Ecophysiological Assessment of Sweet Potato Flowering and Tuber Development for Yield Optimization and Climate-Adaptive Cultivation in Romania

In the current climate change context and the potential to extend exotic crops in Romania, sweet potato could become an option for extensive areas with optimum ecophysiological conditions to provide economic and ecological benefits and assure food security. This study aimed to validate the suitability, photosynthetic performance, yield productivity, and sugar content of three sweet potato cultivars, KSC, Koretta, and Hayanmi, in Central Romania. Three key phenophases were selected: the beginning of flowering (P1), 50% tuber formation/full flowering (P2), and total tuber formation/leaves and stems bleached and dry (P3), respectively. At the beginning of flowering, extreme heat and moisture stress showed a reduced effect on the sweet potato development and photosynthetic parameters. The only exception was the assimilation rate for Hayanmi, which was markedly lower, with the highest relative chlorophyll content and leaf dry biomass. Koretta registered increased values for stomatal features. A higher tuber weight was registered for Hayanmi in P2 due to slightly increased rainfall and elevated evapotranspiration. In P3, the temperatures dropped sharply, rainfall exceeded evapotranspiration, and KSC accumulated a seven times higher value for tuber weight. The total biomass was 2–3 times higher for KSC in P3. Sugar content was negatively correlated with tuber weight, and Hayanmi had 1% higher values compared with KSC and Koretta. Sweet potato showed a variety-specific response to ecophysiological conditions, and for each variety, these physiological features suggest potential advantages for different cropping scenarios.