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1.
Soil compaction and the architectural plasticity of root systems.
Correa, J, Postma, JA, Watt, M, Wojciechowski, T
Journal of experimental botany. 2019;(21):6019-6034
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Abstract
Soil compaction is a serious global problem, and is a major cause of inadequate rooting and poor yield in crops around the world. Root system architecture (RSA) describes the spatial arrangement of root components within the soil and determines the plant's exploration of the soil. Soil strength restricts root growth and may slow down root system development. RSA plasticity may have an adaptive value, providing environmental tolerance to soil compaction. However, it is challenging to distinguish developmental retardation (apparent plasticity) or responses to severe stress from those root architectural changes that may provide an actual environmental tolerance (adaptive plasticity). In this review, we outline the consequences of soil compaction on the rooting environment and extensively review the various root responses reported in the literature. Finally, we discuss which responses enhance root exploration capabilities in tolerant genotypes, and to what extent these responses might be useful for breeding. We conclude that RSA plasticity in response to soil compaction is complex and can be targeted in breeding to increase the performance of crops under specific agronomical conditions.
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Kinetic growth model for hairy root cultures.
Katuri, SR, Khanna, R
Mathematical biosciences and engineering : MBE. 2019;(2):553-571
Abstract
The growth of hairy root cultures in bioreactors yields a complex root network and limits nutrient availability to the inner core of the root bed. A kinetic growth model to explain the growth in terms of length of individual primary and their higher order branches has been developed. The external transport of nutrient modeled based on mass transfer rate of limiting nutrient across root surface and internal transport of nutrient modeled based on flow of nutrient from primary to secondary roots. The growth reaction constant during elongation phase, which is function of limiting nutrient concentration found to be in the range of 0.1 to 0.4 d⁻¹ for various species through fitting. The model equations are well fitted with the experimental data with minimum root mean square error for the ratio of radius of primary to secondary root is 1.5, the nutrient to biomass ratio in the range 1.5 to 4.0 and the inter node distance is the range of 0.2 to 0.5 cm. Higher growth coefficients, smaller inter node distances yields large number of tips and higher growth of primary and secondary roots. Higher growth coefficient can be achieved by manipulating nutrient medium concentration and cells reach branching age faster which alters the inter-node distance and branching rate. This model will be a crucial input to estimate packing fraction and local concentration profile in the growing hairy root bed in bioreactors.
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The Nutritional Value and Biological Activity of Concentrated Protein Fraction of Potato Juice.
Kowalczewski, PŁ, Olejnik, A, Białas, W, Rybicka, I, Zielińska-Dawidziak, M, Siger, A, Kubiak, P, Lewandowicz, G
Nutrients. 2019;(7)
Abstract
Potato protein is recognized as one of the most valuable nonanimal proteins due to the high content of essential amino acids. So far, it has not been used in human nutrition on a large scale due to technological limitations regarding its acquisition. In this study, the protein fraction of potato juice was concentrated with the use of membrane separation. The obtained potato juice protein concentrate (PJPC) was characterized in terms of nutritional value and biological activity, and the amino acid composition, mineral content, and antioxidant properties were determined. Moreover, in vitro cytotoxic activity against cancer cells of the gastrointestinal tract was investigated. The results of the present study indicate that PJPC is an excellent source of lysine and threonine, while leucine is its limiting amino acid, with an amino acid score (AAS) of 65%. Moreover, PJPC contains substantial amounts of Fe, Mn, K, and Cu. As demonstrated experimentally, PJPC is also characterized by higher antioxidant potential than potato itself. Biological activity, however, is not limited to antioxidant activity alone. Cytotoxicity studies using a gastric cancer cell line (Hs 746T), a colon cancer cell line (HT-29), and human colon normal cells (CCD 841 CoN) proved that PJPC is characterized by selective activity against cancer cells. It can thus be concluded that the developed method of producing protein concentrate from potato juice affords a product with moderate nutritional value and interesting biological activity.
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4.
Curcuma longa L. ameliorates asthma control in children and adolescents: A randomized, double-blind, controlled trial.
