Design of artificial climate chamber for screening tea seedlings’ optimal light formulations

Abstract

A multi-channel photon sensor (MPS) capable of measuring Red Photon Flux Density (RPFD), Blue Photon Flux Density (BPFD) and Photosynthetic Photon Flux Density (PPFD) based on silicon photodiodes and filters is designed. At the same time, the FPGA-based environmental control system realizes the closed-loop control of RPFD, BPFD and PPFD by reading the data collected by the MPS that slides up and down according to the height of the canopy of the plant and using the PWM signal to control the LED light board’s red and blue channel. Based on the above method, the article completed an Artificial Climate Chamber (ACC) that realizes the automatic regulation of PPFD and RPFD/BPFD (R/B) of plant canopy that are the key parameters for determining the light formulations of plant lighting and environmental parameters including temperature, relative humidity, CO2 concentration, photoperiod etc. At a significantly lower cost, the MPS’s photon response curve is close to the ideal value, and the linear response R2 of the calibration exceeds 0.999. After setting the parameters for 30 s, the RPFD, BPFD and PPFD control error of the ACC are 1.43%, 1.39% and 0.71%, respectively. The paper also used tea seedlings as materials to explore the physiological and biochemical indexes of leaves under different R/B and PPFD. By comparing the biomass accumulation, free amino acid, tea polyphenols, polyphenols / amino acid ratio and other key parameters, PPFD = 100μmol∙m-2∙s-1 and R/B = 1/3 is the optimal light formulations for artificial light cultivation of tea seedlings.