Potassium enhances frost tolerance in young individuals of three tropical dry forest species from Mexico

Movement of species outside their range of distribution could be a strategy for conservation purposes, but before implementation, it is necessary to evaluate plants responses to the conditions that they will experience in new locations. We evaluated the effect of potassium fertilisation to enhance the frost tolerance of young individuals of Albizia plurijuga (Standley) Britton & Rose, Cedrela dugesii S. Watson and Ceiba aesculifolia (Kunth) Britten & Baker f., which are all common species from tropical dry forests in Mexico. Plants were propagated in a shade-house and fertilised during 9 months with different concentrations of potassium (39, 189 and 528 ppm). In frost simulations, plants were exposed to temperatures below 0 degrees C during different time periods and frost injury was assessed by electrolyte leakage of leaf discs from young and old leaves. We observed that potassium fertilisation enhanced frost tolerance by reducing electrolyte leakage mainly in young leaves. We recorded plant re-sprouting ability after exposure to subzero temperatures over 45 days, finding notable differences among species: all individuals of C. dugesii sprouted, followed by some of A. plurijuga and finally just one of C. aesculifolia. Also, high potassium levels increased re-sprouting response. These species have a low frost tolerance, but potassium fertilisation seemed to be effective to enhance it for young individuals, increasing the probability of survival if plants are moved to colder areas than current habitats.