The anionic composition was determined for pure rice phloem sap which had been collected from brown planthopper stylets by cutting them with a YAG laser beam. The most abundant inorganic anion was Cl− at 52.1 mM. PO43− and SO42− were found at 8.1 mM and 1.8 mM, respectively. NO3− was present at 1.9 mM when the rice had been grown with nutrient solution containing 0.35 m of NO3− The phloem sap also contained malic, succinic and citric acid at 7.3, 3.0 and 3.2 mM respectively. Small amounts of other organic acids were also found.
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Hayashi et al. (1985) studied this question.