Download or read book tude de la contribution des racines la r duction des nitrates written by Alain Gojon and published by . This book was released on 1987 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: LA CONTRIBUTION DES RACINES A LA REDUCTION DU NITRATE PAR DE JEUNES PLANTES DE MAIS ET D'ORGE EST ETUDIEE AU MOYEN DE MARQUAGE **(15)N ET DE MESURES DE L'ACTIVITE DE LA NITRATE REDUCTASE. LES RESULTATS INDIQUENT QUE LES RACINES SONT LE SIEGE PRINCIPAL DE LA REDUCTION DU NITRATE AU COURS DE LA PERIODE D'INDUCTION DE LA NITRATE REDUCTASE. AU CONTRAIRE, LORSQUE CETTE INDUCTION EST ACHEVEE, LE ROLE DES RACINES DEVIENT MINORITAIRE. LA CONTRIBUTION DES RACINES A L'ASSIMILATION DU NITRATE PAR LA PLANTE SEMBLE AUGMENTEE LORSQUE L'AMMONIUM EST ABSENT DU MILIEU NUTRITIF, OU LORSQUE CE DERNIER NE CONTIENT QU'UNE FAIBLE CONCENTRATION DE NITRATE. DANS CE DERNIER CAS, C'EST LA FREINAGE DE L'EXPORTATION DU NITRATE VERS LES PARTIES AERIENNES QUI SEMBLE LIMITER LEUR ASSIMILATION. LA MESURE DE L'INTENSITE DE CETTE LIMITATION DE LA REDUCTION DANS LES PARTIES AERIENNES PAR LE FLUX DE NITRATE QUI LEUR PARVIENT PEUT DONC CONSTITUER UNE APPROCHE INTERESSANTE POUR CARACTERISER LA DISPONIBILITE DU NITRATE DANS LE MILIEU, ET LA CONTRIBUTION DES RACINES A SON ASSIMILATION PAR LA PLANTE

Download or read book ETUDE DE LA CONTRIBUTION DES PARTIES AERIENNES A LA REDUCTION DU NITRATE CHEZ LE PECHER PRUNUS PERSICA L BATSCH written by CLAUDE.. BUSSI and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: LA DISTRIBUTION DE L'ASSIMILATION DE NO#3# ENTRE RACINES ET PARTIES AERIENNES A ETE ETUDIEE CHEZ LE PECHER (PRUNUS PERSICA L. BATSCH) A L'AIDE DE DIFFERENTES METHODES (MESURES D'ACTIVITE NITRATE REDUCTASE, MARQUAGES AU #1#5N ET ANALYSES DE SEVE). LES RESULTATS OBTENUS ABOUTISSENT A LA CONCLUSION D'UNE ASSIMILATION DE NO#3# MAJORITAIREMENT RACINAIRE CHEZ CETTE ROSACEE FRUITIERE. NEANMOINS, ILS SOULIGNENT LA REALITE AGRONOMIQUE DE LA REDUCTION FOLIAIRE DE NO#3# DANS LES CONDITIONS DU VERGER, ET INDIQUENT QUE CETTE REDUCTION PEUT REPRESENTER JUSQU'A 40% DE L'ASSIMILATION TOTALE CHEZ DE JEUNES PLANTS DE PECHER CULTIVES AU LABORATOIRE. LES CAUSES DE LA FAIBLE ACTIVITE ASSIMILATRICE DES PARTIES AERIENNES ONT ETE RECHERCHEES. LES EXPERIENCES DESTINEES A MODULER SPECIFIQUEMENT L'ABSORPTION ET LA REDUCTION DE NO#3# DANS LES RACINES METTENT EN EVIDENCE UN ANTAGONISME MARQUE ENTRE CETTE DERNIERE FONCTION ET L'EXPORTATION DE L'ANION VERS LES PARTIES AERIENNES. LA REDUCTION DE NO#3#, QUI APPARAIT LARGEMENT PRIORITAIRE, AGIT PROBABLEMENT EN LIMITANT LA DIFFUSION RADIALE DE L'ANION VERS LA STELE. CECI ENTRAINE UNE FAIBLE DISPONIBILITE DE NO#3# AUX SITES DE SA SECRETION DANS LE XYLEME, INTERDISANT SON TRANSPORT EN QUANTITE IMPORTANTE VERS LES ORGANES AERIENS. L'AUGMENTATION DE LA VITESSE D'ABSORPTION DE NO#3# STIMULE PROPORTIONNELLEMENT MOINS LA REDUCTION DANS LES RACINES QUE LA SECRETION DE L'ANION DANS LE XYLEME. MAIS, CONTRAIREMENT A CE QUI EST OBSERVE CHEZ LES ESPECES HERBACEES, LES CAPACITES DE PRELEVEMENT DE LA ROSACEE FRUITIERE SONT APPAREMMENT TROP FAIBLES POUR FAIRE EVOLUER LA COMPETITION ENTRE CES DEUX FONCTIONS EN FAVEUR DE LA DERNIERE. LA CULTURE DE JEUNES PECHERS SUR MILIEU NITRIQUE OU AMMONIACAL MONTRE, QUE MEME SI ELLE EST LIMITEE, L'EXPORTATION DE NO#3# VERS LES PARTIES AERIENNES EST ASSOCIEE A UNE MEILLEURE CROISSANCE DE CES ORGANES. DANS NOS EXPERIENCES, CETTE CROISSANCE EST EGALEMENT ETROITEMENT CORRELEE AUX QUANTITES DE CATIONS EXPORTES PAR LES RACINES VERS LES PARTIES AERIENNES. A LA SUITE DE CES OBSERVATIONS, L'HYPOTHESE QUE L'EFFET BENEFIQUE DE LA NUTRITION NITRIQUE SOIT LIE AU ROLE DE NO#3# DANS L'ACCOMPAGNEMENT DES CATIONS EST PLUS PARTICULIEREMENT DISCUTEE. ELLE PERMET D'EXPLIQUER QUE LA MAJORITE DES ESPECES HERBACEES SOIENT PLUS SENSIBLES A LA NUTRITION AMMONIACALE QUE LE PECHER, QUI, DAVANTAGE QUE CES DERNIERES, EST CAPABLE DE REMPLACER PARTIELLEMENT NO#3# PAR SO#4## OU PI DANS LA SEVE DU XYLEME

