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Orkoien, Spain

Billard V.,University of Caen Lower Normandy | Billard V.,French National Institute for Agricultural Research | Maillard A.,University of Caen Lower Normandy | Maillard A.,French National Institute for Agricultural Research | And 9 more authors.
Plant Physiology and Biochemistry

In order to cope with variable mineral nutrient availability, higher plants have developed numerous strategies including the remobilization of nutrients from source to sink tissues. However, such processes remain relatively unknown for magnesium (Mg), which is the third most important cation in plant tissues. Using Mg depletion of Brassica napus, we have demonstrated that Mg is remobilized from old leaves to young shoot tissues. Moreover, this study showed that Mg depletion induces modification of nutrient uptake, especially Zn and Mn. Finally, comparative proteomic analysis of old leaves (source of Mg) revealed amongst other results that some proteins requiring Mg for their functionality (isocitrate dehydrogenase for example) were up-regulated. Moreover, down-regulation of proteases suggested that mobilization of Mg from old leaves was not associated with senescence. © 2016 Elsevier Masson SAS Source

Arkoun M.,University of Caen Lower Normandy | Arkoun M.,French National Institute for Agricultural Research | Sarda X.,University of Caen Lower Normandy | Sarda X.,French National Institute for Agricultural Research | And 10 more authors.
Journal of Experimental Botany

N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, 15N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of 15N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study. © [2012] The Author. Source

Billard V.,University of Caen Lower Normandy | Billard V.,French National Institute for Agricultural Research | Maillard A.,University of Caen Lower Normandy | Maillard A.,French National Institute for Agricultural Research | And 6 more authors.
Plant Physiology and Biochemistry

The importance of zinc (Zn) has been of little concern in human nutrition despite a strong decrease of this element in crops since the rise of high yielding varieties. For better food quality, Zn biofortification can be used, but will be optimal only if mechanisms governing Zn management are better known. Using Zn deficiency, we are able to demonstrate that Zn is not remobilized in Brassica napus ( B. napus). Thus, remobilization processes should not be targeted by biofortification strategies. This study also complemented previous work by investigating leaf responses to Zn deficiency, especially from proteomic and ionomic points of view, showing for example, an increase in Manganese (Mn) content and of the Mn-dependent protein, Oxygen Evolving Enhancer. © 2014 Elsevier Masson SAS. Source

Sorin E.,University of Caen Lower Normandy | Sorin E.,French National Institute for Agricultural Research | Etienne P.,University of Caen Lower Normandy | Etienne P.,French National Institute for Agricultural Research | And 6 more authors.
Journal of Experimental Botany

Identifcation of early sulphur (S) defciency indicators is important for species such as Brassica napus, an S-demanding crop in which yield and the nutritional quality of seeds are negatively affected by S defciency. Because S is mostly stored as SO4 2- in leaf cell vacuoles and can be mobilized during S defciency, this study investigated the impact of S deprivation on leaf osmotic potential in order to identify compensation processes. Plants were exposed for 28 days to S or to chlorine deprivation in order to differentiate osmotic and metabolic responses. While chlorine deprivation had no signifcant effects on growth, osmotic potential and nitrogen metabolism, Brassica napus revealed two response periods to S deprivation. The frst one occurred during the frst 13 days during which plant growth was maintained as a result of vacuolar SO4 2- mobilization. In the meantime, leaf osmotic potential of S-deprived plants remained similar to control plants despite a reduction in the SO4 2- osmotic contribution, which was fully compensated by an increase in NO3 -, PO4 3- and Cl- accumulation. The second response occurred after 13 days of S deprivation with a signifcant reduction in growth, leaf osmotic potential, NO3 - uptake and NO3 - reductase activity, whereas amino acids and NO3 - were accumulated. This kinetic analysis of S deprivation suggested that a ([Cl-]+[NO3 -]+[PO4 3-]):[SO4 2-] ratio could provide a relevant indicator of S defciency, modifed nearly as early as the over-expression of genes encoding SO4 2- tonoplastic or plasmalemmal transporters, with the added advantage that it can be easily quantifed under feld conditions. © 2015 The Author. Published by Oxford University Press on behalf of the Society for Experimental Biology. Source

Maillard A.,University of Caen Lower Normandy | Maillard A.,French National Institute for Agricultural Research | Diquelou S.,University of Caen Lower Normandy | Diquelou S.,French National Institute for Agricultural Research | And 9 more authors.
Frontiers in Plant Science

Higher plants have to cope with fluctuating mineral resource availability. However, strategies such as stimulation of root growth, increased transporter activities, and nutrient storage and remobilization have been mostly studied for only a few macronutrients. Leaves of cultivated crops (Zea mays, Brassica napus, Pisum sativum, Triticum aestivum, Hordeum vulgare) and tree species (Quercus robur, Populus nigra, Alnus glutinosa) grown under field conditions were harvested regularly during their life span and analyzed to evaluate the net mobilization of 13 nutrients during leaf senescence. While N was remobilized in all plant species with different efficiencies ranging from 40% (maize) to 90% (wheat), other macronutrients (K–P–S–Mg) were mobilized in most species. Ca and Mn, usually considered as having low phloem mobility were remobilized from leaves in wheat and barley. Leaf content of Cu–Mo–Ni–B–Fe–Zn decreased in some species, as a result of remobilization. Overall, wheat, barley and oak appeared to be the most efficient at remobilization while poplar and maize were the least efficient. Further experiments were performed with rapeseed plants subjected to individual nutrient deficiencies. Compared to field conditions, remobilization from leaves was similar (N–S–Cu) or increased by nutrient deficiency (K–P–Mg) while nutrient deficiency had no effect on Mo–Zn–B–Ca–Mn, which seemed to be non-mobile during leaf senescence under field conditions. However, Ca and Mn were largely mobilized from roots (-97 and -86% of their initial root contents, respectively) to shoots. Differences in remobilization between species and between nutrients are then discussed in relation to a range of putative mechanisms. © 2015 Maillard, Diquélou, Billard, Laîné, Garnica, Prudent, Garcia-Mina, Yvin and Ourry. Source

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