A Low Cost and Nondestructive Micro-Pocket Meter on Chlorophyll Contents of Vegetable Leaves

Abstract

Highlights A meter on the contents of chlorophyll a and b and total chlorophyll of vegetable leaves was developed. Three LEDs as light sources and a light sensor to sense transmitted light through leaves. The models to predict the chlorophyll contents were established using multiple linear regression. The pocket detector makes chlorophyll content detection easy, fast, and in situ. Abstract. Detecting the contents of chlorophyll (chlorophyll a, chlorophyll b) is important to instruct vegetable growth. However, the traditional spectrophotometry used in measuring these contents requires expensive equipment, is destructive, time-consuming, toxic (acetone), and unable to measure in situ. To make the detection nondestructive, quick, cheap, safe, and on-site, a low-cost micro-pocket photosynthetic chlorophyll content meter was developed in this study. The meter consisted of a micro-controller of STC12C5A60S2, three light-emitting diodes at 460, 660, and 980 nm, a digital light sensor, three keys, one organic light-emitting diode display, and a power supply unit. The software was developed by using the C language. The leaves of leaf lettuce, garden sass, and spinach were used as samples. The models used to predict the contents of chlorophyll a, chlorophyll b, and total chlorophyll, as well as SPAD values, were established based on the absorbance of vegetable leaves at three wavelengths by using the multiple linear regression method. The root-mean-squares errors of the developed meter for chlorophyll a, chlorophyll b, total chlorophyll, and SPAD value were 0.068 mg/g, 0.024 mg/g, 0.085 mg/g, and 1.7, respectively. The meter was small in size and low in cost. The contents of chlorophyll a, chlorophyll b, total chlorophyll, and SPAD value, could be given in 2 s. Keywords: Absorbance, Chlorophyll a, Chlorophyll b, Chlorophyll content, Pocket meter, SPAD.