Effects of Climate Change Scenarios on Growth, Flowering Characteristics, and Honey Production Potential of Pseudolysimachion rotundum var. subintegrum

Climate change significantly influences plants' physiology, flowering phenology, and nectar production, affecting pollinator interactions and apicultural sustainability. This study examines the physiological responses of <i>Pseudolysimachion rotundum</i> (Nakai) Holub var. <i>subintegrum</i> (Nakai) T.Yamaz. (Plantaginaceae) under projected climate change scenarios, focusing on flowering traits, nectar secretion, and honey production potential. Elevated CO₂ levels enhanced its net photosynthesis and water-use efficiency, supporting sustained carbohydrate assimilation and promoting aboveground biomass accumulation. However, the increased nitrogen demand for vegetative growth and inflorescence production may have led to reduced allocation of nitrogen to the nectar, contributing to a decline in its amino acid concentrations. The flowering period advanced with rising temperatures, with peak bloom occurring up to four days earlier under the SSP5 conditions. While the nectar secretion per flower remained stable, an increase in floral abundance led to a 3.8-fold rise in the estimated honey production per hectare. The analysis of the nectar's composition revealed that sucrose hydrolysis intensified under higher temperatures, shifting the nectar toward a hexose-rich profile. Although nectar quality slightly declined due to reductions in sucrose and nitrogen-rich amino acids, phenylalanine-the most preferred amino acid by honeybees-remained dominant across all scenarios. These findings confirm the strong climate resilience of <i>P. rotundum</i> var. <i>subintegrum</i>, highlighting its potential as a sustainable nectar source in future apicultural landscapes. Given the crucial role of nitrogen in both plant growth and nectar composition, future research should explore soil nitrogen dynamics and plant nitrogen metabolism to ensure long-term sustainability in plant-pollinator interactions and apicultural practices.