HAL (Le Centre pour la Communication Scientifique Directe), 1984
Nous proposons une hypothèse pour rendre compte de faits connus : l'azote, l'eau, la température,... more Nous proposons une hypothèse pour rendre compte de faits connus : l'azote, l'eau, la température, les états de développement agissent beaucoup moins sur la photosynthèse que sur la croissance. Leur action sur cette dernière se présente toujours de la même manière, c'est-à-dire qu'elles modulent le comportement de la plante entre deux pôles : e forte croissance : le carbone est investi d'abord dans la croissance aérienne, au détriment des parties non photosynthétisantes. Il en résulte en principe une meilleure interception de la lumière, et le supplément de carbone capté permet ensuite une meilleure croissance de la plante entière. Mais parfois une croissance trop rapide entraîne un épuisement des réserves carbonées et la mort de la plante. e faible croissance : le carbone est dirigé surtout vers les réserves et/ou les racines. D'après notre hypothèse, la croissance ne serait pas déterminée par la photosynthèse. Il existerait un « programme » potentiel de croissance aérienne, lié aux états d'induction (« mémoire » de la plante). L'azote, l'eau, la température pourraient limiter la réalisation de ce potentiel. La croissance ainsi déterminée orienterait la destination du carbone par simple effet de « puits ».
Abstract Assessing the plant nitrogen (N) status is one of the major challenges for improving N f... more Abstract Assessing the plant nitrogen (N) status is one of the major challenges for improving N fertilization management and reducing its environmental footprint on forage-based agricultural systems. We re-analyzed a dataset of biomass (W) and plant N concentration (%N) of tall fescue (Festuca arundinacea Schreb.) using a Bayesian statistical model for estimating the coefficients of the critical N (%Nc) dilution curve (Nc = A1 W −A2) with two objectives in mind: i) to revise the reference %Nc dilution curve established for tall fescue by Lemaire and Salette (1984), and ii) to analyze how the determination of %Nc curves is affected by the structure of the dataset (number of sampling dates and N rates) along with the range of shoot %N and W achieved. Our analysis suggests that the original tall fescue %Nc curve of Lemaire and Salette (1984) was overestimated. A critical %N curve for tall fescue was obtained using the Bayesian method across 14 unique genotype × environment × management (G × E × M) conditions (Nc = 3.93 W -0.42). We show that the high uncertainty associated with the %Nc curve could be reduced by increasing the number of experiments. When a single dataset was used, 95 % credibility intervals (95 % CI) were [2.52, 5.66] for A1 and [0.06, 0.63] for A2. However, 95 % CI were reduced up to a 73 % when the critical N dilution curve was based on 14 studies. We also show that a minimum of five studies (+100 data points for our study) are needed to avoid large biases and uncertainty levels in coefficient estimations with the Bayesian method. However, these studies must be carefully designed. The reliability of critical %N curves is greatly reduced when they are estimated with datasets comprising only a few data under non-limiting N conditions or data covering only very low or high W values. Our results suggest that more reliable critical N dilution curves for species can be developed by grouping numerous datasets covering a broad range of G × E × M conditions.
In addition to morphological factors (height of the plant, proportion of stems), alfalfa quality ... more In addition to morphological factors (height of the plant, proportion of stems), alfalfa quality is related to several biochemical factors, especially the content and monomeric composition of the cell wall components. This work was aimed at studying internode development in relation to the chemical composition and fractionation of cell walls. Analyses were performed on the fourth apical internodes (elongating), the two following ones (onset of cambial activity), and bottom internodes (mature). Deposition of guaiacyl type lignin occurred in the pectin rich cell walls of apical internodes. The onset of cambial activity corresponded to cell wall accumulation of syringyl-guaiacyl lignin, xylans and/or glucuronoxylans, and cellulose. Such events were related to the thickening of secondary cell walls which proportion increased in mature internodes. Chemical fractionation of the cell walls allowed the release of a high content of water soluble pectins from apical internodes, whereas alkalis were more efficient in extracting heteroxylans from bottom internodes. A partial release of lignin from the cell walls also occurred during the extraction steps. Lignin solubilization was enhanced by the cleavage of labile-ether lignin structures and appeared closely related to the extent of internode differentiation along the stem. Data gained from chemical fractionations evidenced that lignin-xylan-pectic complexes accumulated progressively in secondary wall rich tissues.
