Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-28T00:38:15.224Z Has data issue: false hasContentIssue false

Foliar application of nitrate or ammonium as sole nitrogen supply in Ricinus communis. I. Carbon and nitrogen uptake and inflows

Published online by Cambridge University Press:  01 April 1998

ANDREAS D. PEUKE
Affiliation:
Julius-von-Sachs-Institut für Biowissenschaften der Universität Würzburg, Lehrstuhl Botanik I, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
W. DIETER JESCHKE
Affiliation:
Julius-von-Sachs-Institut für Biowissenschaften der Universität Würzburg, Lehrstuhl Botanik I, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
KARL-JOSEF DIETZ
Affiliation:
Julius-von-Sachs-Institut für Biowissenschaften der Universität Würzburg, Lehrstuhl Botanik I, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
LUKAS SCHREIBER
Affiliation:
Julius-von-Sachs-Institut für Biowissenschaften der Universität Würzburg, Lehrstuhl Botanik II, Experimentelle Ökologie und Vegetationskunde, Julius-von-Sachs-Platz 3, D-97082 Würzburg, Germany
WOLFRAM HARTUNG
Affiliation:
Julius-von-Sachs-Institut für Biowissenschaften der Universität Würzburg, Lehrstuhl Botanik I, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
Get access

Abstract

Following a precultivation with pedospheric nitrogen nutrition, nitrate or ammonium solutions were supplied to the shoots of Ricinus plants by spraying (during the experimental period) resulting in an increase of biotic/organic and abiotic/inorganic particles on the surface, which significantly increased wetting of the leaf surfaces. The distribution of particles on the surface of sprayed leaves, in particular crystals around and in stomata, indicated the possible entry of nutrients via thin water films through the stomatal pores in addition to diffusion through the cuticle. Ammonium was taken up more readily than nitrate by the foliage, but both at relatively low rates which caused N limitation. Interestingly, the inorganic N, both in the form of nitrate and even ammonium, was entirely assimilated in the shoots; phloem transport of inorganic N to the root was negligible. The flows of malate, and the acidification of the apoplastic washing solution of leaves in ammonium-sprayed plants pointed to the role of metabolism of malate and excretion of protons in maintaining pH during ammonium assimilation in the shoot. Ammonium-sprayed plants incorporated the N in the same amounts in shoots and roots, only 38% of the shoot-borne N being recycled in the xylem. In nitrate-sprayed plants the root was not only favoured in N partitioning, but even a net export of previously incorporated N from the shoots occurred which reflected the N limitation. The N limitation also affected carbon metabolism, in particular the flows of C, incorporation in the shoot and photosynthesis, which were decreased when compared with data from recent experiments with pedospheric well fed Ricinus. However, there was little difference in C flows between nitrate and ammonium-sprayed plants with respect to respiration, C partitioning and, most interestingly, in relative stimulation of root growth. The loss of C from dark respiration of the shoots was high on a f. wt basis as well as in relative terms, owing to exclusive N assimilation in the shoot. In general the plants invested untargeted increases in root growth as a result of N limitation irrespective of the imposed artificial treatment which made the shoot the site of mineral N uptake.

Type
Research Article
Copyright
© Trustees of the New Phytologist 1998

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)