We've just incorporated a phloem carbohydrate-analysis unit to our
introductory biology sequence. Students cut off six-week cucurbit
leaves, collect the exudate into micro-capillary tubes, and use
anthrone reagent to test for total carbohydrates, comparing against
sucrose standards using Sequoia-Turner spectrophotometers. It worked
(although only after we changed from water to 60% ethanol for
diluting our exudate and making our standards), but the students had
great difficulty getting enough exudate. Does anyone know tricks for
increasing the amount of exudate? Are there particular species or
varieties that work better than others? Tricks about light/dark
cycles or time of day or watering regimes or something?
William E. Williams WEWilliams at smcm.edu
Saint Mary's College of Maryland
18952 E. Fisher Rd.
Saint Mary's City, MD 20686-3001