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

摘要

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 dayight temperature of 25/20 degrees C to 15/10 degrees 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 degrees C and 15/10 degrees C. At the lower temperature (15/10 degrees 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 degrees C) than at 25/20 degrees 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..