Simulating Root Density Dynamics and Nitrogen Uptake – Can a Simple Approach be Sufficient?

The modeling of root growth in many plant–soil models is simple and with few possibilities to adapt simulated root proliferation and depth distribution to that actually found with different crop species. Here we propose a root model, developed to describe root growth, root density and nitrogen uptake. The model focuses on annual crops, and attempts to model root growth of different crop species and row crops and its significance for nitrogen uptake from different parts of the soil volume

Simulating Root Density Dynamics and Nitrogen Uptake -Field Trials and Root Model Approach in Denmark

Plant soil and atmosphere models are commonly used to predict crop yield and associated environmental consequences. Such models often include complex modelling of water movement, soil organic matter turnover and above ground plant growth. However, the root modelling in these models is often very simple, partly due to a limited access to experimental data. Here we propose a root model developed to describe root growth, root density and nitrogen uptake. The model focuses on annual crops, and attempts to model root growth of different crop species and row crops and its significance for nitrogen uptake from different parts of the soil volume

Hormonal regulation of wheat growth during hydroponic culture

Hormonal control of root growth has been explored as one means to alleviate the crowding of plant root systems experienced in prototype hydroponic biomass production chambers being developed by the CELSS Breadboard Project. Four plant hormones, or their chemical analogs, which have been reported to selectively inhibit root growth, were tested by adding them to the nutrient solutions on day 10 of a 25 day growth test using spring wheat in hydroponic cultures. Growth and morphological changes is both shoot and root systems were evaluated. In no case was it possible to inhibit root growth without a comparable inhibition of shoot growth. It was concluded that this approach is unlikely to prove useful for wheat

DigR : how to model root system in its environment? 1 - the model

Many models already exist through literature dealing with root system representation, among which pure structure models such as Root Typ (Pagès 2004), SimRoot (Lynch 1997), AmapSim (Jourdan 1997); diffusion PDE models (Bastian 2008; Bonneu 2009) and structure/function that are rather scarce and recent (Dupuy 2010)may be aroused. Nevertheless in these studies, root architecture modeling was not carried out at organ level including environmental influence and not designed for integration into a whole plant characterization. We propose here a multidisciplinary study on root system from field observations, architectural analysis, formal and mathematical modeling and finally software simulation. Each speciality is individually investigated through an integrative and coherent approach that leads to a generic model (DigR) and its software simulator that is designed for further integration into a global structure/function plant model. DigR model is based on three main key points: (i) independent root type identification (ii) architectural analysis and modeling of root system at plant level; (iii) root architecture setup indexed on root length. Architecture analysis (Barthelemy 2007) applied to root system (Atger 1994) leads to root type organisation for each species. Roots belonging to a particular type share dynamical and morphological characteristics. Root architectural setup consists in topological features as apical growth, lateral branching, senescence and death, and geometrical features as secondary growth and axes spatial positioning. These features are modeled in DigR through 23 parameters whose values can evolve as a function of length position along the root axes for each root type. Topology rules apical growth speed, delayed growth, death and self pruning probabilities. Branching is characterized by spacing and mixture of lateral root types. Geometry rules root diameter increase, branching and growth directions (including local deviations and global reorientation). DigR simulator provides a user interface to input parameter values specific to each species. It is integrated into the Xplo environment (Taugourdeau 2010). Its internal multi-scale memory representation is ready for dynamical 3D visualization, statistical analysis and saving to standard formats (MTG(Godin 2007), Obj,). DigR is simulated in a quasiparallel computing algorithm and may be used either as a standalone application or integrated in other simulation platforms. This will allow further implementation of functional - structural interactions during growth simulation. The software is distributed under free LGPL license and is dedicated both to biologists and modelers. Shown applications (fig. 1) mimic the diversity of root systems and emphasize the genericity of the model according to different sets of parameter values. Examples (fig. 2) prove that additional knowledge may be plugged to DigR to simulate root plasticity facing environmental constraints. Further work will be carried out to apply DigR to various species and to connect DigR to biophysical soil models (Gérard 2008; Zhang et al. 2002); to aerial part models (Barczi 2008); to ecophysiological models (Mathieu 2009, Bornhoffen 2007); and finally to mix this pure descriptive model to a PDE model that handles fine root diffuse modelling (Bonneu 2009). (Texte intégral

Root disturbance and washing effects on shoot and root growth in four plant species : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science at Massey University

