Tissue Osmotic Potential and Membranes Permeability of Nopalitos (Opuntia spp.) Affected by Changes in Soil Water Potential

Abstract

The effects of environmental factors on physiological characteristics of nopalito are scarcely known in nature and farms. The effect of the soil water potential (?W) on osmotic potential (??) and membranes permeability (damage index, ID) under greenhouse conditions were evaluated in five cultivars and one wild accession of nopalitos. A completely randomized design, with one plant as an experimental unit and six replications, per treatment, were used. Following a 60-day drought treatment, the osmotic potential diminished exponentially, on average from -0.24 up to -1.33 MPa in the wild accession O. streptacantha while cv. Copena V1 reached the maximum reduction, from -0.30 to -1.48 MPa, as soil ?W decreased from -0.39 up to -3.27 MPa. At -3.27 MPa of soil ?W, the ID ranged among cultivars from 3.5% in cv. Solferino up to 29.0% in cv. Moradaza. It is concluded that changes in ?? of nopalitos may be an intrinsic physiological characteristic to distinguish Opuntia plants. The high tolerance of Opuntia spp. to soil water deficit, for a relatively long time (60 days), is defined, among several metabolic modifications, by small changes of ?? and minimum cellular membranes damage.