Annabelle Larmure

How does temperature affect C and N allocation to the seeds during the seed-filling period in pea? Effect on seed nitrogen concentration

The effect of moderate temperature on seed N concentration during the seed-filling period was evaluated in pea (Pisum sativum L.) kept in growth cabinets and the relation between plant assimilate availability and the variation of seed N concentration with temperature was investigated. Seed N concentration of pea was significantly lowered when temperature during the seed-filling period decreased from a day / night temperature of 25 / 20°C to 15 / 10°C. Our results demonstrate that during the seed-filling period mechanisms linked with assimilate availability can modify seed N accumulation rate and / or seed-filling duration between 25 / 20°C and 15 / 10°C. At the lower temperature (15 / 10°C), an increased C availability resulting from an enhanced carbon fixation per degree-day allowed new competing vegetative sinks to grow as pea is an indeterminate plant. Consequently N availability to filling seeds was reduced. Because the rate of seed N accumulation per degree-day mainly depends on N availability to filling seeds, the rate of seed N accumulation was lower at the low temperature of our study (15 / 10°C) than at 25 / 20°C while seed growth rate per degree-day remains unaffected, consequently seed N concentration was reduced. Concomitantly, the increased C availability at the lower temperature prolonged the duration of the seed-filling period.

Changes in seed composition and germination of wheat (Triticum aestivum) and pea (Pisum sativum) when exposed to high temperatures during grain filling and maturation

Abstract. Most studies on the effects of climate change have been conducted on grain yield and composition; few have focused on seed germination and storage ability, especially in temperate crops. However, projected higher temperatures at the end of crop cycle are expected to affect not only seed nutritional quality but also seed germination and storage ability. In this study, experiments were conducted on wheat (Triticum aestivum L.) and pea (Pisum sativum L.) in controlled conditions to assess the effects of high maximum daytime temperatures, between 25°C and 35°C, on mother plants during grain filling or only during grain desiccation. Grain composition and seed characteristics related to germination and seed storage were investigated. When the stress occurred during grain filling, seed dry weight decreased, and protein and total fatty acid concentrations increased. Higher contents of vicilins in pea and polyunsaturated fatty acids in both crops were observed. Total starch content decreased in wheat. Sucrose : oligosaccharides ratio decreased, seed conductivity increased and germination was altered in both crops whenever the stress occurred. All of these modifications were mainly detrimental to the seed nutritional and end-use values. Further investigations should be carried out to assess genetic diversity, to characterise other species, and to introduce the impact of high temperatures on these seed characteristics into crop models.