Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 154 (2011)
The role of phytohormons in the onset and development of leaf
senescence under nitrogen starvation in winter oilseed rape
(Brassica napus L.) genotypes differing in nitrogen efficiency
Fabian Köslin-Findeklee 1 , Sebastian Parra-Londono 1 , Gunda Schulte auf’m Erley 1 ,
Thomas Roitsch 2 and Walter J. Horst 1
1 Institute of Plant Nutrition, Gottfried Wilhelm Leibniz University Hannover; 2 Institute of Plant Sciences,
Karl-Franzens-University, Graz, Österreich. E-Mail: koeslin-findeklee@pflern.uni-hannover.de
Introduction
Winter oilseed rape is the most important oil crop in European agriculture, but one
with the highest nitrogen (N) balance surpluses. This may negatively impact the
environment. N starvation induces leaf senescence. Phytohormons are involved in
the onset and development of leaf senescence. Cytokinins and auxins are
senescence-delaying; salicylic (SA) and jasmonic acid (JA) are senescenceenhancing
(Lim et al. 2007). We hypothesized that delayed leaf senescence is
beneficial to yield formation because of maintained photosynthesis into the
reproductive growth stage (Wiesler et al. 2001). The aim of the study was to clarify if
genotypic differences in leaf senescence under N deficiency correspond to the effect
of certain phytohormons.
Material and Methods
A time-course nutrient solution experiment was performed with two pairs of
genotypes (NPZ-1: N-efficient & NPZ-2: N-inefficient / Apex: N-efficient & Capitol: Ninefficient)
which differ in leaf senescence (stay green) and yield formation under Nlimited
conditions. The plants were grown after a four weeks pre-culture for another
12 days under different N levels (0.1 mM N and 4.0 mM N).
Results and Discussion
SPAD and photosynthesis rate were suitable for detecting genotypic differences in
leaf senescence, but the photosynthesis rate was more sensitive. The expression
profiles of selected senescence associated genes (quantitative Real Time- PCR) in
senescing leaves also reflected genotypic differences in leaf senescence. Preliminary
evaluation of the results revealed that N deficiency sensitively induced the transport
of SA and JA transport from the roots to the shoots. Presently, an inventory of the
pattern of the concentrations of phytohormones including SA and JA in roots, leaves
and xylem exudates is in progress. To back up these results the expression of genes
related to the metabolism of phytohormones using qRT-PCR is being analysed.
References
Lim, P.O., Kim, H.J., Nam, H.G. 2007: Leaf senescence. Annual Review of Plant Biology. 58:115-36.
Wiesler, F., Behrens, T., Horst, W.J. 2001: Nitrogen efficiency of contrasting rape ideotypes. In: Horst,
W.J. et al. (eds.) Plant nutrition – Food security and sustainability of agro-ecosystems. Dordrecht,
Kluwer, 92:60-61.