... 1). One may note the similarity with eqn (2). The relative stability of the two coefficients ... more ... 1). One may note the similarity with eqn (2). The relative stability of the two coefficients indicates that the ... 488 Lemaire et al.Nitrogen Distribution Within a Lucerne Canopy ... This may explain the allometry coefficient of two-thirds obtained in many situations (Lemaire et al., 1985 ...
... Reference is made to the experiments on potatoes grown in Scotland by Millard and Marshall (1... more ... Reference is made to the experiments on potatoes grown in Scotland by Millard and Marshall (1986), to potatoes grown in the Netherlands by Neeteson et al. (1987), to winter wheat grown in Sweden by Siman (1974) and to tall fescue grown in central West France by Lemaire ...
ABSTRACT The effects of daily herbage allowance (DHA = herbage mass [HM] x daily offered area [DO... more ABSTRACT The effects of daily herbage allowance (DHA = herbage mass [HM] x daily offered area [DOA]) and cow characteristics upon herbage intake at grazing were assessed in two experiments. In experiment 1, two DHA (low and medium, 19 and 26 kg organic matter [OM]/cow/day) were compared in a continuous design using two groups of five cows. In experiment 2, three DHA (low, medium and high, 19, 29 and 46 kg OM/cow/day) were compared in a 3 x 3 latin square design using three groups of five cows. Mid-lactating cows (six first lactation per trial) were used. Fat-corrected milk at turnout (FCMt) ranged between 17 to 35 kg and live weight (LW) from 510 to 680 kg. Cows strip-grazed plots of vegetative Lolium perenne and did not receive concentrates. Herbage mass cut to ground level (HM) ranged from 3.5 to 7.1 t OM/ha. In experiment 1, herbage organic matter intake (HOMI) (13.5 vs 14.9 kg/day) and FCM yield (20.6 vs 22.0 kg/day) tended to increase from low to medium DHA but differences were not significant. In experiment 2, HOMI increased in a quadratic manner (13.8, 16.2 and 16.7 kg/day) and FCM increased linearly (P < 0.01) with DHA (20.4, 21.7 and 23.0 kg/day for low, medium and high DHA, respectively). In both experiments, HOMI was consistently lower in first lactation compared to adult cows and large between-cow variations within lactation were noted. From the pooled data, HOMI was related to DHA and cow characteristics: HOMI = 7.9 - 98 DHA(-1) + 0.264 FCMt + 0.0073 LW (n = 95, R(2) = 0.60, rsd = 1.77 kg). However, splitting DHA into its two components accounted for more of the variance in HOMI: HOMI = -20.4 - 115 DOA(-1) + 9.63 HM - 0.873 HM(2) + 0.266 FCMt + 0.0095 LW (R(2) = 0.70, rsd = 1.56 kg). These relationships showed that HOMI was affected by DHA but the original sward herbage mass/structure does have an independant effect in regulating intake. Moreover, voluntary intake increases with the potential of milk yield and this increase could account for the two-thirds of the supplementary energy requirements.
... AB15 8QH, UK F. Montossi, Instituto Nacional de Investigacion Agropecuaria (INIA), Estacion E... more ... AB15 8QH, UK F. Montossi, Instituto Nacional de Investigacion Agropecuaria (INIA), Estacion Experimental del None, Ruta 5, km ... Porto Alegre, Brazil CJ Nelson, Department of Agronomy, University of Missouri, Columbia, MO 65211, USA A. Oliveira Machado, Departamentato ...
... Samples of 0.1 g of dried and ground shoot biomass and leaf disks were mineralized using a mi... more ... Samples of 0.1 g of dried and ground shoot biomass and leaf disks were mineralized using a mixture of sul-furic and selenious acids (Isaac and Johnson, 1976), and N was quantified on a QuikChem 8000 Lachat autoanalyzer using the Lachat method 15-501-3 (Lachat ...
... la teneur en ADF et la teneur en azote de la luzerne (Medicago sativa L.) G. Lemaire J.-L. Du... more ... la teneur en ADF et la teneur en azote de la luzerne (Medicago sativa L.) G. Lemaire J.-L. Durand 1 M. Lila 2 1 INRA, station d'écophysiologie des plantes fourragères, 86 600 Lusignan; 2 INRA, station d'amélioration des plantes fourragères, 86 600 Lusignan, France ...
