Discrete nutrient utilizations in two Bauhinia species exposed to supplemental light-emitting diode spectra and exponential fertilization

Abstract

Bauhinia is a widely planted urban tree plant in tropical cities, which are frequently dwelling in a habitat exposed to inevitable streetlamp lighting. It is of practical meaning to figure out the lighting spectra that benefit nutrient utilization in corporation with a proper exponential fertilization regime. In this study, Bauhinia brachycarpa and B. variegata seedlings were cultured with exponential fertilization at the rate of 80 mg nitrogen (N) plant-1 (N-phosphorus-potassium, 10-7-9) with an unfertilized control, and both were exposed to light-emitting diode spectra of R1BG5 (13.9% red, 77.0% green, 9.2% blue), R2BG3 (26.2% red, 70.2% green, 3.5% blue), and R3BG1 (42.3% red, 57.3% green, 0.4% blue). The R3BG1 spectrum resulted in smaller growing size and dry mass but higher nutrient concentration and root water content compared to the other two spectra. Exponential fertilization increased fresh mass for two Bauhinia species but only increased dry mass in B. brachycarpa. Compared to B. variegata, B. brachycarpa was verified to have a higher capacity to accommodate exogeneous nutrient input through exponential fertilization. The R3BG1 spectrum was recommended for the illumination in streetlamps for Bauhinia because this spectrum can promote nutrient uptake without too fast rate of growth relative to other spectra with lower red-light proportions.