Effet de la temperature des racines sur leur respiration et sur la croissance des plantules de deux hybrides de maïs

L’effet de la température racinaire sur la respiration des racines et la croissance de la plante a été étudié, à court terme, sur de jeunes plants de maïs âgés de 14 j, pour un hybride de type denté et un hybride de type corné. Les résultats montrent que la modification de la température a un effet immédiat sur la respiration pour les deux hybrides. On ne constate de différences entre hybrides qu’au-delà d’un certain temps. D’une façon générale, la croissance de l’hybride de type denté est plus affectée par la température (15, 10 °C) que celle de l’hybride de type corné. Seuls les paramètres de croissance décrivant les racines permettent de différencier les deux génotypes.

The effect of root temperature on root respiration and growth was studied on 14-day old maize plants of two grain types (flint and dent). The plants were grown on nutrient solution in a growth cabinet at constant temperature (20 °C). At 14 days the plants were transfered to different root temperatures : 10, 15, 20 (control) and 25 °C. The study was carried out over 48 h. The mean level and the diurnal variation of root respiration increased with temperature. The variation of root respiration with temperature over the day and night was not uniform in the two types. Two-way variance analysis revealed that, for root respiration, i.e. production of elemental energy for other functions of the root system, the differences between genotypes were more in quick adaptation effect than in stress effect. For growth, the main differences were for the root system, dry matter accumulation and water content. In this case, the differences between genotypes were mainly in stress effect.