— The previous paper showed that autumn nitrogen supply affected the earliness of spring go... more — The previous paper showed that autumn nitrogen supply affected the earliness of spring gowth in tall fescue (cv. Clarine) at Lusignan, west central France. This paper deals with the dynamics of nitrogen uptake during winter.
— The dynamics of dry-matter accumulation and nitrogen uptake of sorghum and maize crops we... more — The dynamics of dry-matter accumulation and nitrogen uptake of sorghum and maize crops were compared over two successive years under dry and irrigated conditions. In non-limiting situations for growth, with irrigation and high nitrogen fertilization, maize growth was higher than that of sorghum because the leaf area index of maize developed earlier, leading to a larger quantity of intercepted radiation. The efficiency of transforming intercepted energy into aerial biomass varied little between the two species. In situations where nitrogen was limiting, the capacity of sorghum crops to take up nitrogen from the soil was always higher than that of maize. This feature was not linked to the greater planting density of the sorghum crop (50 cm between the rows) compared with the maize crop (75 cm), but seemed to be a characteristic of the species. A careful study of the evolution of the nitrogen nutrition level of the different crops throughout their growth showed that sorghum was capable of taking up much larger quantities of nitrogen from the soil than maize before its nitrogen nutrition became limiting. Drought reduced nitrogen availability in the soil for both crops. Maize was more sensitive to this restriction in nitrogen nutrition, and in addition to the direct effect of a water deficit on dry-matter accumulation in maize there was also this indirect effect of a nitrogen-nutrition deficit. All the results obtained in this series of experiments showed that the potential production of sorghum was lower than that of maize, but that its adaptation to limiting growth conditions, drought and limited nitrogen input should enable this species to grow in extensive cropping conditions. Moreover, the higher N uptake/water consumption of sorghum compared to maize indicates that the risk of nitrate leaching in the winter following a sorghum crop should be lower than after maize. nitrogen uptake capacity / nitrogen nutrition index / water-nitrogen interaction Résumé — Capacités de prélèvement d'azote de cultures de maïs et de sorgho dans différentes conditions d'alimentation hydrique. Durant 2 années successives, les dynamiques de croissance en matière sèche et de prélèvement d'azote de cultures de sorgho et de maïs ont été comparées en conditions sèches et irriguées. En situations non limitantes pour la croissance, irrigation et fertilisation élevée en azote, la croissance du maïs est supérieure à celle du sorgho du fait d'une mise en place plus précoce de l'indice foliaire de la culture conduisant à une plus grande quantité de rayonnement intercepté. Les efficiences de transformation de l'énergie interceptée en biomasse aérienne restent peu différentes entre les deux espèces. En situations d'apport limité en azote, les capacités de prélèvement de l'azote du sol par les cultures de sorgho ont toujours été supérieures à celles du maïs. Cette propriété n'est pas liée à la densité de plantation plus importante de la culture du sorgho (50 cm entre les rangs) par rapport à celle du maïs (75 cm), mais semble bien une caractéristique de l'espèce. La détermination de l'évolution du * Correspondence and reprints niveau de nutrition azotée des différentes cultures au cours de leur croissance a permis de montrer que le sorgho était capable d'extraire des quantités d'azote du sol bien supérieures à celles du maïs avant de voir sa nutrition azotée devenir limitante. La sécheresse diminue la disponibilité en azote du sol pour les deux cultures. Le maïs est plus sensible à cette restriction de nutrition azotée, et, à l'effet direct du déficit hydrique sur la croissance en matière sèche de cette espèce, s'ajoute un effet indirect de déficit de nutrition azotée. L'ensemble des résultats obtenus dans cette série d'expérimentations montre que la production potentielle du sorgho est plus faible que celle du maïs, mais que son adaptation à des conditions limitantes de croissance, sécheresse et apports limités d'azote doit permettre à cette espèce de se développer dans des conditions de culture extensive. De plus, le rapport plus élevé pour le sorgho que pour le maïs entre le prélèvement d'azote et la consommation d'eau indique que les risques de lessivage de nitrate doivent être réduits après une culture de sorgho en comparaison avec le maïs. capacité de prélèvement d'azote / index de nutrition azotée / interaction eau-azote
HAL (Le Centre pour la Communication Scientifique Directe), 1984
