Potassium-enriched clinoptilolite zeolite mitigates the adverse impacts of salinity stress in perennial ryegrass (Lolium perenne L.) by increasing silicon absorption and improving the K/Na ratio

Abstract

Salinity is a major abiotic stress that adversely affects turfgrass growth. Clinoptilolite zeolite, a silicon (Si)-rich mineral, may allow these plants to cope with salinity. Therefore, in the present study, the effects of ordinary clinoptilolite zeolite (OZ) and potassium-enriched clinoptilolite zeolite (K-EZ) on the growth of perennial ryegrass (Lolium perenne L.) were assessed under salinity stress. Perennial ryegrass seeds were cultured in soil mixtures amended, or not, with OZ or K-EZ, then exposed to three salinity levels (0, 50 or 100 mM NaCl) for three months. Control plants were grown in the same soil mixture without zeolites, but not exposed to salinity. In salinity, the application of both types of zeolite significantly decreased Na content by 44.36% and 21.31%, but increased K content by 272.34% and 81.59%, as well as the K/Na ratio by 590.47% and 129.43%, in shoots and roots, respectively, compared to the no-zeolite treatment. Similarly, Si content in shoots increased by 28.33%. Amending the soil mixture with zeolite, especially K-EZ, enhanced relative water content, membrane stability index, total chlorophyll content, total soluble proteins, peroxidase and superoxide dismutase activities but reduced the contents of total soluble carbohydrates, hydrogen peroxide, and malondialdehyde in saline conditions. Shoot and root dry weight, root volume and root/shoot ratio also improved. Soil amendment with both forms of zeolite, as a Si-rich mineral, partially offset the negative impacts of salinity on perennial ryegrass, although K-EZ had more noticeable positive and beneficial effects. The amendment of growth media with zeolite may be an effective sustainable management practice for turfgrass used in landscaping and sports fields exposed to saline water.