VARIACIÓN ESTOMÁTICA EN FOLIOLOS DE NOGAL PECANERO (Carya illinoensis (WANGENH.) K. KOCH) EN BASE AL MÉTODO Y EFICIENCIA DE RIEGO

This study aimed to determine the physiological mechanisms in the tree adaptation process when different technologies are employed in order to irrigate the crop. Pecan nut leaf samples were collected in an orchard where irrigation is applied by means of four systems: surface, sprinkler, micro sprinkler and drip irrigation. Under the different irrigation methods a branch was selected and divided into three parts: basal, middle and apical; then, three compound leaves were collected in order to collect three leaflets from the same branch segments. Image analysis was used to characterize and quantify the stomata and leaf area from scanned images. Trees irrigated with the sprinkler system showed a higher leaf area in composite apical leaves and in the leaflets of the apical part of the compound leaf. In the trees under all four irrigation systems predominated medium size stomata (0.0025-0.0050mm^sup 2^). Changes in the stomata location were observed, with a trend from the apical to the basal part of the branch as the wet soil volume decreased. The study revealed the crop adaptation mechanisms in response to the volume variation applied through different irrigation methods by modifying the density, location and size of stomata, allowing to stabilize the photosynthetic rate and transpiration demand needed for survival and reproduction of the tree.