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This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact

Science: general issues --- Botany & plant sciences --- plant development --- root system architecture --- lateral root --- pericycle --- branching --- morphogenesis

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Allelopathy refers to the influence of an organism on the growth or development of another. This natural phenomenon mainly takes place in the soil by a biochemical mechanism called exudation. Rye (Secale cereale L.) is commonly known for its allelopathic potential and largely used as a cover crop. For that reason, it has been chosen as plant model for this study. On the other hand, pigweed (Amaranthus retroflexus L.) causes extent losses on crop yields, such as many other weeds encountered in all types of agroecosystems.
First, the interaction between the two plants were investigated through complex culture system and neighborhoods. Biological observations show two very distinct trends of rye morphology towards the growing environment. Indeed, facing the experimental conditions, the aboveground features of rye remained relatively constant whereas the belowground characteristics largely varied.
Secondly, the biological activity of rye raw extract was tested directly on pigweed. Even though germination and survival rate were globally not influenced, the biological essays gave a glimpse on how pigweed seeds and seedlings could react to rye presence in natural conditions.
Thirdly, the allelochemical content of rye root exudates was analyzed. Two benzoxazinoids are mostly known to take part in poaceous allelopathy: DIMBOA and DIBOA. Manifestly, only DIBOA was revealed in rye’s exudates, regardless of the plant present next to it during its growth.
Lastly, the VOCs emission of rye root was also studied. A specific experimental device allowed the extraction of VOCs directly from the rye rhizosphere. Several biogenic compounds were detected but very few of them are already listed for presumed allelopathic activities. This aspect of this work opens the door towards a whole new field in the study of volatile plant metabolites.
To conclude, viewing the actual environmental context, more sustainable agronomic practices are urgently required. Allelopathy might be one the key for better weed management as long as plant interactions with their surrounding are well understood. This work contributes to a better comprehension of the war that is taking place underground.

Allelopathy --- Secale cereale --- Amaranthus retroflexus --- Benzoxazinoids --- VOC --- root system --- Sciences du vivant > Agriculture & agronomie

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Nutrient Signalling --- Root System Architecture (RSA) --- Modelling Biological Systems --- Roots --- Nutrient Uptake --- Modelling Transport Processes --- Ion Transport

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In the earlier monograph Pseudo-reductive Groups, Brian Conrad, Ofer Gabber, and Gopal Prasad explored the general structure of pseudo-reductive groups. In this new book, Classification of Pseudo-reductive Groups, Conrad and Prasad go further to study the classification over an arbitrary field. An isomorphism theorem proved here determines the automorphism schemes of these groups. The book also gives a Tits-Witt type classification of isotropic groups and displays a cohomological obstruction to the existence of pseudo-split forms. Constructions based on regular degenerate quadratic forms and new techniques with central extensions provide insight into new phenomena in characteristic 2, which also leads to simplifications of the earlier work. A generalized standard construction is shown to account for all possibilities up to mild central extensions. The results and methods developed in Classification of Pseudo-reductive Groups will interest mathematicians and graduate students who work with algebraic groups in number theory and algebraic geometry in positive characteristic.

Linear algebraic groups. --- Group theory. --- Geometry, Algebraic. --- Algebraic geometry --- Geometry --- Groups, Theory of --- Substitutions (Mathematics) --- Algebra --- Algebraic groups, Linear --- Geometry, Algebraic --- Group theory --- Algebraic varieties --- "ient homomorphism. --- Cartan k-subgroup. --- Dynkin diagram. --- Isogeny Theorem. --- Isomorphism Theorem. --- Levi subgroup. --- SeveriЂrauer variety. --- Tits classification. --- Tits-style classification. --- Weil restriction. --- algebraic geometry. --- automorphism functor. --- automorphism scheme. --- automorphism. --- canonical central extensions. --- central "ient. --- central extension. --- characteristic 2. --- conformal isometry. --- degenerate quadratic form. --- double bond. --- exotic construction. --- field-theoretic invariant. --- generalized exotic group. --- generalized standard group. --- generalized standard presentation. --- generalized standard. --- isomorphism class. --- isomorphism. --- isotropic group. --- k-tame central extension. --- linear isomorphism. --- linear-algebraic invariant. --- maximal torus. --- minimal type. --- non-reduced root system. --- number theory. --- pseudo-isogeny. --- pseudo-reductive group. --- pseudo-semisimple group. --- pseudo-simple group. --- pseudo-simple k-group. --- pseudo-split form. --- pseudo-split. --- quadratic space. --- quadrics. --- rank-1. --- rank-2. --- rigidity property. --- root field. --- root system. --- scheme-theoretic center. --- semisimple "ient. --- semisimple k-group. --- structure theorem.

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The impacts of climate change on crop production are already a reality in Europe and across the rest of the world. In order to mitigate these impacts, access to unexploited genetic crop diversity for the production of new varieties that can thrive in more extreme environmental conditions is of prime importance. Herein, genetic diversity should provide the raw materials for breeding and plant improvements. Despite the vast pool of resources that exist, much of the germplasm richness found in gene banks is poorly documented. To overcome the barriers between germplasm conservation and use, a complete evaluation is necessary to determine the useful diversity they contain.This Special Issue focuses on “Old Germplasm for New Needs: Managing Crop Genetic Resources”. We gathered novel research, reviews, and opinion pieces covering all related topics, including germplasm evaluation, crop genetics and improvements, novel crops, phenotyping, physiological responses of inbred lines, management solutions, modeling, case studies from the field, and policy positions.

aromatic rice --- local variety --- gelatinization temperature --- badh2-E7 allele --- population structure --- Criollo cacao --- microsatellites --- genetic purity --- Central America --- Axiom 35K Wheat Breeders array --- genetic diversity --- wheat genotyping --- Solanum lycopersicum --- agro-biodiversity --- crops --- breeding --- DNA markers --- black soybean --- green cotyledon --- anthocyanin --- chlorophyll --- Lactuca sativa L. --- crisphead --- oak-leaf --- root system architecture --- tipburn --- nutritional imbalance --- breeding lines --- landraces --- phenotypic traits --- molecular markers --- almond descriptors --- conservation --- endangered cultivars --- fruit quality --- genetic resources --- Prunus dulcis --- MTSI --- multi-environment --- soybean --- seed compositions --- WAASB --- barley --- germplasm --- Hordeum vulgare --- landrace --- DArTseq --- anthocyanins --- black carrot --- bolting --- flavonoids --- glasshouse cultivation --- leaf --- nutrient analysis --- taproot --- n/a