Mesure journaliére sur cycle végétatif complet des échanges gazeux: photosynthése, transpiration et respiration nocturne ?une culture de Maïs conduite sur colonnes de sol

Abstract

Abstract Daily measurement of gas exchanges during a complete growth cycle: photosynthesis, transpiration and night respiration in a soil culture of maize . During a complete growth cycle, photosynthesis (P), night‐respiration (R) and transpiration (T) have been measured daily for maize ( Zea mays L. cv. INRA F7 × F2) in a self‐regulating growth chamber. P and T varied according to three different kinetics. During the growing period there was a fast and concomitant variation of both P and T, which could be filled to a power function of time. During the fructification period we observed a linear decrease of P and T. Finally, during the senescence period P decreased to zero, whereas T kept a value higher than the evaporation of the naked soil. In the first two periods, the P/T ratio decreased as leaves aged. From this we could deduce that a slow increase of stomatal resistance (RS) and mesophyll resistance (RM) took place. R increased until the panicle appeared; it remained constant during fructification and then it decreased with senescence. Each nitrogen supply induced a transient increase of R. Finally, a water stress led to a greater decrease of P than of R, but the after effect of water stress disappeared a day later. These results were compared with those obtained in hydroponic conditions.