Salinity response of Kentucky bluegrass (Poa pratensis L.) as influenced by salicylic acid and progesterone

Abstract

The effect of salicylic acid (SA) and progesterone (P4) on physiological and biochemical parameters of Kentucky bluegrass under salinity stress was assessed. A factorial experiment was established based on a randomized complete block design with four replications, under greenhouse conditions. The experimental treatments included four levels of salinity (0, 2, 4 and 6 dS · m-1) and two plant growth regulators (P4 and SA) at six levels including the control (1 and 10 mg · L-1 P4, 1 and 3 mM SA, and 1 mg · L-1 P4 + 1 mM SA). The increase in salinity impaired the quality of grass, but SA and P4 application alleviated the impacts of salinity and ameliorated the quality of grasses under salinity. The highest electrolyte leakage was observed under 6 dS.m-1 salinity and 3 mM SA. The application of SA and P4 improved the carotenoid content in bluegrass subjected to saline stress compared to plants not treated with growth regulators. The highest total chlorophyll content was obtained from 2 dS · m-1 salinity and 10 mg · L-1 P4. Leaf proline content was increased with salinity level. However, slight differences existed between different levels of growth regulators. The SA and P4 increased proline content. Salinity increased the concentration of malondialdehyde (MDA) in the grass from 12 to 50 %, and growth regulators helped to reduce this concentration. Also, an increase in peroxidase activity with 6 dS · m-1 salinity was observed when SA and P4 were applied simultaneously. Overall, it was observed that SA and P4 increased salinity tolerance through enhancing grass quality, chlorophyll, and carotenoid content and scavenging free oxygen radicals through influencing antioxidant enzymes.