Effects of Daily Light Integral on Growth, Chlorophyll Fluorescence, and Flowering in Episcia

Abstracts Optimizing light conditions is crucial for Episcia production. This study examined the effects of daily light integrals (DLIs) from 8-hour short-day (SD) and 16-hour long-day (LD) photoperiods, combined with varying photosynthetic photon flux densities, on the growth, physiology, and flowering of two Episcia cultivars: Lemon Aide (green leaves) and Choco Brown Soldier (brown leaves). As DLI increased, leaf number in ‘Lemon Aide’ rose continuously, whereas ‘Choco Brown Soldier’ plateaued at 5.8 mol·m –2 ·d –1 . Both cultivars peaked in total leaf area at 5.8 mol·m –2 ·d –1 , after which it declined. Average leaf area and leaf soil plant analysis development (SPAD) values decreased with increasing DLI, with ‘Lemon Aide’ showing more pronounced yellowing at greater DLIs. Leaf thickness increased with increasing DLI, accompanied by greater anthocyanin accumulation in ‘Choco Brown Soldier’. Stolon number increased with DLI, peaking at 5.8 to 8.6 mol·m –2 ·d –1 . At 5.8 mol·m –2 ·d –1 , both cultivars produced more stolons under SD conditions than LD, but no significant photoperiod effect was observed at 2.9 mol·m –2 ·d –1 . Chlorophyll fluorescence parameters including minimal fluorescence (Fo), maximal fluorescence (Fm), effective quantum yield of photosystem II (PS II) photochemistry (ΦPSII), and maximum quantum efficiency of PSII (Fv/Fm), declined with increasing DLI, with ‘Choco Brown Soldier’ consistently exhibiting higher values, particularly at DLIs > 8.6 mol·m –2 ·d –1 . Flowering occurred in ‘Choco Brown Soldier’ at DLIs ≥ 2.9 mol·m –2 ·d –1 , with flower number increasing at 5.8 mol·m –2 ·d –1 under LD conditions and plateauing at 8.6 mol·m –2 ·d –1 . In contrast, ‘Lemon Aide’ did not flower during the 145 days treatment period.