Download or read book Eighth International Congress of Applied Chemistry written by and published by . This book was released on 1912 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Contribution a l tude de la nutrition azot e et de la fixation symbiotique chez la luzerne Medicago sativa cv Europe written by Mesbah Babalar and published by . This book was released on 1985 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: La Luzerne peut utiliser trois sources d'azote : N2, N03 ̅ et NH4+. La croissance des plantes est augmentée par la présence d'azote nitrique ; pendant les 10 premières semaines, la croissance des plantes N2 est toujours beaucoup plus faible que celle des plantes alimentées avec du nitrate, ou du nitrate et de l'ammonium ; les plantes recevant 4 mM N03 ̅ ont deux fois plus de matière sèche que celles qui en ont 2 mM seulement. Le remplacement de 0,7 mM de nitrate par 0,7 mM d'ammonium dans un mélange (3,3 mM N03 ̅ + 0,7 mM NH4+) n'influence pas la croissance de la plante mais inhibe complètement le développement des nodosités. Le nitrate inhibe aussi la formation des nodosités mais à des doses beaucoup plus élevées que l'ammonium. L'activité nitrate réductase in vivo est présente chez les plantes N2, même quand la germination se fait en absence d'azote nitrique. Tous les organes de la luzerne possèdent l'activité nitrate réductase in vivo, même les tiges qui peuvent contenir 20 % de l'activité totale de la plante. L'activité nitrate réductase existe aussi dans les nodosités. Elle est 5 fois plus élevée dans les feuilles, les tiges et les racines des plantes avec nitrate que dans les mêmes organes des plantes N2. Elle n'augmente, en fonction de la concentration des solutions en nitrate, que dans les racines. Après la coupe des parties aériennes, elle augmente dans tous les organes. L'activité nitrogénase (réduction d'acétylène) par plante est plus élevée chez les plantes N2 que chez celles qui ont du nitrate ou du nitrate et de l'ammonium. Rapportée à l'unité de masse de nodosités, elle est d'environ 25 μmoles C2H2/h/g MF quel que soit le traitement. Après la coupe, elle diminue considérablement puis revient à la normale en 2 semaines. La teneur en saccharose des nodosités de plantes 2 mM N03 ̅ et (1,65 mM N03 ̅ + 0,35 mM NH4+) est 2 fois plus faible un jour après la coupe qu'un jour avant. Les acides aminés de la sève xylémique sont 3 à 5 fois plus abondants chez les plantes N2 que lorsqu'il y a du nitrate ou du nitrate et de l'ammonium dans les solutions nutritives. Après une charge en 14CO2 (5 s) suivie d'une chasse de 55 s, la radioactivité totale incorporée est semblable dans les feuilles quel que soit le traitement. La radioactivité incorporée dans 1 'amidon est plus élevée chez les feuilles N2 que chez celles des plantes ayant du nitrate ou du nitrate et de 1 'ammonium dans leurs solutions nutritives

