phs-202203-0014 ArticleInAPeriodical 2022 Photosynthetica 60 3 https://ps.ueb.cas.cz/artkey/phs-202203-0014.php https://doi.org/10.32615/ps.2022.040 457-464 NOMURAK. SAITOM. ITOM. YAMANES. IWAOT. TADAI. YAMAZAKIT. ONOS. YASUTAKED. KITANOM. Diurnal decline in the photosynthetic capacity of uppermost leaves in an eggplant canopy grown in a horticultural greenhouse Parameters representing leaf photosynthetic capacity, namely, the maximal carboxylation rate (V<sub>cmax</sub>), maximal electron transport rate (J<sub>max</sub>), and triose phosphate-utilization rate (T<sub>p</sub>), can vary depending on various factors. The present study investigated diurnal variations in V<sub>cmax</sub>, J<sub>max</sub>, and T<sub>p</sub> of uppermost leaves of soil-grown, well-watered eggplant in a greenhouse based on the simultaneous measurements of leaf gas exchange and chlorophyll fluorescence. The values of net photosynthetic rates and electron transport rates plotted against intercellular CO<sub>2</sub> concentrations were noticeably higher in the morning than in the afternoon. Significant differences were detected among the values of V<sub>cmax</sub>, J<sub>max</sub>, and T<sub>p</sub> obtained at different times of day (08:30, 11:00, 13:30, and 16:00 h). All three parameters tended to decline as the time of day advanced; compared to the values at 08:30 h, V<sub>cmax</sub>, J<sub>max</sub>, and T<sub>p</sub> declined by approximately 15% at 16:00 h. Among the three parameters, T<sub>p</sub> appeared to be the most sensitive to time.