###### Abstract  
Aeroponics is a soilless cultivation technology integrating plant nutrition, physiology, ecological environment, agricultural automation and horticulture. One of the soilless advantages is that a non-invasive observation of the root system growth development is possible. This paper presents a vegetative growth evaluation of lettuce plants in an aeroponic chamber, where root and leaf development parameters were measured in three lettuce crops through plant images captured in the visible (VIS), near infrared (NIR) and far infrared (IR) spectra. A total of ninety lettuce plants was transplanted for this research, thirty for each experimental crop. The three lettuce crops were grown for thirty days in an aeroponic growth plant chamber inside a greenhouse under favorable conditions. The morphometric and thermal parameters of the lettuce roots (perimeter, area, length and average temperature) and leaves (perimeter, area and average temperature) were evaluated for each crop along ten image-capturing sessions through an implemented multispectral vision system. The average values of the root and leaf morphometric parameters obtained with the implemented imaging system along the lettuce growing period were statistically analyzed with Tukey testing. The obtained analysis results show no significant difference for a value of \(p\leq 0.05\) in 86.67%. Hence, the morphometric parameters can be used to characterize the vegetative lettuce growth in aeroponic crops. On the other hand, a correlation analysis was conducted between the thermal parameters computed with the root and leaf thermal image processing and the measured ambient temperature. The results were: R = 0.945 for correlation between ambient and leaf temperature, R = 0.963 for correlation between ambient and root temperature and R = 0.977 for leaf and root temperature. According to these results, the plant temperature is highly correlated with the ambient temperature in an aeroponic crop. The obtained study results suggest that multispectral image processing is a useful non-invasive tool to estimate the vegetative root and leaf growth parameters of aeroponic lettuce plants in a greenhouse. a 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 2022 202 2022 2022 2022 2022 2022 2 need to consider a variety of resources, ranging from energy efficiency, water saving, to fertilizer use, to provide optimized growth techniques for plants [1]. Today, consumers are increasingly interested in fresh and balanced food, which has caused a great demand for healthy ready-to-eat vegetables. Globally, lettuce is a fresh, high-demand salad vegetable [2]. Due to the high concentrations of vitamins, minerals, dietary fiber and antioxidant compounds, it is considered a health-promoting food [3]. Lettuce has become one of the main types of vegetables for aeroponics in plant production due to its short growing time, short plant shape and market demand [4]. In such circumstances, the aeroponic system is considered a modern and innovative plant cultivation method that is also safe and respectful with the environment due to water saving and low-energy consumption [5]. Aeroponics encourages significant root growth, with a higher root/shoot ratio, as well as significantly greater root length, area, volume and biomass [6; 7]. The root system plays a key role in the plant water and nutrition absorption process [8]; the development of crops having robust roots systems leads to higher crop production in hostile environmental conditions. Consequently, an aeroponic system has significant cultivation advantages over other techniques. Clean products can be harvested sequentially in aeroponics, that is, a new crop can be transplanted immediately after harvest.