Intermittent water deficit in soil and micromorphology of the ora-pro-nóbis leaf epidermis

The amount of epidermal and stomatal cells in the leaves, stomatal density and stomatal index, can be modified under the influence of abiotic stresses. This study aimed to quantify the epidermal and stomatal cells on leaves of Ora-pro-nóbis plants ( Pereskia aculeata Mill.) subjected to growing intermittent water deficits in soil. Plants were grown in pots inside a greenhouse with intermittent variation of matric potential (MP) in the soil, in a completely randomized experiment with six replications and two plants per experimental unit, one plant per pot. The treatments consisted in adding to the pots a volume of water, calculated with basis on the water retention curve, to raise the matric potential to -5 kPa whenever the mean substrate matric potential reached values around -10 kPa, -30 kPa, -50 kPa, and -70 kPa. After 130 days of transplant, two sun-exposed leaves and two leaves of the region shaded by other leaves were selected from each plant, in position between 60 and 100 cm from the base of a budding cutting. Manual cuts were made, parallel to the adaxial and abaxial leaf surface, in the middle region of the leaf, which were washed with 70% ethanol and stained with 1% safranin. The images were obtained using a binocular optical micro scope with magnification of 400 times and captured by camera. We found that reducing intermittent matric potential on the substrate from -5 kPa to -70 kPa resulted in micromorphological changes in leaf epidermis due to the increase in the number of epidermal cells and decreased stomatal index on the adaxial side, but does not result in variation the number of stomatal cells and stomatal density on both faces of the leaves plant.Such modifications can explain the pro-nobis adaptation to water deficit conditions in the root zone.