Modelling of Nitrogen Allocation and Partitioning Within Lucerne (\u3cem\u3eMedicago Sativa\u3c/em\u3e) Shoot Tissues During Recovery from Defoliation: An Approach to Estimate Forage Production and Nitrogen Composition

Lucerne has been grown over centuries for forage. Its forage production is strongly correlated to the initial taproot and stubble N reserves (Avice et al., 1996; Meuriot et al., 2004). However, the influence of cutting management on the level of N storage and the contribution of these N reserves to forage production still remain unclear and need to be studied at the whole plant level. For this purpose, a deterministic model of N allocation within the different organs and partitioning within different biochemical N pools was developed for lucerne with high and low initial N status and cutting heights of 6 or 15 cm

Retail Market Prices of Fonio Reveal The Demand For Quality Characteristics in Bamako, Mali

African consumers' expectations concerning the quality of food products are great. In spite of constrained budgets, we showed that market retail prices revealed quality preferences of the consumers and not just production costs. In very poor countries like Mali, food innovation is limited by the very low purchasing power of the population. However, technological food product or process innovations are possible and sometimes valuable. Demand driven innovation may lead to open new markets, opportunities for small and medium scale enterprises and to improve consumers' welfare. Based on this assumption, technical research was done to provide new food products. In this paper, we used both sensory tests and a hedonic price approach, to estimate the consumers' demand for different characteristics of fonio, a West African cereal, and showed that poor consumers have quality requirements and pay for them. We showed that the shadow price or hedonic price paid for quality characteristics is small but significant. A comparison between sensory tests and a market study showed a convergence between what people say they prefer and what they really pay for. Results were consistent and showed directions for technological improvement of the product and its production process. The partial least square method was used to estimate hedonic prices of the different modalities of fonio quality traits. This method was interesting since it solved the ordinary least square method's colinearity problems. ...French Abstract : Les attentes des consommateurs africains concernant la qualité de l'alimentation sont importantes malgré des budgets très contraints. Nous montrons ici que les prix de marchés révèlent des préférences qualitatives et non seulement des coûts de production. Dans des pays très pauvres comme le Mali, l'innovation technologique est limitée par le très faible pouvoir d'achat de la population. Cependant les innovations technologiques sont possibles et parfois payantes. L'innovation en réponse à une demande peut permettre d'ouvrir de nouveaux marchés, de donner des opportunités aux petites et moyennes entreprises et d'améliorer le bien-être des consommateurs. Sur la base de cette hypothèse, la recherche technologique s'applique à fournir de nouveaux produits. Dans cet article, en utilisant à la fois des tests de dégustation et une analyse des prix hédoniques, nous estimons la demande des consommateurs pour différentes caractéristiques du fonio, une céréale d'Afrique de l'Ouest. Nous montrons que des consommateurs pauvres ont des exigences de qualité et paient de fait pour les satisfaire. Nous montrons que les prix hédoniques ou shadow prices payés pour les caractéristiques qualitatives sont faibles mais significatifs. La comparaison des tests sensoriels et de l'étude de marché montre une convergence entre ce que les gens disent et ce pour quoi ils paient réellement. Les résultats sont cohérents et montrent des directions pour l'amélioration technologique des produits et des procédés de transformation. La méthode des moindres carrés ordinaires a été utilisée pour l'estimation des prix hédoniques des différentes modalités des attributs de qualité du fonio. Cette méthode est intéressante car elle résout les problèmes de colinéarité.FONIO; CEREAL; QUALITY; HEDONIC PRICES; PLS METHOD; EMPIRICAL INVESTIGATION

Improvement of Lucerne Cutting Management: The Relative Impact of Initial Organic Reserves, Cutting Height and Residual Leaf Area on Forage Yield

Less lucerne (Medicago sativa L.) is now grown because of difficulties arising from 2 interacting characteristics: productivity and stand persistence. Optimisation of these two parameters depends highly of the cutting management (cutting height and/or frequency) and of the taproot N reserves. For example, Avice et al. (1997) showed that lucerne shoot regrowth is relates closely to taproot soluble protein concentrations (especially vegetative storage protein: VSP). However, it is not known how stubble C-N reserves and/or residual leaf area (both depending of the cutting management) influence the contribution of taproot reserve-derived C-N supply to regrowing lucerne shoots after defoliation. This study aimed to estimate the role of stubble C/N reserves or residual leaf area (RLA) on the contribution of taproot N reserves to shoot regrowth of lucerne after cutting

Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability

The impact of sulphur limitation on the remobilization of endogenous S compounds during the rosette stage of oilseed rape, and the interactions with N availability on these processes, were examined using a long-term 34SO42− labelling method combined with a study of leaf senescence progression (using SAG12/Cab as a molecular indicator) and gene expression of the transporters, BnSultr4;1 and BnSultr4;2, involved in vacuolar sulphate efflux. After 51 d on hydroponic culture at 0.3 mM 34SO42− (1 atom% excess), the labelling was stopped and plants were subject for 28 d to High S-High N (HS-HN, control), Low S-High N (LS-HN) or Low S-Low N (LS-LN) conditions. Compared with the control, LS-HN plants showed delayed leaf senescence and, whilst the shoot growth and the foliar soluble protein amounts were not affected, S, 34S, and SO42− amounts in the old leaves declined rapidly and were associated with the up-regulation of BnSultr4;1. In LS-LN plants, shoot growth was reduced, leaf senescence was accelerated, and the rapid S mobilization in old leaves was accompanied by decreased 34S and SO42−, higher protein mobilization, and up-regulation of BnSultr4;2, but without any change of expression of BnSultr4;1. The data suggest that to sustain the S demand for growth under S restriction (i) vacuolar SO42− is specifically remobilized in LS-HN conditions without any acceleration of leaf senescence, (ii) SO42− mobilization is related to an up-regulation of BnSultr4;1 and/or BnSultr4;2 expression, and (iii) the relationship between sulphate mobilization and up-regulation of expression of BnSultr4 genes is specifically dependent on the N availability

Effect of mineral sulphur availability on nitrogen and sulphur uptake and remobilization during the vegetative growth of Brassica napus L.

Because it has a high demand for sulphur (S), oilseed rape is particularly sensitive to S limitation. However, the physiological effects of S limitation remain unclear, especially during the rosette stage. For this reason a study was conducted to determine the effects of mineral S limitation on nitrogen (N) and S uptake and remobilization during vegetative growth of oilseed rape at both the whole-plant and leaf rank level for plants grown during 35 d with 300 μM 34SO42– (control plants; +S) or with 15 μM 34SO42– (S-limited plants; –S). The results highlight that S-limited plants showed no significant differences either in whole-plant and leaf biomas or in N uptake, when compared with control plants. However, total S and 34S (i.e. deriving from S uptake) contents were greatly reduced for the whole plant and leaf after 35 d, and a greater redistribution of endogenous S from leaves to the benefit of roots was observed. The relative expression of tonoplast and plasmalemma sulphate transporters was also strongly induced in the roots. In conclusion, although S-limited plants had 20 times less mineral S than control plants, their development remained surprisingly unchanged. During S limitation, oilseed rape is able to recycle endogenous S compounds (mostly sulphate) from leaves to roots. However, this physiological adaptation may be effective only over a short time scale (i.e. vegetative growth)