Elevated CO induces age-dependent restoration of growth and metabolism in gibberellin-deficient plants.

The effect of elevated [CO] on the growth of tomato plants with reduced gibberellin content is influenced by developmental stage. The impact of increased atmospheric carbon dioxide (CO) on plants has aroused interest in the last decades. Signaling molecules known as plant hormones are fundamental controllers of plant growth and development. Elevated CO2 concentration ([CO]) increases plant growth; however, whether plant hormones act as mediators of this effect is still an open question. Here, we show the response to elevated [CO] in tomato does not require a functional gibberellin (GA) biosynthesis pathway. We compared growth and primary metabolism between wild-type (WT) and GA-deficient mutant (gib-1) plants transferred from ambient (400 ppm) to elevated (750 ppm) [CO] at two different growth stages (either 21 or 35 days after germination, DAG). Growth, photosynthetic parameters and primary metabolism in the stunted gib-1 plants were restored when they were transferred to elevated [CO] at 21 DAG. Elevated [CO] also stimulated growth and photosynthetic parameters in WT plants at 21 DAG; however, only minor changes were observed in the level of primary metabolites. At 35 DAG, on the other hand, elevated [CO] did not stimulate growth in WT plants and gib-1 mutants showed their characteristic stunted growth phenotype. Taken together, our results reveal that elevated [CO] enhances growth only within a narrow developmental window, in which GA biosynthesis is dispensable. This finding could be relevant for breeding crops in the face of the expected increases in atmospheric CO over the next century.