Elevated carbon dioxide (CO 2 ) influences photosynthesis ( A N ), transpiration (ET), and water use efficiency (WUE) for well‐watered potato ( Solanum tuberosum L.). Little is known regarding effects of short‐term drought and CO 2 . Two experiments, differing in the quantity of solar radiation, were conducted in soil‐plant‐atmosphere‐research chambers. Plants were grown at ambient (aCO 2 ) or twice‐ambient CO 2 (eCO 2 ) and received one of three irrigation treatments: no water stress (C), short‐term (11–16 d) water‐withholding during vegetative and post‐tuber initiation stages (VR), or post‐tuber initiation (R) only. Canopy conductance to CO 2 transfer (τ) and water vapor ( G v ), light use efficiency (α), daily A N , and ET decreased at the onset of each drought and were correlated with volumetric water content. The rate of decrease was similar for R and VR. G v declined more sharply than A N , resulting in higher WUE. Seasonal A N declined with the pattern of C > R > VR and was higher for eCO 2 C and R treatments. Seasonal WUE was higher for eCO 2 at all irrigation treatments. Total dry matter, harvest index, and leaf area were reduced ( p < 0.05) for droughted treatments and total dry matter and harvest index were also higher for eCO 2 VR pots. Relative responses to drought and CO 2 were similar among experiments, with greater magnitude of response under high solar radiation. Findings were similar to those reported under longer‐term water‐withholding studies, suggesting that interactions between CO 2 and drought on carbon assimilation and water use are conserved across production zones with varying radiation and rainfall patterns.
The composition and content of sugar play a pivotal role in goji berry (Lycium barbarum L.) fruits, determining fruit quality. Long-term exposure of goji berry to elevated CO2 (eCO2) was frequently demonstrated to reduce sugar content and secondary metabolites. In order to understand the regulatory mechanisms and improve the quality of fruit in the changing climate, it is essential to characterize sugar metabolism genes that respond to eCO2. The objectives of this study were to clone full-length cDNA of three sugar metabolism genes—LBGAE (Lycium barbarum UDP-glucuronate 4-epimerase), LBGALA (Lycium barbarum alpha-galactosidase), and LBMS (Lycium barbarum malate synthase)—that were previously identified responding to eCO2, and to analyze sequence characteristics and expression regulation patterns. Sugar metabolism enzymes regulated by these genes were also estimated along with various carbohydrates from goji berry fruits grown under ambient (400 μmol mol−1) and elevated (700 μmol mol−1) CO2 for 90 and 120 days. Homology-based sequence analysis revealed that the protein-contained functional domains are similar to sugar transport regulation and had a high sequence homology with other Solanaceae species. The sucrose metabolism-related enzyme’s activity varied significantly from ambient to eCO2 in 90-day and 120-day samples along with sugars. This study provides fundamental information on sugar metabolism genes to eCO2 in goji berry to enhance fruit quality to climate change.
