Method for obtaining CO2 limit point of Light-use efficiency model based on U-chord curvature

Abstract

Abstract. As a plant photosynthetic raw material, CO2 has a great effect on the photosynthesis and light-use efficiency (LUE) of tomatoes. Aiming at the problem of low light energy and CO2 utilization efficiency under artificial lighting such as artificial climate room, this paper proposes a CO2 control scheme based on optimizing the light energy utilization rate of artificial light sources. Hydroponic tomatoes under 4 gradient artificial side light sources were used as test materials. By designing the instant photosynthetic rate and LUE under the conditions of nested test with temperature and CO2 concentrations ([CO2]), the support vector regression (SVR) algorithm was used to construct a prediction model of LUE. The U-chord curvature method was used to calculate the CO2 curvature value of the LUE- CO2 curve under different temperature and [CO2]. The hill-climbing method was used to obtain the maximum curvature value points regarded as the limit point for the higher efficiency of [CO2] for LUE. The temperature and the [CO2] of limit value point (Lvp- [CO2]) were fitted in different light intensities. The results showed that the determination coefficients of the prediction models under the four light gradients reach 0.9872, 0.9965, 09990, and 0.9992, respectively, with the root mean square errors of 0.00063, 0.00022, 0.00009 and 0.0001μmol·mol-1. Additionally, the Lvp- [CO2] would increase with the soaring of temperature as well as [CO2] to LUE. Before the Lvp- [CO2], the increasing unit [CO2] was quickly and efficiently increased the LUE while the efficiency decreased above the Lvp- [CO2]. Therefore, the Lvp- [CO2] can be a suitable target value for CO2 regulation, and provide a theoretical basis for the regulation of LUE in artificial lighting.