Download or read book Eighth International Congress of Applied Chemistry Washington and New York September 4 to 13 1912 written by and published by . This book was released on 1912 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Canadian Journal of Botany written by and published by . This book was released on 2002 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Catalogue of Scientific Papers written by Royal Society (Great Britain) and published by . This book was released on 1914 with total page 1066 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Original Communications written by and published by . This book was released on 1919 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrates agriculture eau written by R. Calvet and published by Editions Quae. This book was released on 1990 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: The contributions of this symposium on the relation agriculture-nitrogen-water deal with the economical aspects (cost evaluation and cost repartition), the quantitative approach of the nitrogen biochemical cycle, farming systems and nitrogen manegement, and land utilization, nitrogen management and water quality

Download or read book Catalogue of Scientific Papers 1800 1900 ser 4 1884 1900 written by Royal Society (Great Britain) and published by . This book was released on 1914 with total page 1066 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Methods of Studying Root Systems written by W. Böhm and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Root research under natural field conditions is still a step-child of science. The reason for this is primarily methodological. The known methods are tedious, time consuming, and the accuracy of their results is often not very great. Many research workers have been discouraged by doing such root studies. The need for more information on the development and distribution of plant roots in different soils under various ecological conditions is, however, obvious in many ecological disciplines. Especially the applied botanical sciences such as agriculture, horticulture, and forestry are interested in obtaining more data on plant roots in the soil. This book will give a survey of existing methods in ecological root research. Primarily field methods are presented; techniques for pot experiments are described only so far as they are important for solving ecological problems. Laboratory methods for studying root physiology are not covered in this book. Scientific publications on roots are scattered in many different journals published all over the world. By working through the international root literature I found that about ten thousand papers on root ecology have been published at the present. This is not very much compared with the immense literature on the aboveground parts of the plants, but is, however, too much to cite in this book.

Download or read book Plant Root Growth written by D. Atkinson and published by Blackwell Science. This book was released on 1991 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wachstum, Wurzel, Kanton Luzern.

Download or read book Special Publication of the British Ecological Society written by and published by . This book was released on 1982 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrogen Cycling in Coastal Marine Environments written by T. Henry Blackburn and published by . This book was released on 1988-03-21 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen discharge to the coastal environment has been increasing, posing the threat of accelerated eutrofication. Considerable research has been conducted in recent years to examine the impact of the nitrogen loading in coastal ecosystems. Based on proceedings from a SCOPE symposium held at the University of Aarhus in July of 1985, this volume covers a variety of up-to-date developments in research on nitrogen cycling in coastal marine environments. Topics include the role of nitrogen in algal productivity, regeneration of nutrients in the water column and the sediments, and the flow of nitrogen in coastal ecosystems.

Download or read book Catalogue of Scientific Papers ser 4 1884 1900 written by Royal Society (Great Britain) and published by . This book was released on 1867 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Horticultural Abstracts written by and published by . This book was released on 1981 with total page 1580 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Plant Aging written by Roberto Rodríguez and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 425 pages. Available in PDF, EPUB and Kindle. Book excerpt: For many, the terms aging, maturation and senescence are synonymous and used interchangeably, but they should not be. Whereas senescence represents an endogenously controlled degenerative programme leading to plant or organ death, genetiC aging encompasses a wide array of passive degenerative genetiC processes driven primarily by exogenous factors (Leopold, 1975). Aging is therefore considered a consequence of genetiC lesions that accumulate over time, but by themselves do not necessarily cause death. These lesions are probably made more severe by the increase in size and complexity in trees and their attendant physiology. Thus while the withering of flower petals following pollination can be considered senescence, the loss of viability of stored seeds more clearly represents aging (Norden, 1988). The very recent book "Senescence and Aging in Plants" does not discuss trees, the most dominant group of plants on the earth. Yet both angiospermic and gymnospermic trees also undergo the above phenomena but less is known about them. Do woody plants senesce or do they just age? What is phase change? Is this synonymous with maturation? While it is now becoming recognized that there is no programmed senescence in trees, senescence of their parts, even in gymnosperms (e. g. , needles of temperate conifers las t an average of 3. 5 years), is common; but aging is a readily acknowledged phenomenon. In theory, at least, in the absence of any programmed senescence trees should -live forever, but in practice they do not.