In vivo diagnostics of early abiotic plant stress response via Raman spectroscopy

Abstract

Development of a phenotyping platform capable of noninvasive biochemical sensing could offer researchers, breeders, and producers a tool for precise response detection. In particular, the ability to measure plant stress in vivo responses is becoming increasingly important. In this work, a Raman spectroscopic technique is developed for high-throughput stress phenotyping of plants. We show the early (within 48 h) in vivo detection of plant stress responses. Coleus (Plectranthus scutellarioides) plants were subjected to four common abiotic stress conditions individually: high soil salinity, drought, chilling exposure, and light saturation. Plants were examined poststress induction in vivo, and changes in the concentration levels of the reactive oxygen-scavenging pigments were observed by Raman microscopic and remote spectroscopic systems. The molecular concentration changes were further validated by commonly accepted chemical extraction (destructive) methods. Raman spectroscopy also allows simultaneous interrogation of various pigments in plants. For example, we found a unique negative correlation in concentration levels of anthocyanins and carotenoids, which clearly indicates that plant stress response is fine-tuned to protect against stress-induced damages. This precision spectroscopic technique holds promise for the future development of high-throughput screening for plant phenotyping and the quantification of biologically or commercially relevant molecules, such as antioxidants and pigments.Raman spectroscopy | plant abiotic stress | carotenoids | anthocyanins W ith the global population projected to exceed 9 billion by the year 2050, the task of producing enough food and energy for the world is of utmost importance (1). In anticipation of rising food demand (2), the ability to measure plant stress in vivo is becoming increasingly vital for increasing agricultural production and research. For example, such technologies would allow a farmer to intervene on stress detection and also, make practical the development of crop varieties with increased tolerance to abiotic stress. The field environment requires a comprehensive and rapid screening technology for plant physiological, biochemical, and morphological characteristics (3). Such characteristics can be integrated to predict plant growth potential, biomass processibility, and abiotic stress responses before any visible signs occur in a plant. Plant growth is impacted by unseasonable droughts, cold, increased UV radiation and high-energy blue light associated with atmospheric changes in ozone levels, and fertilizer/irrigation application associated with increased soil salinity (4, 5). Most existing methods for evaluating biochemical characteristics use destructive chemical analyses, which require time and intensive labor. In addition, these methods use strong chemicals, which require special handling and disposal. Currently, in vivo sensing technologies are limited by the time required for detecting a stress response, the types of stress factors that can be detec...

Reply to Dong and Zhao: Plant stress via Raman spectroscopy

“…Dong and Zhao (1) attempt to provide perspective on our use of Raman spectroscopy in plant stress studies (2). Unfortunately, their experimental criticism is incorrect and their technical suggestions won't work.…”

“…Dong and Zhao (1) do not understand our experiment. The Raman peak at 1,525 cm −1 is strong, but cannot be used for our purposes involving simultaneous detection of two molecules (2). We cannot use these peaks because anthocyanin's 1,516-1,545 cm −1 peaks overlap with carotenoids' 1,525 cm −1 .…”

Time‐resolved assessment of drying plants by Brillouin and Raman spectroscopies

“…Brillouin spectra are collected using a tandem Fabry–Perot interferometer coupled with a photomultiplier. Abbreviations: BS, beam splitter; FP1, Fabry–Perot etalon 1; FP2, Fabry–Perot etalon 2; L, lens; M, mirror; PMT, photomultiplier tube; PR, prism [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…However, to the best of our knowledge, dynamic changes of Raman spectra (and, subsequently, chemical and/or structural composition) of plants or leaves upon drying have never been reported. The only one exception was a publication of Altangerer et al about changes in Raman spectra in limited ranges (500–800 and 950–1,250 cm −1 ) for the observed in vivo Coleus plant under four types of abiotic stress conditions, including drought stress, when “normal watering was withheld.” However, the changes in plant mass due to desiccation or water mass loss (%) as well as changes in Raman peak area ratios were not quantified and reported in this study.…”

Physiological and Morphological Responses to Ozone Exposure of Coleus (Solenostemon scutellarioides (L.) Codd)

“…The changes in leaf color may be due to the plant producing more anthocyanin [25]. Notable increase and decrease regarding anthocyanin and carotenoid after environmental stress in which concentration levels of anthocyanins and carotenoids change in an opposite pattern, which points toward the response of this plant under environmental stress is improved to defend the plants against changes that induce damages [26].…”