Indicators of nitrogen status for ornamental woody plants based on optical measurements of leaf epidermal polyphenol and chlorophyll contents

A Review of Methods for Sensing the Nitrogen Status in Plants: Advantages, Disadvantages and Recent Advances

“…Leaf chlorophyll content can be used as a nitrogen status indicator because this is an essential element in photosynthetic protein synthesis [4,11]. The SPAD-502-Soil-Plant Analyses Development chlorophyll meter is one of the most used instruments in plant N determination studies [11,34–36]. A leaf section is enclosed in a small chamber and it is exposed to two light sources: (1) a red- (640 nm) and (2) an infrared light (940 nm) positioned just above the leaf.…”

“…Light filtered through the leaf is captured sequentially by sensors below the leaf. The difference in transmission of the filtered wavelengths is the chlorophyll content indicator per unit leaf area [11]. The Dualex is another device which focuses on measuring polyphenolic compound content in leaves by means of chlorophyll fluorescence.…”

“…The Dualex is another device which focuses on measuring polyphenolic compound content in leaves by means of chlorophyll fluorescence. Essentially water-soluble glycosylated flavonoids, polyphenols are carbon-based compounds and secondary metabolism products in leaves, generated when plants are under N deficiency stress and stored in cell vacuoles [11]. They play an important role in plants as chemical defense against herbivores, as well as protection against UV radiation, free radicals, stress, and pathogens [3].…”

“…Those indices were significantly and exponentially related to leaf N content, and they minimized chlorophyll sensitivity to growth stages and genotypes. In a study focused on leaf N content estimated in ornamental plants, SPAD reading variations due to leaf age can be reduced by choosing the youngest leaves that have already reached 75% of their final growth size [11]. Chlorophyll measurements can be applied in rice under alternate wetting-drying irrigation as well as in continuously flooded fields.…”

“…Several studies have reported on faster and non-destructive new tools designed for plant N status estimation. Optical properties of some leaf pigments, such as chlorophyll and polyphenols, have been used as plant N status indicators [11]. Some of these tools measure leaf chlorophyll content, which is highly correlated to plant N status ( i.e.…”