Influence of Jasmonic acid on the response of pasture to ozone

A short-term (four-week) ozone-exposure experiment was conducted in 2014 to investigate the interactive effects of cutting on ozone-induced responses in white clover (Trifolium repens). Seedlings were propagated in early Spring 2014. After three weeks, to introduce a soil microbe, pots were inoculated with a soil slurry mixture. Pots were then divided between 3 treatments: uncut pots (controls), with a single cut to four centimetre (cm)m height immediately prior to ozone exposure and uncut, with a weekly application of Methyl-Jasmonate solution during the experiment. The seedlings were grown on for four weeks then exposed to random ozone profiles for four weeks.

A representative quarter of each pot was selected and recordings of healthy, injured or senesced leaves made on in weeks 2, 3 and 4. The harvest of above and below-ground biomass was performed after four weeks on each pot. Shoot biomass, and root biomass from a representative quarter of the pot, were dried for a minimum of 48 hours at 60 degrees Celsius. Root nodule biomass was also excised from the root system, and was air dried, sized and weighed. Root biomass, nodule mass and nodule numbers per pot were calculated. Leaf area index (LAI) of undamaged leaves was determined from dried forage. Mean injury and senescence data across the recordings was determined for each pot, and was arcsine transformed prior to analysis. Injury and senescence data, and selected biomass data, were then analysed by analysis of variance (ANOVA), with ozone background and treatment applied as factors.

Post-hoc Tukey's honest significant difference tests were used to determine the significance of factors where appropriate. Relationships between total root nodule biomass and biomass, and raw injury parameters for each treatment were also investigated via Pearson's correlation analysis. All analyses were conducted in R Software (version 3.1.2).

Data was first recorded in the field in field notebooks, and was then transferred to electronic copies (MS Excel worksheets). Data was then exported as .csv files for ingestion into the Environmental Information Data Centre.