Plants 2018, 7(1), 10; https://doi.org/10.3390/plants7010010
Imaging and Spectroscopy of Natural Fluorophores in Pine Needles
Lloyd Donaldson 1,*
and Nari Williams 2
and Nari Williams 21
Biotransformation, Scion, Private Bag 3020, Rotorua 3010, New Zealand
2
Forest Protection, Scion, Private Bag 3020, Rotorua 3010, New Zealand
*
Author to whom correspondence should be addressed.
Received: 10 January 2018 / Revised: 24 January 2018 / Accepted: 29 January 2018 / Published: 2 February 2018
(This article belongs to the Special Issue Selected Papers from the 1st International Plant Spectroscopy Conference)
Abstract
Many plant tissues fluoresce due to the natural fluorophores present in cell walls or within the cell protoplast or lumen. While lignin and chlorophyll are well-known fluorophores, other components are less well characterized. Confocal fluorescence microscopy of fresh or fixed vibratome-cut sections of radiata pine needles revealed the presence of suberin, lignin, ferulate, and flavonoids associated with cell walls as well as several different extractive components and chlorophyll within tissues. Comparison of needles in different physiological states demonstrated the loss of chlorophyll in both chlorotic and necrotic needles. Necrotic needles showed a dramatic change in the fluorescence of extractives within mesophyll cells from ultraviolet (UV) excited weak blue fluorescence to blue excited strong green fluorescence associated with tissue browning. Comparisons were made among fluorophores in terms of optimal excitation, relative brightness compared to lignin, and the effect of pH of mounting medium. Fluorophores in cell walls and extractives in lumens were associated with blue or green emission, compared to the red emission of chlorophyll. Autofluorescence is, therefore, a useful method for comparing the histology of healthy and diseased needles without the need for multiple staining techniques, potentially aiding visual screening of host resistance and disease progression in needle tissue. View Full-TextKeywords:
autofluorescence; lignin; suberin; ferulate; flavonoid; terpene; chlorophyll; pine needle; spectroscopy
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Donaldson, L.; Williams, N. Imaging and Spectroscopy of Natural Fluorophores in Pine Needles. Plants 2018, 7, 10.
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