Manarin, G, Anderson, D, Silva, JME, Coppede, JDS, Roxo-Junior, P, Pereira, AMS, Carmona, F
Journal of ethnopharmacology. 2019;:111882
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Roots of Curcuma longa L. are used as medicine for millennia. They possess several pharmacological properties, including anti-inflammatory action, and can be suitable for asthma treatment. AIM OF THE STUDY We aimed to test the hypothesis that, in children and adolescents with persistent asthma, the administration of powdered roots of C. longa for 6 months, in addition to standard treatment, compared to placebo, will result in better disease control. PATIENTS AND METHODS We conducted a randomized, double-blind, placebo-controlled, phase II clinical trial. Patients were randomly assigned to receive 30 mg/kg/day of C. longa for 6 months, or placebo. Data were collected prospectively. All patients were categorized for asthma severity and control according to GINA-2016 and underwent pulmonary function tests. RESULTS Overall, both groups experienced amelioration of their frequency of symptoms and interference with normal activity, but no differences were found between the two treatment groups. However, patients receiving C. longa experienced less frequent nighttime awakenings, less frequent use of short-acting β-adrenergic agonists, and better disease control after 3 and 6 months. CONCLUSION The powdered roots of C. longa led to less frequent nighttime awakenings, less frequent use of short-acting β-adrenergic agonists, and better disease control after 3 and 6 months, when compared to placebo.
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Engineering root microbiomes for healthier crops and soils using beneficial, environmentally safe bacteria.
Martínez-Hidalgo, P, Maymon, M, Pule-Meulenberg, F, Hirsch, AM
Canadian journal of microbiology. 2019;(2):91-104
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Abstract
The Green Revolution developed new crop varieties, which greatly improved food security worldwide. However, the growth of these plants relied heavily on chemical fertilizers and pesticides, which have led to an overuse of synthetic fertilizers, insecticides, and herbicides with serious environmental consequences and negative effects on human health. Environmentally friendly plant-growth-promoting methods to replace our current reliance on synthetic chemicals and to develop more sustainable agricultural practices to offset the damage caused by many agrochemicals are proposed herein. The increased use of bioinoculants, which consist of microorganisms that establish synergies with target crops and influence production and yield by enhancing plant growth, controlling disease, and providing critical mineral nutrients, is a potential solution. The microorganisms found in bioinoculants are often bacteria or fungi that reside within either external or internal plant microbiomes. However, before they can be used routinely in agriculture, these microbes must be confirmed as nonpathogenic strains that promote plant growth and survival. In this article, besides describing approaches for discovering plant-growth-promoting bacteria in various environments, including phytomicrobiomes and soils, we also discuss methods to evaluate their safety for the environment and for human health.
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Effects of body size and root to shoot ratio on foliar nutrient resorption efficiency in Amaranthus mangostanus.
Peng, H, Yan, Z, Chen, Y, Zhao, X, Han, W
American journal of botany. 2019;(3):363-370
Abstract
PREMISE OF THE STUDY Nutrient resorption is essential for plant nutrient conservation. Large-bodied plants potentially have large nutrient sink pools and high nutrient flux. Whether and how nutrient resorption can be regulated by plant size and biomass allocation are yet unknown. METHODS Using the herbaceous plant Amaranthus mangostanus in greenhouse experiments for two consecutive years, we measured plant biomass, height, and stem diameter and calculated the root to shoot biomass ratio (R/S ratio) and nutrient resorption efficiency (NuRE) to assess the effects of plant body size and biomass allocation on NuRE. NuRE was calculated as the percentage reduction in leaf nutrient concentration from green leaf to senesced leaf. KEY RESULTS NuRE increased with plant biomass, height, and stem diameter, suggesting that the individuals with larger bodies, which led to a larger nutrient pool, tended to resorb proportionally more nutrients from the senescing leaves. NuRE decreased with increasing root to shoot ratio, which might have reflected the nutrient acquisition trade-offs between resorption from the senescent leaves and absorption from the soil. Increased root biomass allocation increased the proportion of nutrient acquisition through absorption more than through resorption. CONCLUSIONS This study presented the first experimental evidence of how NuRE is linked to plant size (indicated by biomass, height, and stem diameter) and biomass allocation, suggesting that nutrient acquisition could be modulated by the size of the nutrient sink pool and its partitioning in plants, which can improve our understanding of a conservation mechanism for plant nutrients. The body size and root to shoot ratio effects might also partly explain previous inconsistent reports on the relationships between environmental nutrient availability and NuRE.
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7.
A gene regulatory network for root hair development.
Shibata, M, Sugimoto, K
Journal of plant research. 2019;(3):301-309
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Abstract
Root hairs play important roles for the acquisition of nutrients, microbe interaction and plant anchorage. In addition, root hairs provide an excellent model system to study cell patterning, differentiation and growth. Arabidopsis root hairs have been thoroughly studied to understand how plants regulate cell fate and growth in response to environmental signals. Accumulating evidence suggests that a multi-layered gene regulatory network is the molecular secret to enable the flexible and adequate response to multiple signals. In this review, we describe the key transcriptional regulators controlling cell fate and/or cell growth of root hairs. We also discuss how plants integrate phytohormonal and environmental signals, such as auxin, ethylene and phosphate availability, and modulate the level of these transcriptional regulators to tune root hair development.
