Xyleemsap

Xyleemsap is a coined term in plant physiology referring to the dissolved phase transported within the xylem of vascular plants. It denotes the aqueous solution that carries water, inorganic nutrients, organic solutes, and signaling molecules from roots to aerial tissues. The term emphasizes the functional role of xylem sap as a conduit for both nutrition and communication within the plant.

Typical constituents include water, inorganic ions (such as nitrate, potassium, calcium, and magnesium), sugars (notably sucrose), amino acids, organic acids, vitamins, and hormones including abscisic acid, cytokinins, and jasmonates; trace volatiles and peptides are also reported.

Xyleemsap flow is driven by transpiration pull and root pressure; its composition changes with soil moisture, temperature, developmental stage, and stress conditions. Under drought, ABA and other signaling molecules may become enriched.

Methods to study Xyleemsap include exudation from cut stems or collection with pressure chambers; sample purity is a concern due to contamination with phloem sap or apoplastic fluids; standardization is ongoing.

Applications of the concept include diagnosing nutrient status, understanding long-distance signaling, and guiding strategies to improve crop resilience.

Name origin: blends 'xylem' and 'sap'. Some authors use Xyleemsap as a general term for the xylem sap fraction, while others reserve it for a proposed functional subset enriched in signals.

Related topics include Xylem, xylem sap, and plant signaling.