Nous proposons une hypothèse pour rendre compte de faits connus : l'azote, l'eau, la température,... more Nous proposons une hypothèse pour rendre compte de faits connus : l'azote, l'eau, la température, les états de développement agissent beaucoup moins sur la photosynthèse que sur la croissance. Leur action sur cette dernière se présente toujours de la même manière, c'est-à-dire qu'elles modulent le comportement de la plante entre deux pôles : e forte croissance : le carbone est investi d'abord dans la croissance aérienne, au détriment des parties non photosynthétisantes. Il en résulte en principe une meilleure interception de la lumière, et le supplément de carbone capté permet ensuite une meilleure croissance de la plante entière. Mais parfois une croissance trop rapide entraîne un épuisement des réserves carbonées et la mort de la plante. e faible croissance : le carbone est dirigé surtout vers les réserves et/ou les racines. D'après notre hypothèse, la croissance ne serait pas déterminée par la photosynthèse. Il existerait un « programme » potentiel de croissance aérienne, lié aux états d'induction (« mémoire » de la plante). L'azote, l'eau, la température pourraient limiter la réalisation de ce potentiel. La croissance ainsi déterminée orienterait la destination du carbone par simple effet de « puits ».
Abstract Assessing the plant nitrogen (N) status is one of the major challenges for improving N f... more Abstract Assessing the plant nitrogen (N) status is one of the major challenges for improving N fertilization management and reducing its environmental footprint on forage-based agricultural systems. We re-analyzed a dataset of biomass (W) and plant N concentration (%N) of tall fescue (Festuca arundinacea Schreb.) using a Bayesian statistical model for estimating the coefficients of the critical N (%Nc) dilution curve (Nc = A1 W −A2) with two objectives in mind: i) to revise the reference %Nc dilution curve established for tall fescue by Lemaire and Salette (1984), and ii) to analyze how the determination of %Nc curves is affected by the structure of the dataset (number of sampling dates and N rates) along with the range of shoot %N and W achieved. Our analysis suggests that the original tall fescue %Nc curve of Lemaire and Salette (1984) was overestimated. A critical %N curve for tall fescue was obtained using the Bayesian method across 14 unique genotype × environment × management (G × E × M) conditions (Nc = 3.93 W -0.42). We show that the high uncertainty associated with the %Nc curve could be reduced by increasing the number of experiments. When a single dataset was used, 95 % credibility intervals (95 % CI) were [2.52, 5.66] for A1 and [0.06, 0.63] for A2. However, 95 % CI were reduced up to a 73 % when the critical N dilution curve was based on 14 studies. We also show that a minimum of five studies (+100 data points for our study) are needed to avoid large biases and uncertainty levels in coefficient estimations with the Bayesian method. However, these studies must be carefully designed. The reliability of critical %N curves is greatly reduced when they are estimated with datasets comprising only a few data under non-limiting N conditions or data covering only very low or high W values. Our results suggest that more reliable critical N dilution curves for species can be developed by grouping numerous datasets covering a broad range of G × E × M conditions.
In addition to morphological factors (height of the plant, proportion of stems), alfalfa quality ... more In addition to morphological factors (height of the plant, proportion of stems), alfalfa quality is related to several biochemical factors, especially the content and monomeric composition of the cell wall components. This work was aimed at studying internode development in relation to the chemical composition and fractionation of cell walls. Analyses were performed on the fourth apical internodes (elongating), the two following ones (onset of cambial activity), and bottom internodes (mature). Deposition of guaiacyl type lignin occurred in the pectin rich cell walls of apical internodes. The onset of cambial activity corresponded to cell wall accumulation of syringyl-guaiacyl lignin, xylans and/or glucuronoxylans, and cellulose. Such events were related to the thickening of secondary cell walls which proportion increased in mature internodes. Chemical fractionation of the cell walls allowed the release of a high content of water soluble pectins from apical internodes, whereas alkalis were more efficient in extracting heteroxylans from bottom internodes. A partial release of lignin from the cell walls also occurred during the extraction steps. Lignin solubilization was enhanced by the cleavage of labile-ether lignin structures and appeared closely related to the extent of internode differentiation along the stem. Data gained from chemical fractionations evidenced that lignin-xylan-pectic complexes accumulated progressively in secondary wall rich tissues.
