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phloem bundle. Vascular phloem bundle.

Vascular phloem bundle is a part of the transport system in vascular plants. 

The transport itself happens in Vascular phloem bundle tissue.

Vascular phloem bundle exists in two forms: 

Vascular phloem bundle xylem and 

Vascular phloem bundle phloem. 

Both these tissues are present in a Vascular phloem bundle.

Vascular phloem bundle include supporting and protective tissues. 

Also, it is a vein in the leaf that contains Vascular phloem bundle conducting tissues.

The xylem of Vascular phloem bundle typically lies adaxial with phloem positioned abaxial. 

In a stem or root this means that the Vascular phloem bundle xylem is closer to the centre of the stem 

or root while the Vascular phloem bundle phloem is closer to the exterior. 

In a leaf, the Vascular phloem bundle adaxial surface of the leaf will usually be the upper side, 

with the Vascular phloem bundle abaxial surface the lower side. 

This is why Vascular phloem bundle aphids are typically found on the underside of a leaf rather than on the top, 

since the sugars manufactured by the plant are transported by the Vascular phloem bundle , which is closer to the lower surface.

The position of Vascular phloem bundle relative to each other may vary considerably.

Vascular phloem bundle sheath cells are contained in certain C4 plants. 

These Vascular phloem bundle plants use C4 carbon fixation to carry out photosynthesis when 

normal conditions for C3 plants aren't present e.g. normal water levels, 

CO2 levels, heat, light.

Vascular phloem bundle sheath cells are photosynthetic cells arranged into tightly packed 

sheaths around the veins of a leaf. 

Vascular phloem bundle form a protective covering these leaf veins, and consist of one or more cell layers, 

usually parenchyma. 

Between the Vascular phloem bundle sheath and the leaf surface are the more loosely arranged mesophyll cells. 

The Calvin cycle is confined to the chloroplasts of these Vascular phloem bundle sheath cells.