From Simple English Wikipedia, the free encyclopedia
In
vascular plants
,
phloem
is the living
tissue
made up of small tubes which carry watery
sap
containing
sugar
and other
organic
nutrients
to all parts of the plant where the nutrients are used for growth, or stored until needed. The sugar is made by
photosynthesis
. In
trees
, the phloem is the innermost layer of the
bark
, therefore the name, that comes from the
Greek
word φλοιο? (
phloios
) for "bark".
Aphids
(greenfly) and other
insects
feed on the phloem by inserting a fine tube into the plant, penetrating the tiny phloem cells deep within the plant. The high pressure in the phloem tubes forces the phloem sap into the insect. Most of the sugar passes right through the insect, so that nearby surfaces get sticky and often become black due to the growth of
fungus
.
Water, which is absorbed by the plant's
roots
, travels up the stem to the leaf through the
xylem
. This means that the xylem helps during
photosynthesis
by bringing water up the plant. It does the same job that
blood vessel
s do in animals.