Photosynthetic daily light integral, photoperiod, and temperature influence growth, development, and quality of Tecoma stans

Tecoma stans (L. Juss. Kunth) ‘Mayan Gold’ is a tropical flowering plant selected as a potential new greenhouse crop for its physical attributes and drought and heat tolerance. However, flower induction of new flowering crops can be challenging when environmental conditions during propagation and production are limiting (i.e. winter and early spring). The objectives of this study were to: (1) quantify the effects of photosynthetic daily light integral (DLI) during seed propagation (Expt 1.); (2) determine how photoperiod during the propagation and finish stages and temperature during the finish stage influence growth, flowering, and quality (Expt. 2); and (3) quantify and model the influence of DLI during both the propagation and finish stage of Tecoma (Expt. 3). Tecoma was propagated and finished under a wide range of mean DLIs (e.g., 0.75 to 26.6 mol·m −2·d−1) (Expt. 1 and 3), created by the combination of high-pressure sodium lamps (HPS) and fixed woven shade cloths of varying densities, propagated under four photoperiods (9, 12, 14, or 16 h), and forced at 18, 20, or 22 °C (Expt. 2). In Expt. 1, height, stem diameter, node number, leaf chlorophyll concentration, leaf fresh weight, leaf number, total leaf area, average individual leaf area, leaf area ratio, shoot and root dry mass, and root-to-shoot ratio increased as a quadratic function of DLI as DLI increased. In Expt. 2, under long day (LD) photoperiods (≥14-h), seedlings were taller than those propagated under 9-h photoperiods, while days to first open flower, shoot dry mass, and number of nodes below the terminal inflorescence were reduced. Time to first open flower was reduced as temperature increased. Conversely, number of visible buds and open flowers increased as temperature increased from 18 to 22 °C. In Expt. 3, the number of visible buds and branches, and shoot and root dry mass were primarily influenced by the mean finishing DLI. High-quality Tecoma seedlings and flowering plants were obtained when DLI was 14 to 16 mol·m −2·d−1 and 14 to 20 mol·m −2·d−1 during the propagation and finish stages, respectively. The most rapid, complete, and uniform flowering of Tecoma occurred when plants were propagated and finished under LD photoperiods and forced at 22 °C