How to Measure Sugar Levels in Plants

Plants grow, regenerate and release oxygen into the atmosphere through the process of photosynthesis. During periods of darkness, plants use glucose or other sugar as a source of energy. Similarly, glucose serves as an important energy source in the human body, which helps cells and organs function properly. However, glucose is just one type of sugar present in plants. Fructose, galactose, melibiose, sucrose and stachyose are other sugars present in various plant extracts. The percentage of sugar in plants indicates not only the amount of protein and mineral present, but also the protein quality. Brix tests -- the unit of measurement used to estimate sugar levels in plants -- can be conducted using a hand-held device called a refractometer.

Distilled water
Brix refractometer

Instructions

- 1
  Collect a plant sample for measurement. Place a leaf in a garlic crusher or similar instrument to extract juice for sampling. Extract enough liquid to produce at least two to three drops for testing.
- 2
  Check to ensure the refractometer’s eyepiece, adjustment screw, mirror tube, cover plate and prism are intact and working properly. Cover the prism with distilled water and shut the cover plate over the prism. Look through the eyepiece, while adjusting the boundary between the light and dark fields until it reaches zero. Since plant extracts are measured according to their refractive index, or the speed that light travels through the sample, the contrast between the light and shadow areas on the prism will indicate the level of sugar in the plant sample. Dry the prism with a soft cloth or fabric before depositing your sample.
- 3
  Deposit two to three drops of the sample liquid onto the glass prism provided. Use the cover plate to spread the sample liquid across the measurement prism. Ensure there are no air bubbles or dry areas that may distort or cause an inaccurate reading. Wait at least 30 seconds before looking through the eyepiece.
- 4
  Focus the eyepiece to collect an accurate reading of the plant’s sugar level. Rotate the eyepiece and adjust the refractometer’s positioning against the light to add more precision during measurement. The location of the shadowline on the printed scale will indicate the sugar concentration in the sample. Check results against the international Brix percentage, which is determined by the International Sugar Analysis Committee.

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