Bare-rooting techniques have been widely use in New Zealand nursery production for the preparation of live plants for export to overseas or domestic markets. Bare-root transplants can fail quality requirements due to death or deterioration of regrowth following repotting. The potential for improving bare-root nursery stock quality has prompted study of the morphological effects of removed medium treatment on plant. Two experiments were conducted to explore the effects of physical root disturbance by shaking and washing on the growth and development of camellia (Camellia x saluenensis cv. 'Donation'), pittosporum (Pittosporum tenuifolium cv. 'Kohuhu'), pumpkin (Cucurbita pepo cv. 'Crown Hybrid'), and coleus (Coleus blumei). The shaken plants in both dry and wet conditions suffered a reduction in the growth rate of their leaves compared to the unshaken controls. Root washing influenced the vegetative growth of four species and reproductive growth of pumpkin. The two woody species were more sensitive to treatment stress. Very short time of washing (three seconds) affected camellia bud break and new shoot growth, and inhibit pittosporum root and shoot growth. Similar effects were not sosevered in coleus and pumpkin

Modelling root distribution and nitrogen uptake

Plant soil and atmosphere models are commonly used to predict crop yield and environmental consequence. Such models often include complex modelling modules for water movement, soil organic matter turnover and, above ground plant growth. However, the root modelling in these models are often very simple, partly due to a limited access to experimental data. We present a two-dimensional model for root growth and proliferation. The model focuses on annual crops, and attempt to model root growth of the crops and its significance for N uptake from different parts of the soil volume

Root architecture of two sorghum varieties differ than drought stress tolerance : [Abstract, P 7.17]

Root architecture of two sorghum varieties, fitted in #Durra race# and with different response in drought conditions, has been studied on hydroponic system, pot and in situ on field. These varieties have similar aerial agro-morphological characteristics in optimal growth conditions. In pre-flowering drought stress condition, tolerant variety (SSM1611), has a stable and higher yield than the non-tolerant one (IS16101). On hydroponics conditions and pot growth, varieties are studied at young stage. On field, observations concerned the whole plant cycle. Frequent observations of the aerial system have been made in all the trials, with counting of emerged leaves number and measuring stem height. Adventitious roots number and adventitious roots ranks number have been daily observed on hydroponic system and observations was not destructive. Spatial root disposition on stem was observed on hydroponic condition. On pot and field, these observations were destructive and realised once a week. Adventitious root and their different regions growth (basal none branched region, branched region, apical none branched region) were studied in hydroponic system and in pot. The distribution of the root length density according depth in situ condition was studied using passage model from root impacts to length density. Results show that, the development and the growth of aerial system are practically similar for both of varieties whatever trials conditions. However, for the root system there are some differences in favour of the drought stress tolerant varieties (SSM1611). All the trials showed that, SSM1611 presents a higher adventitious roots number and adventitious roots ranks number than IS16101. Adventitious roots number per rank varies according to the rank and the variety. The distribution of the adventitious roots around the stem seems to be leaded by the same low. Adventitious root of the same rank are balanced distribution around the stem. Until three roots per adventitious root rank, adventitious roots of two successive ranks are distributed in a complementary way around the stem. The growth of adventitious roots and their different regions ((basal none branched region, branched region, apical none branched region)e) present similarity for both of varieties. On hydroponic system, adventitious root length increase first time and then stop their growth to maximal level. However in pot, adventitious root growth seems to bee unlimited. SSM1611 variety reveals a root length density according to depth more important than IS16101 variety one in field. Adventitious roots number, adventitious roots ranks number, and root length density could constitute pertinent and easily accessible drought stress tolerance criterions. (Texte intégral

Tapping into the maize root microbiome to identify bacteria that promote growth under chilling conditions

