Autofluorescence in Plants

Abstract

Plants contain abundant autofluorescent molecules that can be used for biochemical, physiological, or imaging studies. The two most studied molecules are chlorophyll (orange/red fluorescence) and lignin (blue/green fluorescence). Chlorophyll fluorescence is used to measure the physiological state of plants using handheld devices that can measure photosynthesis, linear electron flux, and CO2 assimilation by directly scanning leaves, or by using reconnaissance imaging from a drone, an aircraft or a satellite. Lignin fluorescence can be used in imaging studies of wood for phenotyping of genetic variants in order to evaluate reaction wood formation, assess chemical modification of wood, and study fundamental cell wall properties using Förster Resonant Energy Transfer (FRET) and other methods. Many other fluorescent molecules have been characterized both within the protoplast and as components of cell walls. Such molecules have fluorescence emissions across the visible spectrum and can potentially be differentiated by spectral imaging or by evaluating their response to change in pH (ferulates) or chemicals such as Naturstoff reagent (flavonoids). Induced autofluorescence using glutaraldehyde fixation has been used to enable imaging of proteins/organelles in the cell protoplast and to allow fluorescence imaging of fungal mycelium.

Light and CO2 Modulate the Accumulation and Localization of Phenolic Compounds in Barley Leaves

“…This study further noted that while total phenolic compositions varied, the blue fluorescent signal from cell-wall bound PhCs in the epidermis remained constant (also observed by Lichtenthaler and Schweiger [ 40 ]). The most prevalent cell-wall bound PhCs are hydroxycinnamic acids [ 40 , 60 ] and specifically ferulic acid in Poaceae [ 61 ]. The observed primary presence of PhCs in the mesophyll, rather than in the epidermis, of barley leaves is a relatively unique result which suggests that leaves of different species and phenological stages present varied PhC-modulated leaf protective responses.…”

Current and future advances in fluorescence-based visualization of plant cell wall components and cell wall biosynthetic machineries

“…In photosynthetic cells, chlorophyll is the major source of autofluorescence, joined by the cell wall phenolics and other endogenous fluorophores such as ferulates, flavonoids, etc., recently extensively reviewed by Donaldson [ 84 ]. Figure 3 shows the emission spectra for many of these molecules in Arabidopsis , which falls mainly in the blue-green and red regions of the optical spectra.…”

Biosensors: A Sneak Peek into Plant Cell’s Immunity

“…Besides some general instrumentation constraints, for instance focus drift and unstable laser power in the first couple of hours, uneven illumination and time-consuming high-quality image acquisition [ 134 ], imaging of FPs in plants is affected by fluorescent compounds found in cuticle, cell walls, plastids and vacuoles, such as lignin, chlorophyll and other pigments, etc. [ 135 ]. These components generate high background and cause low SNR in detection of fluorescent reporters.…”