Analysis of Chlorophyll Concentration in Potato Crop by Coupling Continuous Wavelet Transform and Spectral Variable Optimization

The analysis of chlorophyll concentration based on spectroscopy has great importance for monitoring the growth state and guiding the precision nitrogen management of potato crops in the field. A suitable data processing and modeling method could improve the stability and accuracy of chlorophyll analysis. To develop such a method, we collected the modelling data by conducting field experiments at the tillering, tuber-formation, tuber-bulking, and tuber-maturity stages in 2018. A chlorophyll analysis model was established using the partial least-square (PLS) algorithm based on original reflectance, standard normal variate reflectance, and wavelet features (WFs) under different decomposition scales (21–210, Scales 1–10), which were optimized by the competitive adaptive reweighted sampling (CARS) algorithm. The performances of various models were compared. The WFs under Scale 3 had the strongest correlation with chlorophyll concentration with a correlation coefficient of −0.82. In the model calibration process, the optimal model was the Scale3-CARS-PLS, which was established based on the sensitive WFs under Scale 3 selected by CARS, with the largest coefficient of determination of calibration set (Rc2) of 0.93 and the smallest Rc2−Rcv2 value of 0.14. In the model validation process, the Scale3-CARS-PLS model had the largest coefficient of determination of validation set (Rv2) of 0.85 and the smallest root–mean–square error of cross-validation (RMSEV) value of 2.77 mg/L, demonstrating good prediction capability of chlorophyll concentration. Finally, the analysis performance of the Scale3-CARS-PLS model was measured using the testing data collected in 2020; the R2 and RMSE values were 0.69 and 3.36 mg/L, showing excellent applicability. Therefore, the Scale3-CARS-PLS model could be used to analyze chlorophyll concentration. This study indicated the best decomposition scale of continuous wavelet transform and provided an important support method for chlorophyll analysis in the potato crops.

Analisis Kandungan Klorofil Pada Beberapa Posisi Anak Daun Aren (Arenga pinnata) dengan Spektrofotometer UV-Vis

Tanaman aren merupakan salah satu tanaman penghasil gula bagi kehidupan manusia. Tanaman ini merupakan tanaman penghasil gula tertinggi daripada tanaman tebu dan tanaman bit. Kemampuan tanaman aren dalam memproduksi gula sangat berhubungan dengan kandungan klorofil pada bagian daun. Penelitian ini dilakukan untuk mengembangkan metode analisis klorofil pada daun dan menentukan posisi anak daun yang memiliki kandungan klorofil tertinggi. Analisis kandungan klorofil dilakukan dengan metode ektraksi pelarut yang absorbansinya dibaca pada spektrofotometer UV-Vis. Kandungan klorofil a yang terdapat pada daun aren bervariasi, yaitu berkisar 22 - 39 µg/mL ; 1,5 - 2,3 mg/g ; 633 - 1.000 µmol /m 2 sedangkan untuk klorofil b yang terdapat pada daun aren bervariasi sekitar 6 - 10 µg/mL ; 0,4 - 0,7mg/g ;170 - 293 µmol/m 2.Posisi anak daun pada daun memiliki kandunngan klorofil yang lebih tinggi pada bagian atas, sedangkan yang terendah pada bagian bawah. Pada posisi kiri pada daun aren,kandungan klorofilnya lebih tinggi dibandingkan pada posisi kanan,sedangkan posisi pangkal, tengah, dan ujung pada anak daun hampir sama kandungan klorofilnya.Sugar palm is one of the sugar-producing plants for human life. This plant can produce sugar higher than a sugar-producing plant with sugar cane and beet plant. The ability of sugar palm in producing sugar is related to chlorophyll content in the leaf. This research was conducted to develop the method of chlorophyll analysis in the leaf and determine the position of leaflet that have the highest chlorophyll content. Analysis of chlorophyll content was performed by solvent extraction method that absorbance was read on UV-Vis spectrophotometer. The content of chlorophyll present in palm leaves varies, ranging from 22 - 39 μg /mL; 1.5- 2.3 mg/g or 633- 1,000 μmol/m2 whereas for chlorophyll b present in sugar palm varies from about 6 - 10 μg/mL; 0.4 -0.7 mg/g or 170 - 293 μmol/m2. The leaflet position on the leaves has a higher chlorophyll content at the top, while the lowest is at the bottom. In the left position on the palm leaves, chlorophyll content is higher than the right position, while the position of base,middle,and end of the leaflet leaves almost the same content.