Effect of Free Air CO₂ Enrichment (FACE) on phenolic acid metabolism

Effect of elevated pCO₂ on phenolic acid metabolism in the leaves of winter wheat under low N (150 kg·hm^-2) and normal N (250 kg·hm^-2) levels was determined via FACE. The results show different impacts of elevated pCO₂ on the contents of salicylic acid, p-Hydroxybenzoic acid, cinamic acid, ferulic acid and vanillic acid, as well as phenylalnine ammonialyase (PAL) activity in winter wheat leaves under low N and normal N levels. At 1ow N level, salicylic acid, p-Hydroxybenzoic acid, cinamic acid, ferulic acid and vanillic acid are respectively significantly enhanced by 33.7%, 119.6%, 26.7%, 39.9% and 28.6% due to 30.9% increase in phenylalnine ammonialyase activity under elevated pCO₂. This, however, does not change significantly under normal N level. Hence the influence of elevated pCO₂ on phenolic acid metabolism in winter wheat leaf depends on N supply. It is highly important to determine appropriate fertilization rate in elevated CO₂ conditions. Furthermore, total phenol content shows the same variation trend as that of salicylic acid, p-Hydroxybenzoic acid, cinamic acid, ferulic acid and vanillic acid; and 79.6%~151.4% total phenol variation is caused by these acids changes. It then suggests that total phenol content increase in winter wheat leaf is partly accounted for enhanced phenolic acid metabolism under elevated pCO₂. Under low N level, the rise in atmospheric CO₂ may indirectly affect wheat-weed relationship by changing phenolic acid metabolism.