Résumé
The objective of this study was to analyze the stomatal behavior along the day of Coffea Canephora genotypes after the water suspension period imposed in the irrigation system of the Cerrado. It was evaluated in the year of 2017 genotypes existing in the active Germplasm Bank located in the Brazilian Agrolivestock research company (Embrapa Cerrados), Planaltina-DF. Six genotypes of the species Coffea Canephora were used, 4 individuals selected from a breeding population of Embrapa Cerrados (8, 114, 30 and 125) and two clones with contrasting characteristics of drought tolerance (14 – Tolerant and 22-sensitive) (FERRÃO et al., 1999). The planting was carried out in lines, by material, using a spacing of 3.7 x 1.0 m in a system irrigated by central pivot, was performed in lines, by material, using a spacing of 3.7 x 1.0 m in a system irrigated by central pivot, with management of suspension of irrigation during the dry season, to synchronize the development of the floral buds ensuring high productivity and quality of the coffee. Irrigation was suspended for a period of 64 days (June 26 to August 28). Evaluation of Leaf stomatal conductance (CE-μmol m-2s-1) was performed using the porometer (SC-1, Decagon Devises), in the abaxial face of the leaves, at different evaluation times throughout the day (8:30, 10:30, 12:30, 14:30 and 16:30). The leaf water potential Ψw (Mpa) leaf, was measured in the period beforehand, with a Scholander pressure pump (PMS Instruments Plant Moisture - Model 1000). Measurements were taken at the end of the water suspension period. The lowest average values of water potential presented by genotypes 30 and 22, may indicate that they triggered a stomatic closure defense mechanism to reduce water loss during this period of stress, maintaining the lowest stotic conductance values throughout the day when compared to the others. On the other hand, the highest stotic conductance values observed in genotypes 8, 14, 114, and 125 are possibly associated with the highest mean values of foliar water potential as compared to 22 and 30. The present study concludes that the stomach conductance of the first hour of the morning is associated with the foliar water potential of the genotypes evaluated. Stomatic conductance oscillations observed throughout the day are possibly associated with the effect of water potential allied to climate variables.Different adaptation strategies to the water deficit imposed are observed due to the genetic variability of the evaluated materials.