Phloem – Transportation of Minerals (i.e sugars)

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transport in phloemphloem cells must be living for transport to occur. Materials can move through phloem in more than one direction in the same time. Phloem transport large amounts of material quite rapidly within the plant. Oxygen deficiency & low temps. inhibit but do not stop phloem transport. Characteristics of movement of particular substance vary from one plant to another
Mas / Pressure Flow Theory (sugar)relies on combination of osmosis & pressure dynamics. transportation of sugar. Sugar is actively pumped into the phloem.

A high concentration of organic substance inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient (osmotic gradient) that draws water into the cells. Movement occurs by bulk flow (mass flow); phloem sap moves from sugar sources to sugar sinks by means of turgor pressure, also known as hydrostatic pressure. A sugar source is any part of the plant that is producing or releasing sugar. During the plants growth period, usually during the spring, storage organs such as the roots are sugar sources, and the plants many growing areas are sugar sinks.

sink – where sugar is transported to and then off loaded to where
there is a collection of sugar after photosynthesis

source – where materials are loaded into from phloem

b/c the phloem will be hypertonic to its surrounding, water goes into the phloem and the increase in pressure makes the water and sugar move up the platn.

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