Experimental Techniques for Measuring Transport

More specialized systems of study involve the collection of xylem or phloem sap. Xylem sap can be collected from the stems or leaf bases of many plants, though care must be taken to avoid contamination with cell contents and phloem sap. Hsu et alP recently developed a sophisticated technique in which chemicals were applied to nutrient solutions bathing roots of soybean Glycine max) and application of pressure to the root chamber gave realistic rates of xylem sap flow from the stem stump. Phloem sap can only be readily collected from a few plant species, with the techniques most used in pesticide research involving excised leaves of legumes, excised flowering stems of yucca. or incisions made in the stem of castor bean Ricinus communis) plants.  

The use of different experimental systems and the lack of adequate detail in many articles concerning translocation make comparisons difficult a more consistent approach would be very helpful. While such consistency is less easy to achieve in the case of phloem translocation, results from studies on uptake and translocation following application to roots via nutrient solution can readily be presented in a standard way (see Sections 9.S.2.2 and 9.3.2.3). 

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