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New Raman sensor for precision agriculture
Stressed basil plant

Sometimes stress can just creep up on you. Lack of sleep, lack of nutritious food and not drinking enough water have a cumulative effect. Yes, it’s a tough life being a basil plant. Happily precision agriculture techniques can now give early indication that crops are getting stressed. A new portable Raman sensor may help farmers to spot when plants need additional care and attention.

Researchers from the Disruptive & Sustainable Technologies for Agricultural Precision group, part of the Singapore-MIT Alliance for Research and Technology, recently reported an intriguing new method to measure plant nutrients non-invasively. Working at the Temasek Life Science Laboratory in Singapore in collaboration with colleagues at MIT in Massachusetts, they developed and tested a handheld Raman spectroscopy probe for plants. Their innovation was capable of measuring phytonutrients such as beta-carotene and lycopene and nitrate ions (a macronutrient).

Raman spectroscopy is a chemical analysis technique that produces a kind of fingerprint of the vibrations of molecules. Laser light of a single colour is focused onto the sample of interest and light scattered by the sample is collected with a lens or mirror. Virtually all of the light is scattered with the same energy as the laser but something like 1 in a billion of the laser photons is scattered with less energy. The energy difference between the laser and the scattered light corresponds to the energy of a vibration of the molecule. Heavy molecules vibrate slowly, light ones more quickly and large molecules have many different vibrations while simple molecules like oxygen O2 have just one. When the scattered light is dispersed by a prism or grating, the scattered light is separated into a spectrum. Different vibrations of molecules can be identified by the ‘fingerprint’ spots of light in the spectrum.

Raman spectra of five plant leaves, simple nitrate nutrients and four carotenoid phytonutrients (courtesy Nature Scientific Reports)

As the figure above shows, small nitrate molecules have simple spectra with few vibrations but bigger molecules like the carotenoids lycopene, neoxanthin and beta-carotene have many more vibrational Raman peaks. The Singapore-MIT team recorded Raman spectra from the leaves of six different leaf vegetables: arabidopsis, spinach, Pak Choi, Choy Sum, lettuce and Kailan. The spectra of the leafy vegetables look very similar because the leaves are made from similar components (typically lignin, cellulose, pectin and carotenoid) giving the plant cell walls structure and internal colour.

Raman plant probe comprising: an optical fibre probe for laser excitation and Raman collection and magnetic leaf holder (courtesy Nature Scientific Reports)

Surprisingly, the probe was sufficiently sensitive to detect nitrate ions in the water in the leaves. Using a prototype Raman leaf probe, the team compared hydroponic plant growth with sufficient nitrate and with insufficient nitrate. Signal levels were not as good as those of a laboratory Raman instrument but taking a ratio of the 1046 cm-1 nitrate peak and a nearby 1067 cm-1 peak as a comparison, consistently lower ratios of nitrate were seen in the stressed, nitrogen deficient plants. The figure below compares nitrate starved arabidopsis plants with unstressed controls.

Clear differentiation between nitrate starved arabidopsis plants (-N) and control plants (+N) (courtesy Nature Scientific Reports)

Using a different salad plant, Choy Sum, the handheld Raman probe was able to categorise temperature and drought stress. This time a more sophisticated chemometric technique was used to reveal differences between the three groups of plants.

Raman probe measurement of stressed Choy Sum and control plants, showing small but clear spectral differences (courtesy Nature Scientific Reports)

The photographs show that the plants are starting to wilt due to the lack of water and raised temperature. Less obviously, principal component analysis (PCA) of the Raman spectra was able to categorise the plants into three clusters corresponding to control, drought stressed and temperature stressed conditions.

Chemometric classification of stressed Choy Sum plants (courtesy Nature Scientific Reports)

The Singapore-MIT team have reported a fascinating new method of detecting stress in a number of salad crop plants. They developed an innovative Raman leaf probe instrument and combined with detailed analysis of the spectral data, have an encouraging proof of principle. Further development is required to demonstrate earlier detection of crop stress. Basil plants can look forward to a more relaxed, less stressed future.

Read the recent Nature Scientific Report here. The Singapore-MIT have published additional work on measuring N, P, K nutrients in plants and a convincing genotype study of nitrate uptake in Arabidopsis.


Climate change: a challenge or an opportunity for viticulture?
Vineyards in Adelaide, Australia

October is the time most vineyards have completed the harvest and wineries start the winemaking process. Some wineries are counting a better than ever harvest but others are just counting the cost. This summer the fields of Australia, California, South Africa, Portugal and even Oregon have been ravaged by fire and drought. This year the fields of the United Kingdom and even southern Sweden have been blessed by a long hot summer and exciting prospects for this year’s vintage.

Can innovation offer viticulture a solution to the challenges of climate change? Can innovation realise the opportunities created by climate change?

Three years ago the European Union commissioned the Clim4Vitis project, aiming to mitigate the effects of climate change on European Viticulture. Since its inception the original five member consortium has grown to 200 worldwide members and resulted in the Porto Protocol: Climate Talks.

European Union project 810176 Clim4Vitis

Despite COVID-19, the innovation phenomenon that is Zoom permitted open international discussion of water shortage, pests and diseases, and increased weather variability. During one recent virtual workshop we discovered climate change in Argentina is being mitigated by moving cultivation to higher elevations. Problems and solutions are being shared through on-line networking. Collaborations have been established between local vineyards in Argentina and viticulturalists from Chateau Lafite estates in France. Nobody has all the answers but it seems it’s good to talk!

In Portugal, the FREND project has developed an innovative technology platform for precision viticulture. Precision Agriculture (PA) has been growing in importance for the cultivation of many crops. Through the use of plant characterisation and artificial intelligence, PA offers accurate and timely delivery of water, nutrients and chemical interventions when needed.

According to Antonio Cardoso, CEO of XpectralTEK (FREND project coordinator), their precision viticulture platform has measurable benefits.

In vineyards around Braga we have seen a 20% reduction in the use of water, a 60% reduction in the incidence of disease and a 2% increase in potential grape alcohol as a result of using the FREND viticulture platform.

Antonio Cardoso CEO XpectralTEK

Climate change is posing problems but agricultural innovation is providing solutions. For many climate challenges there are innovative opportunities.

In the UK, vineyard managers have seen many positive opportunities due to climate change. Historically, England was not viewed as a place to produce quality wine. In part this was due to cultivation of grape varieties that would withstand the vagaries of the UK weather. Nobody in southern Europe would choose to grow grape varieties like Bacchus or Reichensteiner. Today however English and Welsh vineyards are growing champagne grapes pinot noir, chardonnay and meunier.

Still and sparkling white wines of outstanding quality are now produced in England. Two Best in Show Decanter World Wine Awards were given to Roebuck Estates and Simpsons Wine Estate this year (2020).

Thanks to expert viticulture and a warming climate, even red wine can be successfully made in England. Lyme Bay Winery in Devon reported a record 14.7% potential alcohol in pinot noir grapes from the 2020 harvest. Greater day length in the North combined with hotter, extended growing seasons now offer a real opportunity for expert wine producers in the South to expand north.

Global climate change will continue to cause chaos and bring challenges to the world of wine. It also brings powerful global reasons to exchange experience and opportunities to innovate solutions. And continue to make excellent wine.