RESUMO - Foram determinados o consumo de alimento e água por ovinos mantidos em câmara climática com temperatura ambiente de 22 a 25°C, empregando-se dietas com quatro níveis de energia metabolizável: nível normal, para ovinos de 30 kg, em engorda, 10% acima do nível normal e 10 e 20% abaixo do nível normal. Os resultados levaram às seguintes conclusões: 1. Os consumos de matéria seca, mat6ria seca digestível e energia digestível foram maiores na temperatura de 22 a 25 0C; 2. Os níveis de energia metabolizável das rações não tiveram influência sobre os consumos de mat6ria seca, mat6ria seca digestível, energia e proteína digestíveis; e 3. O consumo de água foi diretamente relacionado com a temperatura ambiente. ABSTRACT - Climatic chamber (22 - 25 0C and 32 - 35°C) was used to determine water and feed with four metabolizable energy leveis diets: normal levei 10% above the normal, and 10 and 20% below the normal levei for 30 kg liveweight ovines. The conclusions were: 1. Dry matter, digestible dry matter and digestible energy intake was higher at 22 - 25°C; 1 Energy leveis did not affect dry matter, digestible dry matter, digestible energy and digestible protein intake; and 3. Water consumption was directly associated to the environmental temperature.

National audience | Three irrigation schedules were tested on young peach trees Prunus persica (L) Batsch grown in pots (fig 1) under greenhouse conditions: - "micromorphometric irrigation", watering the trees according to maximum amplitude of daily stem contractions (fig 5), - "daily irrigation", maintaining the trees in constantly humid substrata and irrigating in compensation for transpiration loss, - "dry", watering the trees only when they closed their stomata. Both tree transpiration and leaf photosynthesis depend on the levels of water alimentation: transpiration reduction (fig 2) takes place as soon as the substrata dry out and net photosynthesis (table I) appears to be improved in the trees irrigated by the micromorphometric method under the conditions of low and medium light intensity, but limited in the trees subjected to "dry" treatment with a strong light intensity as compared with that observed in the trees which were irrigated daily. However, there are no significant differences in the water status and the stomatal resistance between the trees subjected to "daily irrigation" treatment and those on the "micromorphometry" schedule (figs 2, 3). The leaf water potential in the trees under the "dry" treatment is lower and their stomatal resistances are higher (figs 2, 3) than in trees on the daily irrigation schedule. Furthermore, the changes in the leaf water potential, the stomatal resistance and the daily maximal stem contraction (figs 6, 7) are examined according to substratum moisture and the relations between these different physiological parameters are studied (table II and fig 8). | Le comportement de certains processus physiologiques est étudié sur de jeunes pêchers (Prunus persica (L) Batsch), en pots sous serre, soumis à des régimes différents d’alimentation hydrique : - un arrosage conduit en fonction de l’amplitude maximum de contraction diurne de la tige (micromorphométrie); - un arrosage quotidien compensant la transpiration; - une alimentation en eau réduite : traitement arrosé seulement lorsque les arbres manifestent une fermeture stomatique (lot «sec»). La transpiration des arbres et la photosynthèse nette des feuilles sont fortement liées aux conditions d’alimentation hydrique : une réduction de la transpiration se met en place dès que le milieu se dessèche; la photosynthèse nette des arbres en pilotage micromorphométrique se maintient au même niveau que celle des arbres soumis au traitement «arrosage quotidien»; on observe même une tendance à paraître plus forte en condition de rayonnement solaire faible ou moyennement fort. Il n’y a pas de différence significative pour le potentiel hydrique et la résistance stomatique entre les arbres du traitement «arrosage quotidien» et ceux du pilotage micromorphométrique. Une limitation de la photosynthèse apparaît en condition de rayonnement fort sur les arbres du lot «sec» par rapport à celle des arbres arrosés tous les jours; le potentiel hydrique des arbres du traitement «sec» est plus bas et la résistance stomatique plus élevée. Par ailleurs, les évolutions, du potentiel hydrique foliaire, de la résistance stomatique et de l’amplitude maximum de contraction diurne de la tige sont examinées en fonction de l’état hydrique du milieu. Les liaisons entre ces différents paramètres physiologiques sont analysées.

National audience | Three irrigation schedules were tested on young peach trees (Prunus persica L Batsch) grown in pots under greenhouse conditions : - micromorphometric irrigation, watering the trees according to their daily stem contractions; - daily irrigation, maintaining the trees in the constantly humid substrata which compensated for transpiration losses; - dry; watering the trees only when the stomata were closed. The trees watered according to the micromorphometric method (fig 1) consumed less water compared with those under daily irrigation (table I). However, there was no difference in tree development and fruit growth between the 2 previous treatments (figs 2, 3, 4). There was no difference in the final mean area of 1 leaf between the 3 treatments (table II), although the roots of the trees under the micromorphometry treatment developed better (fig 5, table III). The dry treatment, on the one hand, strongly limited tree transpiration and on the other hand, reduced shoot elongation, stem diameter expansion and fruit size (figs 2, 3, 4). Moreover, the death of certain radicles occurred and the resumption of shoot growth was observed in trees under this treatment. The growth sensibility of different organs of peach trees to water stress and the irrigation scheduling based on the micromorphometric method are discussed (fig 6). | Le comportement de pêchers (Prunus persica (L) Batsch) a été étudié sur des jeunes arbres en pots, sous serre, soumis à des régimes différents d’alimentation hydrique : - arrosage conduit en fonction de l’amplitude maximale de contraction diurne de la tige (micromorphométrie); - arrosage quotidien compensant la transpiration; - alimentation en eau réduite (arrosage seulement lorsque les arbres manifestent une fermeture stomatique : lot sec). Les arbres arrosés par la méthode micromorphométrique ne se différencient pas de ceux dont on compense quotidiennement la transpiration, pour la croissance des parties végétatives et des fruits, mais ils consomment 20% d’eau en moins. Les racines des arbres en pilotage micromorphométrique s’étendent en outre davantage que celles des arbres arrosés quotidiennement. Par rapport aux 2 autres traitements, le traitement sec réduit fortement la transpiration des arbres, la croissance des pousses de l’année, la croissance secondaire de la tige et la taille des fruits. Il semble provoquer une réduction du nombre de radicelles et dans les parties aériennes, une reprise de la croissance de certaines pousses. La discussion porte sur la sensibilité de la croissance à la contrainte hydrique selon le type d’organe et sur le principe de la conduite micromorphométrique de l’irrigation.