Vegetative Growth and Physiological Responses of Vanilla planifolia to Low-level LED Light Intensity in Controlled-environment Systems
Abstract
Light management is a critical factor influencing growth and physiological performance of Vanilla planifolia , a shade-requiring plant, yet quantitative information on the minimum irradiance required for vegetative development under controlled environments remains limited. The objective of our study was to evaluate whether low light-emitting diode (LED)–supplied irradiance can sustain vegetative growth and to compare the response of two genotypes under those conditions. Two V. planifolia genotypes (AG3 and Painter) in a controlled environment were subjected to two low-light intensities (160 or 360 µmol·m –2 ·s –1 photons corresponding to 8% or 18% of full sunlight, respectively) supplied by LED lighting for 15 months. Vine length, leaf number, basal stem diameter, and leaf chlorophyll index (LCI) were measured monthly. The maximum quantum efficiency of photosystem II [the ratio of variable chlorophyll fluorescence (Fv) to maximum chlorophyll fluorescence (Fm)] was recorded at month 10. Genotype influenced vegetative growth significantly, with ‘AG3’ exhibiting greater vine length, leaf number, and basal stem diameter than ‘Painter’. Increasing irradiance from 8% to 18% of full sunlight did not affect growth variables significantly. However, plants grown under 8% light exhibited greater LCI values and a greater Fv-to-Fm ratio compared with those grown under 18% light, indicating greater photochemical efficiency under lower irradiance. These results suggest that the low irradiance levels provided by low-intensity LED lighting may be sufficient to sustain vegetative growth of V . planifolia in controlled-environment agriculture. Future research should evaluate a broader range of irradiance levels, extend monitoring into the reproductive phase, and assess yield and pod quality to refine irradiance recommendations for full-cycle indoor vanilla production on a commercial scale.