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The evolution of root branching: increasing the level of plasticity.
Motte, H, Beeckman, T
Journal of experimental botany. 2019;(3):785-793
Abstract
Plant roots and root systems are indispensable for water and nutrient foraging, and are a major evolutionary achievement for plants to cope with dry land conditions. The ability of roots to branch contributes substantially to their capacity to explore the soil for water and nutrients, and led ~400 million years ago to the successful colonization of land by plants, eventually even in arid regions. During this colonization, different forms of root branching evolved, reinforcing step by step the phenotypic plasticity of the root system. Whereas the lycophytes, the most ancient land plants with roots, only branch at the root tip, ferns are able to form roots laterally in a fixed pattern along the main root. Finally, roots of seed plants show the highest phenotypic plasticity, because lateral roots can possibly, dependent on internal and/or external signals, be produced at almost any position along the main root. The competence to form lateral roots in seed plants is based on the presence of internal cell files with stem cell-like features. Despite the dissimilarities between the different clades, a number of genetic modules seem to be co-opted in order to acquire root branching capacity. In this review, starting from the lateral root pathways in seed plants, we review root branching in the different land plant lineages and discuss the hitherto described genetic modules that contribute to their root branching capacity. We try to obtain insight into how land plants have acquired an increasing root branching plasticity during evolution that contributed to the successful colonization of our planet by seed plants.
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Tackling Plant Phosphate Starvation by the Roots.
Crombez, H, Motte, H, Beeckman, T
Developmental cell. 2019;(5):599-615
Abstract
Plant responses to phosphate deprivation encompass a wide range of strategies, varying from altering root system architecture, entering symbiotic interactions to excreting root exudates for phosphorous release, and recycling of internal phosphate. These processes are tightly controlled by a complex network of proteins that are specifically upregulated upon phosphate starvation. Although the different effects of phosphate starvation have been intensely studied, the full extent of its contribution to altered root system architecture remains unclear. In this review, we focus on the effect of phosphate starvation on the developmental processes that shape the plant root system and their underlying molecular pathways.
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Tolerance of roots to low oxygen: 'Anoxic' cores, the phytoglobin-nitric oxide cycle, and energy or oxygen sensing.
Armstrong, W, Beckett, PM, Colmer, TD, Setter, TL, Greenway, H
Journal of plant physiology. 2019;:92-108
Abstract
Acclimation by plants to hypoxia and anoxia is of importance in various ecological systems, and especially for roots in waterlogged soil. We present evidence for acclimation by roots via 'anoxic' cores rather than being triggered by O2 sensors. The evidence for 'anoxic' cores comes from radial O2 profiles across maize roots and associated metabolic changes such as increases in the 'anaerobic enzymes' ADH and PDC in the 'anoxic' core, and inhibition of Cl- transport to the xylem. These cores are predicted to develop within 15-20 min after sudden transfer of a root to hypoxia, so that the cores are 'anoxically-shocked'. We suggest that 'anoxic' cores could emanate a signal(s), such as ACC the precursor of ethylene and/or propagation of a 'Ca2+ wave', to other tissue zones. There, the signalling would result in acclimation of the tissues to energy crisis metabolism. An O2 diffusion model for tissues with an 'anoxic' core, indicates that the phytoglobin-nitric oxide (Pgb-NO) cycle would only be engaged in a thin 'shell' (annulus) of tissue surrounding the 'anoxic' core, and so would only contribute small amounts of ATP on a whole organ basis (e.g. whole roots). A key feature within this annulus of tissue, where O2 is likely to be limiting, is that the ratio (ATP formed) / (O2 consumed) is 5-6, both when the NAD(P)H of glycolysis is converted to NAD(P)+ by the Pgb-NO cycle or by the TCA cycle linked to the electron transport chain. The main function of the Pgb-NO cycle may be the modulating of NO levels and O2 scavenging, thus preventing oxidative damage. We speculate that an 'anoxic' core in hypoxic plant organs may have a particularly high tolerance to anoxia because cells might receive a prolonged supply of carbohydrates and/or ATP from the regions still receiving sufficient O2 for oxidative phosphorylation. Severely hypoxic or 'anoxic' cores are well documented, but much research on responses of roots to hypoxia is still based on bulk tissue analyses. More research is needed on the interaction between 'anoxic' cores and tissues still receiving sufficient O2 for oxidative phosphorylation, both during a hypoxic exposure and during subsequent anoxia of the tissue/organ as a whole.