SUMMARYFour-and five-year-old 'Merrill Sunda~ce' peach trees, protected from rainfall by polyethylene film covers, were fully irrigated using micro-sprinkler (irrigatio~scheduling based on a tensiometer technique), or subjected to water stress at different phenological stages of fruit growth. Water deficit imposed during the first phase of rapid growth significantly increased fruit size at harvest during two experimental years when compared with the control full-irrigation treatment, while smaller fruits were produced from trees receiving an imposed water deficit during the final accelerated fruit growth, or throughout the fruit development period. When water deficit was applied to the trees during the pit hardening phase and the first two phases of fruit development, fruit size was not affected. However, shoot extension growth and limb diameter increases were limited whenever water supply was restricted. After-effects on limb expansion growth and benefits of water stress on fruit growth were obvious during the post-stress period. Moreover, premature fruit drops after the June-drop were reduced for all the water stress treatments. The level of total soluble solids was higher in fruits from the trees subjected to water stress during the final rapid phase of fruit growth, and flower bud production was improved on trees given a restricted supply of water during the critical period of flower bud induction.

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F 84140 Montfavet RÉSUMÉ Les variétés d'aubergine méditerranéennes ont un indice et une densité stomatiques supérieurs à ceux des variétés extrême-orientales, aussi bien dans le cas de jeunes plantes de 5-6 feuilles élevées en serre, que dans celui des plantes adultes cultivées l'été au champ. Ce résultat ne varie pas quand le niveau d'éclairement naturel est diminué de 50 p. 100 par ombrage. Les fréquences stomatiques moyennes des variétés sont en relation positive avec les poids secs moyens de leur système racinaire. Ce résultat suggère que les mesures de fréquence stomatique pourraient devenir une méthode « non destructive » de mesure de la matière sèche des racines. Un travail futur examinera cette question plus précisément. Mots clés additionnels : Variétés, écotypes, indice stomatigue, densité stomatique, éclairement. SUMMARY Stomatal frequencies of eggplant (Solanum melongena L.) and relationships with root development. Mediterranean eggplant varieties (M) had higher stomatal index and stomatal density than far-eastern varieties (EO in text) both for young plants with 5-6 leaves grown in a greenhouse and for adult plants grown in the open under summer irrigation. This result was the same when the natural light level was 50 % reduced by shade. Stomatal frequency means of varieties were po.sitively related (see fig. 5) with their root dry weight means. The significance of this result lies in the suggestion that stomatal parameter measurements may provide a "non destructive" method of determining root dry matter. Further work will examine this question more closely.

Chez l'aubergine, du moins chez 3 variétés extrême-orientales et 3 méditerranéennes, la résistance stomatique de la face inférieure des feuilles reste toujours faible même sous un éclairement de 50 à 100 W.m-Z ; l'essentiel de la transpiration se fait probablement par la face inférieure des feuilles. Une expérience de greffage inter-écotypique montre que les racines ont une légère influence sur la résistance stomatique des feuilles quand le sol est maintenu très humide. En chambre climatisée, les résistances stomatiques des variétés d'aubergine extrême-orientales sont significativement inférieures à celles des variétés méditerranéennes lorsque les températures de l'air sont inférieures ou égales à 25 °C, c'est-à-dire dans les conditions thermiques qui prévalent pour des cultures sous serres. Par contre, aux températures supérieuresplus proches de celles qu'on trouve en culture estivale de plein champ — la différence de résistance stomatique entre les 2 écotypes s'atténue pour devenir nulle à 35 °C. Des mesures sur des cultures de plein champ ont confirmé ce résultat. Finalement, en culture irriguée de plein champ, les variétés méditerranéennes transpirent plus que les extrêmeorientales à cause de leur surface foliaire totale plus grande. Le surplus d'eau nécessaire est fourni grâce à leur système racinaire beaucoup plus développé. Cette meilleure exploitation des ressources en eau est la clef de leur rendement supérieur en culture irriguée de plein champ sous climat méditerranéen.Mots clés additionnels : Eclairement, température, humidité, racines. SUMMARY Agroclimatic factors influencing stomatal resistance of eggplant (Solanum melongena L.)Leaves of three eggplant varieties from the Far East and three from the Mediterranean always had low abaxial stomatal resistance, even under 50-100 W.m-z light ( fig. 1). Therefore, the major part of plant transpiration passed through the abaxial surface of leaves. An inter-ecotype grafting experiment showed that roots have a slight influence on leaf stomatal resistance if the soil is kept wet (fig. 4). In a climate chamber, eggplant varieties from the Far East (EO in text) had significantly lower stomatal resistances than those of Mediterranean varieties (M) at air temperatures less than 25 °C, i.e. under temperature conditions common in greenhouses. At higher temperatures closer to those prevailing in the field under summer irrigation, these differences between the two ecotypes decreased until by 35 °C they had completely disappeared ( fig. 3). This result has been confirmed by measurements in the field. Finally irrigated Mediterranean varieties in the open transpire more than their Far eastern counterparts by virtue of their greater leaf area per plant. This is possible because of their larger root systems which give access to a greater volume of stored soil moisture. This better exploitation of water resources is the key to their higher yield capacity under irrigation in a Mediterranean climate.

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