Food security has been considerable from last several centuries and recently it has become a serious matter of concern because of rapid growth in world population as well as fluctuation in global climate throughout the crop production. Many research groups have been studied to develop food crops deal with climate change.
However, it requires lots of time and effort to obtain expected result because plants growth is highly influenced by a large number of environmental factors which are not easy to maintain at a same time.
Therefore, a fast, accurate and reliable phenotypic technique to analyze the effect of environmental factors on the crop breeding is still required.
This study was conducted to investigate the stress response of red pepper (Hongjinju) and tomato (Super Dotaerang) leaves under water stress. Two hyperspectral imaging techniques, fluorescence (400∼700 nm) and short wave infrared reflectance (SWIR, 1000∼1800 nm), were used to acquire the spectral image for the red pepper and tomato leaves with and without water stress. In this study, red peppers and tomatoes were used and both samples were divided into two groups as normal group and stressed group based on the water supply or not. The normal group was provided with sufficient water every day, while the stressed group was kept away from irrigation throughout the entire experimental period. A total of 24 leaves samples (6 samples from each group) were investigated using fluorescence and SWIR hyperspectral imaging techniques.
The acquired spectral data were analyzed with a multivariate analysis method of ANOVA (analysis of variance). The ANOVA model suggested that 558 nm and 1441 nm wavebands from fluorescence and SWIR data respectively were the most effective to determine the stress responses in the red pepper leaves exposed to the water stress. And 558 nm and 1515 nm wavebands were the most effective for determining the stress responses in the tomato leaves. Optimal fluorescence response of red pepper and tomato leaves is the 558 nm, and this result was caused by the green florescent protein that differed from normal to stressed leaves. Two significant SWIR wavebands at 1441 nm and 1515 nm were observed in near infrared region. The waveband at 1441 nm was closed to the water absorption band, and 1515nm was associated with protein which could be caused by the changes in protein composition depending on the water stress condition. The changes in protein content that differ from normal to stressed leaves can be expected from the results of both fluorescence and SWIR images.
The results show that hyperspectral imaging technique has potential for rapid measurement of water stress responses at red pepper and tomato. Hyperspectral imaging technique can be widely applied to monitoring the stress responses of plant leaves which are an indicator of physiological and biochemical changes and can be implemented to understand the interaction of plant metabolism and crop breeding.