Sap Sap Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from latex, resin, or cell sap; it is a separate substance, separately produced, and with different components and functions. Saps may be broadly divided into two types: xylem sap and phloem sap. Xylem sap (pronounced ) consists primarily of a watery solution of hormones, mineral elements and other nutrients. Transport of sap in xylem is characterized by movement from the roots toward the leaves. Over the past
Black bean aphid by the aphid to improve the flow of sap. To obtain enough protein, aphids need to suck large volumes of sap. The excess sugary fluid, honeydew, is secreted by the aphids. It adheres to plants, where it promotes growth of sooty molds. These are unsightly, reduce the surface area of the plant available for photosynthesis and may reduce the value of the crop. These aphids are also the vectors of about 30 plant viruses, mostly of the nonpersistent variety. The aphids may not be the original source of infection, but are instrumental in spreading the virus through the crop. Various