ABA and BAP improve the accumulation of carbohydrates and alter carbon allocation in potato plants at elevated CO.

Elevated CO interactions with other factors affects the plant performance. Regarding the differences between cultivars in response to CO concentrations, identifying the cultivars that better respond to such conditions would maximize their potential benefits. Increasing the ability of plants to benefit more from elevated CO levels alleviates the adverse effects of photoassimilate accumulation on photosynthesis and increases the productivity of plants. Despite its agronomic importance, there is no information about the interactive effects of elevated CO concentration and plant growth regulators (PGRs) on potato ( L.) plants. Hence, the physiological response and source-sink relationship of potato plants (. Agria and Fontane) to combined application of CO levels (400 vs. 800 µmol mol) and plant growth regulators (PGR) [6-benzylaminopurine (BAP) + Abscisic acid (ABA)] were evaluated under a controlled environment. The results revealed a variation between the potato cultivars in response to a combination of PGRs and CO levels. Cultivars were different in leaf chlorophyll content; Agria had higher chlorophyll a, b, and total chlorophyll content by 23, 43, and 23%, respectively, compared with Fontane. The net photosynthetic rate was doubled at the elevated compared with the ambient CO. In Agria, the ratio of leaf intercellular to ambient air CO concentrations [C:C] was declined in elevated-CO-grown plants, which indicated the stomata would become more conservative at higher CO levels. On the other hand, the increased C:C in Fontane showed a stomatal acclimation to higher CO concentration. The higher leaf dark respiration of the elevated CO-grown and BAP + ABA-treated plants was associated with a higher leaf soluble carbohydrates and starch content. Elevated CO and BAP + ABA shifted the dry matter partitioning to the belowground more than the above-media organs. The lower leaf soluble carbohydrate content and greater tuber yield in Fontane might indicate a more efficient photoassimilate translocation than Agria. The results highlighted positive synergic effects of the combined BAP + ABA and elevated CO on tuber yield and productivity of the potato plants.