Seed oil content and phenology of Physaria species (Brassicaceae) differing in their life-cycle

Abstract

Phenology of reproduction influences the concentration of the oil in the seeds, through changes in grain filling dynamics and biosynthetic activity. The objective was to evaluate differences in seed quality and phenology among species of Physaria differing in life-cycle: annuals-P. gracilis and P. angustifolia; and perennials- P. pinetorum and P. mendocina. The effect of the timing of the seed filling on seed weight and oil content in a common garden experiment in Patagonia, Argentina, was evaluated. Both annual species bloomed earlier and had a shorter and compressed growth-cycle, than the perennials. P. mendocina showed longer phenological phases and bloomed and started the fruit ripening stage later, while P. pinetorum had an intermediate duration of the flowering-fruiting stages. Seed yield was 25 % higher in annuals, but oil concentration and oil-yield were not related to life-cycle. P. gracilis and P. mendocina produced seeds with higher oil content that those reported for the commercial species Physaria fendleri. Higher temperature during seed-filling influenced oil accumulation in the seed. The seed oil content of P. mendocina, remained stable throughout the season while in the other three species it tended to decrease over time as temperature increased, in an inverse relationship between temperature and oil content. Indirect effects of temperature on growth components such as premature senescence or low photosynthetic capacity could also explain these trends. Seed weight was stable in time in all species. Selection of early maturing plants should improve oil-content only in those species in which oil-content is temperature-dependent (i.e. annuals and P. pinetorum) or is affected by a reduction in the capacity of the source to produce carbohydrates. The source-sink ratio and the plant´s internal balance of carbohydrates, including reserves could play an important role in the regulation of grain quality.