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Titolo:
Rapid effects of nitrogen form on leaf morphogenesis in tobacco
Autore:
Walch-Liu, P; Neumann, G; Bangerth, F; Engels, C;
Indirizzi:
Univ Hohenheim, Inst Pflanzenernahrung, D-70593 Stuttgart, Germany Univ Hohenheim Stuttgart Germany D-70593 ung, D-70593 Stuttgart, Germany Univ Hohenheim, Inst Obst Gemuse & Weinbau, D-70593 Stuttgart, Germany Univ Hohenheim Stuttgart Germany D-70593 bau, D-70593 Stuttgart, Germany Univ Bayreuth, Fachgrp Geowissensch, Abt Agrarokol, D-95440 Bayreuth, Germany Univ Bayreuth Bayreuth Germany D-95440 arokol, D-95440 Bayreuth, Germany
Titolo Testata:
JOURNAL OF EXPERIMENTAL BOTANY
fascicolo: 343, volume: 51, anno: 2000,
pagine: 227 - 237
SICI:
0022-0957(200002)51:343<227:REONFO>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
BETA-VULGARIS L; HIGHER-PLANTS; AMMONIUM NUTRITION; ABSCISIC-ACID; XYLEM SAP; CYTOKININ; NITRATE; GROWTH; METABOLISM; ROOTS;
Keywords:
ammonium; nitrate; leaf growth; cytokinin;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
64
Recensione:
Indirizzi per estratti:
Indirizzo: Walch-Liu, P Univ Hohenheim, Inst Pflanzenernahrung, D-70593 Stuttgart, Germany Univ Hohenheim Stuttgart Germany D-70593 Stuttgart, Germany
Citazione:
P. Walch-Liu et al., "Rapid effects of nitrogen form on leaf morphogenesis in tobacco", J EXP BOT, 51(343), 2000, pp. 227-237

Abstract

Ammonium (NH4+) instead of nitrate (NO3-) as the nitrogen (N) source for tobacco (Nicotiana tabacum L.) cultivated in a pH-buffered nutrient solutionresulted in decreased shoot and root biomass, Reduction of shoot fresh weight was mainly related to inhibition of leaf growth, which was already detectable after short-term NH4+ treatments of 24 h, and even at a moderate concentration level of 2 mM, Microscopic analysis of the epidermis of fully expanded leaves revealed a decrease in cell number (50%) and in cell size (30%) indicating that both cell division and cell elongation were affected by NH4+ application. Changes in various physiological parameters known to be associated with NH4+-induced growth depression were examined both in long-term and short-term experiments: the concentrations of total N, soluble sugars and starch as well as the osmotic potential, the apparent hydraulic conductivity and the rate of water uptake were not reduced by NH4+ treatments (duration 1-12 d), suggesting that leaf growth was neither limited by the availability of N and carbohydrates, nor by a lack of osmotica or water supply. Although the concentration of K+ in leaf press sap declined in expanding leaves by approximately 15% in response to NH4+ nutrition, limitation of mineral nutrients seems to be unlikely in view of the fast response of leaf growth at 24 h after the start of the NH4+ treatment. No inhibitory effects were observed when NH4+ and NO3- were applied simultaneously (each 1 mM) resulting in a NO3-/NH4+ net uptake ratio of 6 : 4. These findings suggest that the rapid inhibition of leaf growth was not primarily related to NH4+ toxicity, but to the lack of NO3--supply, Growth inhibition of plants fed solely with NH4+ was associated with a 60% reduction of the zeatine + zeatine riboside (Z + ZR) cytokinin fraction in the xylem sap after 24 h, Furthermore Z + ZR levels declined to almost zero within the next 4 d after start ofthe NH4+ treatment. In contrast, the concentrations of the putative Z + ZRprecursors isopentenyl-adenine and isopentenyl-adenosine (i-Ade + i-Ado) were not affected by NH4+ application. Since cytokinins are involved in the regulation of both cell division and cell elongation, it seems likely that the presence of NO3- is required to maintain biosynthesis and/or root to shoot transfer of cytokinins at a level that is sufficient to mediate normal leaf morphogenesis.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/09/20 alle ore 06:05:19