Figure 1. Nitrate circulation via phloem sap : (a-f) Typical
species where phloem nitrate has been directly measured or inferred from
isotopic mass-balance: palm trees (a), cereals (wheat and rice) (b),
Western candle tree Banksia prionotes (c), castor bean (d),
sunflower (e), and Arabidopsis (f). (g) Summary of hypothetical roles of
nitrate circulation via phloem sap (see text for further details).