CO2 response in nitrogen concentration of seeds, embryo and albumen in rice cultivars grown at free-air CO2 enrichment (FACE)

Seed quality is a key characteristic for plant life for their fitness and also important for human and animal as a food source. Previous studies have shown that seed nitrogen concentration ([N]) decreases at elevated [CO₂] in grass species such as rice and wheat whereas legumes and other dicot species exhibit less or no decrease in seed [N]. We hypothesized that the difference in CO₂ response of seed [N] came from the difference in seed structure; seed of grass species consists of embryo and albumen whereas seeds of most of the dicot species consist only of the embryo, and therefore, CO₂ response may be different between [N] of albumen and embryo. Here, we examined [N] in seed, albumen and embryo in eight cultivars of rice grown at free-air CO₂ enrichment (FACE). There was a significant variation in CO₂ response of seed [N] among rice cultivars. The reduction of seed [N] by elevated [CO₂] was significantly correlated to the decrease in the albumen [N], but not with the embryo [N]. As expected, embryo [N] was less responsive to elevated [CO₂]. It is concluded that presence of albumen and CO₂ response in albumen [N] may be a key for understanding variation in seed [N] response to elevated [CO₂] among species and among cultivars. 

Key Words: elevated [CO₂], seed, nitrogen, albumen, embryo, rice.

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