Background When maize (Zea mays L.) is grown in the Northern hemisphere, its development is heavily arrested by chilling temperatures, especially at the juvenile phase. As some endophytes are beneficial for plants under stress conditions, we analyzed the impact of chilling temperatures on the root microbiome and examined whether microbiome-based analysis might help to identify bacterial strains that could promote growth under these temperatures. Results We investigated how the maize root microbiome composition changed by means of 16S rRNA gene amplicon sequencing when maize was grown at chilling temperatures in comparison to ambient temperatures by repeatedly cultivating maize in field soil. We identified 12 abundant and enriched bacterial families that colonize maize roots, consisting of bacteria recruited from the soil, whereas seed-derived endophytes were lowly represented. Chilling temperatures modified the root microbiome composition only slightly, but significantly. An enrichment of several chilling-responsive families was detected, of which the Comamonadaceae and the Pseudomonadaceae were the most abundant in the root endosphere of maize grown under chilling conditions, whereas only three were strongly depleted, among which the Streptomycetaceae. Additionally, a collection of bacterial strains isolated from maize roots was established and a selection was screened for growth-promoting effects on juvenile maize grown under chilling temperatures. Two promising strains that promoted maize growth under chilling conditions were identified that belonged to the root endophytic bacterial families, from which the relative abundance remained unchanged by variations in the growth temperature. Conclusions Our analyses indicate that chilling temperatures affect the bacterial community composition within the maize root endosphere. We further identified two bacterial strains that boost maize growth under chilling conditions. Their identity revealed that analyzing the chilling-responsive families did not help for their identification. As both strains belong to root endosphere enriched families, visualizing and comparing the bacterial diversity in these communities might still help to identify new PGPR strains. Additionally, a strain does not necessarely need to belong to a high abundant family in the root endosphere to provoke a growth-promoting effect in chilling conditions

Sugarcane root system depth in three different countries

THE SUGARCANE root system depth is crucial as it determines the potential depth of soil available for water and nutrient uptake by the crop. It was reported in an early publication that these roots could grow quite deep (6 m), but otherwise very little data are available on the root system depth. The present study was carried out in three countries: Côte d'Ivoire (var. NCo376), Brazil (var. RB72454) and Réunion, France (var. R570) at various sugarcane growth stages. There were no shoot or root growth constraints (deep soil with enough water). For plant cane, the root front growth (RF in cm) was linear. In Côte d'Ivoire, from 45 to 160 days after planting (DAP), RF = 0.81 DAP; R2 = 0.91. On the island of Réunion, from 100 to 280 DAP, sugarcane root front growth was: RF = 0.56 DAP; R2 = 0.70. When DAP was replaced by thermal time (TT: sum of degree-days), the root front growth patterns were quite similar in Réunion and Côte d'Ivoire (RF = 0.045 and 0.049 TT, respectively). In ratoon conditions, RF was stable when roots from the previous cycle were still in the soil at the onset of the cropping season. Thus, the observed root depth was approximately 4 m in Brazil and Réunion, even though the environment and cultivars were different. These findings showed that, when there is no marked crop growth constraint, roots of modern commercial sugarcane varieties can grow to depths of about 4 m in ratoon crops. While these values were lower than those reported in previous studies, they were higher than those generally accepted at present. (Résumé d'auteur

Some effects of boron to the growth and chemical composition of sainfoin (Onobrychis viciaefolia scop.) : a thesis presented in partial fulfilment of the requirmeents for the degree of Master of Agricultural Science in Plant Science at Massey University, Palmerston North, New Zealand

Some effects of boron on the growth and chemical composition of sainfoin (Onobrychis viciaefolia Scop.) plants cv Fakir were evaluated in a glasshouse. The growth and development of sainfoin plants was not affected by the different levels of boron applied but was affected by nitrogen application and inoculation due to the nodulation failure of the latter. Generally, the root showed the highest dry matter yield and the fastest relative growth rate. Similarly, the total nonstructural carbohydrates of the sainfoin plants were not affected by the different levels of boron. Nitrogen application reduced the total nonstructural carbohydrates of the whole plant. Moreover, when 1 ppm boron was applied, both the shoot and the root yielded the highest total nonstructural carbohydrates. Likewise, root and shoot total nonstructural carbohydrates were reduced by the application of nitrogen. Roots gave a higher total nonstructural carbohydrate yield than the shoot. Boron content of the whole sainfoin plant, the shoot and the root ranging from 0-55 µg/g increased in proportion with the increment of boron applied. Similar results were obtained from boron uptake of the whole plant, the shoot and the root. There was a depression of boron concentrations and boron uptake of the whole plant, the shoot and the root, when nitrogen was applied, implying a deficiency situation. Although nonsignificant effects of boron levels were obtained from nitrogen and phosphorus concentration and uptake, respectively, of both shoot and root, application of 2 ppm boron reduced the concentration of nitrogen but not nitrogen uptake, and reduced phosphorus concentration and phosphorus uptake. Application of nitrogen increased shoot and root nitrogen contents and nitrogen uptake but decreased root and shoot phosphorus concentrations and phosphorus uptake. It was concluded that levels of 2 ppm boron concentration were not adequate to support satisfactory growth when plants were supplied with sufficient levels of other nutrients. Keywords: Boron, nitrogen, Rhizobium, total nonstructural carbohydrates (TNC