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Measurement of Sucrose Transfer

Sucrose is normally an electrically neutral molecule. But inside the vine, it is combined with a hydrogen ion and moves about as an electrically charged molecule. Movement of "charged sucrose" can be measured electronically. To do this, we measure the electrical potential difference between a sensor in the petiole and a sensor in the berry.

The electrical potential difference is a measure of the strength of the sucrose source in the leaf and the resistance which the sucrose encounters in moving from the leaf to the berry. The graph of the cumulative daily potential difference day by day gives a measure of the magnitude and uniformity of sucrose transfer between leaf and berry from pre-veraison to harvest. For example, if the loading on the shoot is low due to thinning or variety difference, the sucrose transferred to the remaining berries is high and the electrical potential difference is high. If the berry has a low water content, resistance to sucrose movement is high and it takes more force to move the sucrose. This leads to a high electrical potential difference.

Below is a technical abstract supporting this measurement concept.




William G. Gensler, Agricultural Electronics Corporation

Electrically charged sucrose is commonly employed by plants to facilitate movement through cell membranes. This study addresses the question of whether this same mechanism is employed to move sucrose from the leaf to the berry.

Electrochemical sensors were implanted in fifteen petioles and berries in a block of syrah and a block of pinot noir vines in Monterey County, California. Measurements were made every half hour of the electrical potential of the petiole and berry from pre-veraison to harvest as well as cluster count, cluster weight and brix.

Data analysis indicates electrical potential difference between petiole and berry relates to sucrose movement. This relation can be explained with an electro/osmotic model that takes into account the magnitude of the sucrose source, the resistance to transport in the pathway between source and sink and the number of berries on the shoot.

Copies of the complete study are available upon request.

Water Content and Sucrose Transport Scales - Years 2002 to 2005 Growing Seasons

Over the years the Agricultural Electronics Corporation has used the Phytogram to compile and process Petiole and Berry Water Content, and Sucrose Transport Scale statistics. Such measurements were developed 24/7. This has enabled the irrigation manager to review plant-based site status via the Internet. From this experience, the following scales were developed.

  Petiole Water Content Scale 1   Berry Water Content Scale 2   Sucrose Transport Scale3
140 - 90 Vigorous Growth , Shoot Tips Expnding 40-20 Normal Pre Harvest Range 190K-100K High Temp Regions, No Arrests
90-70 Moderate Growth, Shoot Tip Still Expanding 20-16 Moderate Deficit, Near Harvest Range 100K- 60K Medium Temp Regions
Short Term Arrests
70-50 No Growth, Shoot Tip Static 16-12 High Deficit, Harvest Range for
Hiigh Quality Pinot Noir
60K - 30K Marine Influenced Regions,
Long Term Arrests
50-30 Stress Range, No Growth, Shoot Tip Static 12-8 Very High Deficit, Harvest Range for
High Quality Syrah, Dimpling
30K - 7K Very Long Term Arrests,
Low Daily Rate
30-15 High Stress Range 8-0 Raisining    
  1: Units: Nanofarads/millimeter
U.S. Patent 6,870376B1
  2: Units: Nanofarads/millimeter
U.S. Patent 6,870376B1
  3 Units: Millivolts-hours, Patent Pending

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