Diagnosis of nitrogen status in Chinese cabbage (Brassica rapa chinensis) using the ratio of amide II to amide I in leaves based on mid‐infrared photoacoustic spectroscopy

Abstract

In order to quickly diagnose the nitrogen status of Chinese cabbage (Brassica rapa chinensis), Fourier transform mid-infrared photoacoustic spectroscopy, a nondestructive and rapid approach was used. Two clear stable peaks, in the range 1680-1650 cm -1 associated with amide I and in the range of 1530-1520 cm -1 associated with amide II, were observed and responded positively to nitrogen treatments. The characteristic bands of amide I and amide II were also accurately separated by curve-fitting via deconvolution using a Gauss expansion function. The ratio of the photoacoustic intensities of amide II to amide I was used for correlation analysis with nitrogen treatment, and the correlation coefficients (R 2 , n = 59) at seedling and growth stage were 0.9769 (P 5%) and 0.9884 (P 5%), respectively. The ratio of the amide II and amide I peaks was found to be an indicator of nitrogen input during the seedling stage such that a ratio of less than 0.9 indicated a low nitrogen input, a ratio between 0.9 and 1.0 indicated a moderate nitrogen input, and a ratio of more than 1.0 implied an excessive N input.

Rapid diagnosis of nitrogen status in rice based on Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS)

“…In the spectrum, the intensity of spectral absorption was usually interfered by the instrument and external environment [18]. Therefore, the ratio of photoacoustic intensity of amide II to amide I in rice leaves was recorded to avoid this interference (Fig.…”

“…An appropriate amount of ground samples was placed in the photoacoustic cup for direct determination in the infrared photoacoustic spectrum. Before the determination was made, helium was purged for 20 s to reduce the infrared absorption interference from carbon dioxide and water in the air [18]. Scans were conducted in the wavenumber range of 4000 to 500 cm −1 , the mirror speed was set to 0.32 cm s −1 , and the resolution was 4 cm −1 .…”

“…Nowadays, as a promising alternative, Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) has been effectively applied in many fields, such as analyzing soil physical and chemical properties [12, 13], identification of plant diseases [14], gas monitoring [15], and food safety [16, 17]. Compared to the near-infrared spectrum, the mid-infrared spectrum provides more information about the measured targets [18–20]. From the scattering of plant tissue [21], photoacoustic spectroscopy can capture more information from leaves due to the depth-profiling abilities, and then assess the nutritional status of plants tissue [18].…”

“…Compared to the near-infrared spectrum, the mid-infrared spectrum provides more information about the measured targets [18–20]. From the scattering of plant tissue [21], photoacoustic spectroscopy can capture more information from leaves due to the depth-profiling abilities, and then assess the nutritional status of plants tissue [18]. However, the scope of infrared photoacoustic spectroscopy to assess nitrogen nutrition levels in rice production remains unexplored.…”

VISIBE AND INFRARED SPECTRAL CHARACTERISATION OF CHINESE CABBAGE (BRASSICA RAPA L. SUBSPECIES CHINENSIS), GROWN UNDER DIFFERENT NITROGEN, POTASSIUM AND PHOSPHORUS CONCENTRATIONS

“…Limited research has been conducted on Chinese cabbage characteristics -structure (van Averbeke et al, 2007), growth period and environmental conditions (Kalisz, 2011) as well as optimal fertiliser inputs for maximum yields (Ahmad et al, 2014;Li et al, 2015). Thus, there is limited-to-nil research conducted to analyse the spectral properties of Chinese cabbage relative to various fertiliser treatments.…”