Effects Of Plant Growth Regulators Foliar Application On Perennial Ryegrass Responses To Drought Stress And Cold Stress

Foliar application of PGRs is an effective strategy for modern turfgrass managers. PGRs have many effects on turfgrass including reducing plant height, increasing turf density, promoting green colors, improving turf quality, and enhancing specific plant physiological metabolism rate and ultimately increasing grass tolerance towards stress.The objectives of this study were to investigate the effects of Trinexapac-ethyl(TE), abscisic acid(ABA), and salicylic acid(SA) on N-rich compound, total non-structural carbohydrate (TNC) and antioxidant enzymes in perennial ryegrass (Lolium perenne L) under cold stressed conditions. Every2weeks,’Peak’ Perennial Ryegrass were foliar sprayed with Primo maxx at1.95ml/L or ABA at100umol/L or SA at50umol/L before cold stress and were sprayed twice in total. And then plants were exposed to cold stressed conditions in growth chambers. Results showed that TE pretreatment group maintained higher nitrogen compounds contend higher carbohydrates content, higher levels of antioxidant enzyme activity and better turf quality during28days of cold stress compared with the untreated control group. When the stress initiated, TNC content was lower in TE-treated plants (24.4mg/g DW) than in control plants (26.5mg/g DW). After7days of treatment, the TNC change pattern was reversed. We concluded that TE can improve the cold resistance of perennial ryegrass. Cold resistance was not improved for both ABA-pretreatment group and SA-pretreatment group..For drought stress study, TE(1.95ml/L Primo Maxx) and ABA(100umol/L ABA)were sprayed once every2weeks (3times in total).In addition, ABA was sprayed once a week during drought stress treatment. Foliar application of TE or ABA promoted higher leaf relative water content, and better membrane stability (lower EL) which suggested that application of TE or ABA could improve drought tolerance of perennial ryegrass. Higher soluble sugar content in TE-treated plants during drought stress may due to the better photosynthesis machinery with higher level of chlorophyll content induced by TE application. Untreated control plants showed relatively poor drought tolerance with higher level of proline content in the late days of stress treatment which suggested proline was not the major osmotic regulation substance for severe drought stress in perennial ryegrass. TE and ABA treated plants also maintained higher levels of POD and CAT activity which provided better antioxidant protection from drought induce dreactive oxygen leading to less Electronic leakage.