Pineapple stem-derived bromelain based priming improves pepper seed protein reserve mobilization and germination

Abstract

Pepper fruit has a great agronomic, nutritional and commercial value given that it is rich in antioxidant compounds such as carotenes, and vitamins C and E. However, pepper seeds are slow to germinate and emergence is often non-uniform and incomplete. Seed priming and invigoration treatments have been explored for a number of pepper varieties but success has been variable and generally limited. The present report describes the effects of pineapple stem – derived protease (stem bromelain) based priming on pepper seed germination in relation to reserve mobilization (specifically, proteins and aminoacids). Germination capacity in bromelain treated seeds was significantly higher on days 7, 14 and 21 than in unsoaked (control) and deionized water-soaked seeds but comparable across the treatments and the control on day 28. Germination rate was significantly highest in bromelain treated seeds. Light microscopy revealed an abundance of protein bodies in the endosperm of the seeds investigated at before imbibition and when observed over a period of 96 h, these bodies were progressively degraded, with the rate of this degradation being fastest in bromelain treated seeds. Quantitative measurements of protein levels (and free amino content) confirmed this observation. The results motivate the use of bromelain extracts for priming pepper seeds based on their proteolytic activity, since germination is dependent on the availability of crude protein and essential amino acids.