Sap

Xylem sap (pronounced /ˈzaɪləm/) consists primarily of a watery solution of hormones, mineral elements and other nutrients.

According to Annual Review of Plant Biology,Loading and unloading patterns are largely determined by the conductivity and number of plasmodesmata and the position-dependent function of solute-specific, plasma membrane transport proteins.

Recent evidence indicates that mobile proteins and RNA are part of the plant's long-distance communication signaling system.

[6]Many insects of the order Hemiptera (the half-wings), feed directly on phloem sap, and make it the primary component of their diet.

Phloem sap is "nutrient-rich compared with many other plant products and generally lacking in toxins and feeding deterrents, [yet] it is consumed as the dominant or sole diet by a very restricted range of animals".

These include the existence of a very high ratio of non-essential/essential amino acids in phloem sap for which these adapted Hemiptera insects contain symbiotic microorganisms which can then provide them with essential amino acids; and also insect "tolerance of the very high sugar content and osmotic pressure of phloem sap is promoted by their possession in the gut of sucrase-transglucosidase activity, which transforms excess ingested sugar into long-chain oligosaccharides.