Effects of accelerated aging and p-coumaric acid on crimson clover (Trifolium incarnatum L.) seed germination

Several phenolic acids, including p-coumaric acid, have been described as allelochemicals that may inhibit seed germination or seedling growth. Whether these effects are exacerbated in forage species by environmental stressors is unknown. Accelerated seed aging [high temperature (41°C) and high humidity (100%)] reduces germination and seedling vigour and provides some indication of seed germination and seedling performance under stress conditions (e.g. temperature and water stress). Thus, accelerated aging provides a means to determine how seed “age” might affect germination or seedling vigor in response to a stressor. Here we compare responses of aged and non-aged seed of crimson clover (Trifolium incarnatum L.) to p-coumaric acid at 10⁻⁵ and 10⁻³ M concentrations. Accelerated aging delayed and reduced crimson clover seed germination. The mean germination for 0, 24, 48, and 72 h aging treatment was 93%, 73%, 40%, and 15% respectively, and by 96 h most of the germination had occurred. Un-aged seed germination appeared to be slightly stimulated by 10⁻³ M p-coumaric acid concentration, while, the 10⁻⁵ M p-coumaric acid concentration reduced the seed germination. When accelerated aging was combined with the p-coumaric acid treatments, there were significant differences as to accelerated aging by p-coumaric acid treatment interactions. Accelerated aging for 24 h followed by p-coumaric acid further reduced the germination. At 48 h accelerated aging, there was no significant difference as to p-coumaric acid, probably due to the overwhelming effect of accelerated aging. These results showed that accelerated aging, as a proxy for increased physiological age, could make seed more susceptible to an allelochemical at concentration levels generally found in the soil.