plasticity can lead to improved and sustainable plant production. We discuss the morphological plasticity of plant root systems in response to various biotic and abiotic factors, such as water availability, soil nutrient content, compaction, salinity, plant–plant interactions, and interactions with soil microorganisms. The aspects examined include root morphology, growth angles, diameter, elongation, branching density, and turnover rate. These parameters are crucial in determining how plants adapt to changes in their environment and optimize their growth and productivity.
Introduction : le cèdre de l’Atlas est une espèce endémique de l’Afrique du Nord. Il représente pour le Maroc une essence emblématique de grand intérêt écologique, économique et sociale. La croissance lente de son système racinaire constitue une menace sérieuse pour le re/boisement et la régénération naturelle de cette espèce. Bien que la mycorhization aide les semis du cèdre à développer des racines dans des conditions défavorables nos connaissances sur la mycorhization des plantules de cèdre sont encore fragmentaires.Objectifs : compte tenu de ces difficultés rencontrées par le cèdre aux stades précoces, apparaît la nécessité d'étudier les interactions entre les racines et les facteurs biotiques et abiotiques du sol, ainsi la recherche de solutions pour le bon développement et la mycorhization du système racinaire.Matériel et Méthodes : pour atteindre ces objectifs on a étudié les réponses des plantules, principalement au niveau du système racinaire, aux facteurs physicochimique, textural, hydromécanique et microbiologique du sol ainsi que la réussite de la mycorhization du cèdre aux stades juvénile.Résultats : en réponse à la texture et la physicochimie des sols de cédraies, les plantules de Cedrus atlantica M. montrent une forte dépendance de la teneur en carbone organique, en azote, en phosphore et à la nature granulométrique du sol ; de manière qu’ils stimulent la longueur et le nombre de racines secondaires sur certains sols alors qu’ils permettent d’autres de prédominer au niveau de la croissance des plantules ; soulignent ainsi l’importance des racines secondaires et tertiaires dans la détermination des stratégies de développement de l’architecture racinaire.Les plantules de deux provenances de C. atlantica M. montrent des besoins élevés en azote et une préférence différente vers les formes d’azote qui se manifeste essentiellement au niveau des racines secondaires. D’autre part, les variations au niveau des cotylédons affectent la croissance et la réponse des plantules à la forme d’azote et révèlent ainsi différentes formes d’adaptation vis-à-vis de la nutrition azotée liée aux cotylédons et à l’âge des plantules.Les propriétés hydromécaniques du milieu de culture affectent profondément la morphologie, la physiologie et l'anatomie des racines des plantules de C. atlantica M. de sorte que les conditions extrêmes provoquent soit une surstimulation de l’allongement de la racine principale sans ramification ou une forte réduction de l’allongement de cette racine avec beaucoup de racines latérales réduites. A l’échelle anatomique ces réponses sont plus apparentes au niveau du cortex alors que les vaisseaux conducteurs déterminent la stratégie de croissance adoptée par la plantule face aux conditions hydromécaniques du milieu de culture.Les interactions de la microflore indigène du sol de cédraie présentent un effet déterminant sur la croissance et le développement des plantules de C. atlantica M.. De sorte que la composition microbienne de certains sols stimule la croissance des racines et diminue la densité racinaire, pourtant, la stimulation de l’activité fongique de ce même sol montre un effet négatif. Généralement l’enrichissement du milieu de culture stimule le nombre de racines tertiaires et la densité racinaire, au détriment de la racine principale et des racines secondaires, surtout au niveau des sols défavorables. L’élimination des microorganismes actifs et l’appauvrissement nutritif de 6 provenances de sol de cédraie ont permis le piégeage de 15 espèces de champignons ectomycorhiziens, dont un ectendomycorhize, capable de coloniser les racines des jeunes plantules de C. atlantica M.. Cependant, la faible architecture racinaire reste un problème même après la mycorhization. D’où l’importance cruciale de cette nouvelle gamme de champignons mycorhiziens caractérisés pour la première fois chez les plantules de C. atlantica M. surtout pour les travaux visant l’amélioration de l’état sanitaire des plantules du cèdre.
