Biomass allocation and organs growth of cucumber (Cucumis sativus L.) under elevated CO2 and different N supply

This article studied the effects of nitrogen (N) and CO2 enrichment on biomass and N accumulation and partitioning of cucumber grown in open top chambers. At the seedling stage, elevated CO2 increased the biomass and N content of the entire plant. The root had the largest increase in biomass and N content among the organs and more biomass allocation. The largest drops of N concentration showed in root at moderate and high N, in leaf at low N, respectively. Elevated CO2 increased stem biomass allocation at moderate and high N, but decreased leaf biomass allocation at all N levels. At the initial fruit stage, the response to elevated CO2 of biomass and N content decreased. Elevated CO2 increased biomass allocation to leaf and resulted in the largest drop of leaf N concentration at low and moderate N supply. High N supply promoted biomass production and N reallocation from the leaf to fruit, but decreased leaf biomass allocation. Thus, biomass allocation is initially affected by root-shoot growth balance to adapt to enriched CO2, leading to the largest root growth, then biomass allocates to another sink (stem). Long exposure of elevated CO2 results in photosynthetic acclimation in deficient N supply, which probably attributes to excessive stem and leaf biomass allocation and shortage of fruit storage. But high N shifts biomass allocation from leaf to fruit. Practically, sufficient N supply is needed for an efficient transport of carbohydrates to fruits and increases the yields under elevated CO2.