Photoperiod, light, and temperature requirements to control plant architecture and flowering time in Salvia exserta

Abstract

SummarySalvia exserta is a native species of sub-tropical regions of South America that exhibits promising potential to become a novel ornamental crop. Because of the novelty of this genotype, data on the photoperiod, temperature, and light requirements to control vegetative growth and flowering time in this species are completely absent. The aim of this work was to study how plant architecture and flowering time in S. exserta plants were affected by different photoperiods between 8 – 18 h, various photosynthetically active irradiances between 250 – 1,470 µmol m–2 s–1, and temperatures between 17º – 26ºC, under greenhouse cultivation conditions. We also evaluated the effects of increasing the red:far-red (R:FR) ratio using a photoselective film. We demonstrated that photoperiods below 12 h, irradiances above 400 µmol m–2 s–1, and higher temperatures (i.e., 20ºC) accelerated flowering. Photoperiods above 8 h increased plant heights (by 22 – 55%), and the number of nodes was increased when plants were cultivated with 14 h of light. Higher irradiances (870 – 1,040 µmol m–2 s–1) reduced plant height by 20% and increased the number of lateral shoots three-fold. Higher temperatures (≥ 20ºC) reduced the number of lateral shoots by 50%. Plant architecture was significantly affected by light quality. A high R:FR ratio in the growing environment reduced plant height by 17%, doubled the number of lateral shoots, and delayed flowering. The results of our work suggest that controlling a few key environmental variables during cultivation is a low-cost and environmentally-friendly strategy to obtain high-quality S. exserta plants for commercial ornamental markets.