Elevated Carbon Dioxide only Partly Alleviates the Negative Effects of Elevated Temperature on Potato Growth and Tuber Yield

The current rapid increase in ambient carbon dioxide concentration ([CO₂]) and global temperatures have major impacts on the growth and yield of crops. Potato is classified as a heat-sensitive temperate crop and its growth and yield are expected to be negatively affected by rising temperatures, but it is also expected to respond positively to increasing ambient [CO₂]. In this study, we investigated the physiological, growth, and yield responses of two potato cultivars to elevated temperature (eT) and the possible role of elevated [CO₂] (e[CO₂]) in counteracting the negative effects of eT. Two growth chamber trials (trials 1 and 2) were conducted using two temperature regimes: ambient temperature (aT, T_min/T_max = 12/25 ℃) and eT (T_min/T_max = 15/38 ℃), and two [CO₂]: ambient (a[CO₂]) = 415 ppm and e[CO₂] = 700 ppm. Temperatures gradually rose from the minimum at 6.00 AM to reach T_max at noon, then T_max was maintained for 1 h in trial 1 and for 4 h in trial 2. Elevated [CO₂] increased photosynthesis (Anet) in both cultivars at aT and eT. Elevated temperature also stimulated Anet compared to aT. Elevated [CO₂] significantly reduced stomatal opening size, while eT resulted in larger stomata openings and higher stomatal conductance. Elevated [CO₂] increased tuber yields at aT in both trials. Tuberisation was delayed by eT in trial 1, and completely inhibited in trial 2 even at e[CO₂], resulting in no tuber yield. The two cultivars responded similarly to treatments, but Mondial initiated more tubers and had higher tuber yield than BP1. The results suggest that potato will benefit from e[CO₂] in future, even when exposed to high T_max for a short period of the day, but the benefit will be eroded when the crop is exposed to high T_max for an extended period of the day.