... 1). One may note the similarity with eqn (2). The relative stability of the two coefficients ... more ... 1). One may note the similarity with eqn (2). The relative stability of the two coefficients indicates that the ... 488 Lemaire et al.Nitrogen Distribution Within a Lucerne Canopy ... This may explain the allometry coefficient of two-thirds obtained in many situations (Lemaire et al., 1985 ...
... Reference is made to the experiments on potatoes grown in Scotland by Millard and Marshall (1... more ... Reference is made to the experiments on potatoes grown in Scotland by Millard and Marshall (1986), to potatoes grown in the Netherlands by Neeteson et al. (1987), to winter wheat grown in Sweden by Siman (1974) and to tall fescue grown in central West France by Lemaire ...
ABSTRACT The effects of daily herbage allowance (DHA = herbage mass [HM] x daily offered area [DO... more ABSTRACT The effects of daily herbage allowance (DHA = herbage mass [HM] x daily offered area [DOA]) and cow characteristics upon herbage intake at grazing were assessed in two experiments. In experiment 1, two DHA (low and medium, 19 and 26 kg organic matter [OM]/cow/day) were compared in a continuous design using two groups of five cows. In experiment 2, three DHA (low, medium and high, 19, 29 and 46 kg OM/cow/day) were compared in a 3 x 3 latin square design using three groups of five cows. Mid-lactating cows (six first lactation per trial) were used. Fat-corrected milk at turnout (FCMt) ranged between 17 to 35 kg and live weight (LW) from 510 to 680 kg. Cows strip-grazed plots of vegetative Lolium perenne and did not receive concentrates. Herbage mass cut to ground level (HM) ranged from 3.5 to 7.1 t OM/ha. In experiment 1, herbage organic matter intake (HOMI) (13.5 vs 14.9 kg/day) and FCM yield (20.6 vs 22.0 kg/day) tended to increase from low to medium DHA but differences were not significant. In experiment 2, HOMI increased in a quadratic manner (13.8, 16.2 and 16.7 kg/day) and FCM increased linearly (P < 0.01) with DHA (20.4, 21.7 and 23.0 kg/day for low, medium and high DHA, respectively). In both experiments, HOMI was consistently lower in first lactation compared to adult cows and large between-cow variations within lactation were noted. From the pooled data, HOMI was related to DHA and cow characteristics: HOMI = 7.9 - 98 DHA(-1) + 0.264 FCMt + 0.0073 LW (n = 95, R(2) = 0.60, rsd = 1.77 kg). However, splitting DHA into its two components accounted for more of the variance in HOMI: HOMI = -20.4 - 115 DOA(-1) + 9.63 HM - 0.873 HM(2) + 0.266 FCMt + 0.0095 LW (R(2) = 0.70, rsd = 1.56 kg). These relationships showed that HOMI was affected by DHA but the original sward herbage mass/structure does have an independant effect in regulating intake. Moreover, voluntary intake increases with the potential of milk yield and this increase could account for the two-thirds of the supplementary energy requirements.
... AB15 8QH, UK F. Montossi, Instituto Nacional de Investigacion Agropecuaria (INIA), Estacion E... more ... AB15 8QH, UK F. Montossi, Instituto Nacional de Investigacion Agropecuaria (INIA), Estacion Experimental del None, Ruta 5, km ... Porto Alegre, Brazil CJ Nelson, Department of Agronomy, University of Missouri, Columbia, MO 65211, USA A. Oliveira Machado, Departamentato ...
... Samples of 0.1 g of dried and ground shoot biomass and leaf disks were mineralized using a mi... more ... Samples of 0.1 g of dried and ground shoot biomass and leaf disks were mineralized using a mixture of sul-furic and selenious acids (Isaac and Johnson, 1976), and N was quantified on a QuikChem 8000 Lachat autoanalyzer using the Lachat method 15-501-3 (Lachat ...
... la teneur en ADF et la teneur en azote de la luzerne (Medicago sativa L.) G. Lemaire J.-L. Du... more ... la teneur en ADF et la teneur en azote de la luzerne (Medicago sativa L.) G. Lemaire J.-L. Durand 1 M. Lila 2 1 INRA, station d'écophysiologie des plantes fourragères, 86 600 Lusignan; 2 INRA, station d'amélioration des plantes fourragères, 86 600 Lusignan, France ...
— The previous paper showed that autumn nitrogen supply affected the earliness of spring go... more — The previous paper showed that autumn nitrogen supply affected the earliness of spring gowth in tall fescue (cv. Clarine) at Lusignan, west central France. This paper deals with the dynamics of nitrogen uptake during winter.
— The dynamics of dry-matter accumulation and nitrogen uptake of sorghum and maize crops we... more — The dynamics of dry-matter accumulation and nitrogen uptake of sorghum and maize crops were compared over two successive years under dry and irrigated conditions. In non-limiting situations for growth, with irrigation and high nitrogen fertilization, maize growth was higher than that of sorghum because the leaf area index of maize developed earlier, leading to a larger quantity of intercepted radiation. The efficiency of transforming intercepted energy into aerial biomass varied little between the two species. In situations where nitrogen was limiting, the capacity of sorghum crops to take up nitrogen from the soil was always higher than that of maize. This feature was not linked to the greater planting density of the sorghum crop (50 cm between the rows) compared with the maize crop (75 cm), but seemed to be a characteristic of the species. A careful study of the evolution of the nitrogen nutrition level of the different crops throughout their growth showed that sorghum was capable of taking up much larger quantities of nitrogen from the soil than maize before its nitrogen nutrition became limiting. Drought reduced nitrogen availability in the soil for both crops. Maize was more sensitive to this restriction in nitrogen nutrition, and in addition to the direct effect of a water deficit on dry-matter accumulation in maize there was also this indirect effect of a nitrogen-nutrition deficit. All the results obtained in this series of experiments showed that the potential production of sorghum was lower than that of maize, but that its adaptation to limiting growth conditions, drought and limited nitrogen input should enable this species to grow in extensive cropping conditions. Moreover, the higher N uptake/water consumption of sorghum compared to maize indicates that the risk of nitrate leaching in the winter following a sorghum crop should be lower than after maize. nitrogen uptake capacity / nitrogen nutrition index / water-nitrogen interaction Résumé — Capacités de prélèvement d'azote de cultures de maïs et de sorgho dans différentes conditions d'alimentation hydrique. Durant 2 années successives, les dynamiques de croissance en matière sèche et de prélèvement d'azote de cultures de sorgho et de maïs ont été comparées en conditions sèches et irriguées. En situations non limitantes pour la croissance, irrigation et fertilisation élevée en azote, la croissance du maïs est supérieure à celle du sorgho du fait d'une mise en place plus précoce de l'indice foliaire de la culture conduisant à une plus grande quantité de rayonnement intercepté. Les efficiences de transformation de l'énergie interceptée en biomasse aérienne restent peu différentes entre les deux espèces. En situations d'apport limité en azote, les capacités de prélèvement de l'azote du sol par les cultures de sorgho ont toujours été supérieures à celles du maïs. Cette propriété n'est pas liée à la densité de plantation plus importante de la culture du sorgho (50 cm entre les rangs) par rapport à celle du maïs (75 cm), mais semble bien une caractéristique de l'espèce. La détermination de l'évolution du * Correspondence and reprints niveau de nutrition azotée des différentes cultures au cours de leur croissance a permis de montrer que le sorgho était capable d'extraire des quantités d'azote du sol bien supérieures à celles du maïs avant de voir sa nutrition azotée devenir limitante. La sécheresse diminue la disponibilité en azote du sol pour les deux cultures. Le maïs est plus sensible à cette restriction de nutrition azotée, et, à l'effet direct du déficit hydrique sur la croissance en matière sèche de cette espèce, s'ajoute un effet indirect de déficit de nutrition azotée. L'ensemble des résultats obtenus dans cette série d'expérimentations montre que la production potentielle du sorgho est plus faible que celle du maïs, mais que son adaptation à des conditions limitantes de croissance, sécheresse et apports limités d'azote doit permettre à cette espèce de se développer dans des conditions de culture extensive. De plus, le rapport plus élevé pour le sorgho que pour le maïs entre le prélèvement d'azote et la consommation d'eau indique que les risques de lessivage de nitrate doivent être réduits après une culture de sorgho en comparaison avec le maïs. capacité de prélèvement d'azote / index de nutrition azotée / interaction eau-azote
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