• The xylem tissue forms a continuous column with no end walls which can disturb water flow
• The xylem tissue is made up of long hallow cell which are join end to end that facilitate water flow
• The walls are impregnated with lignin which prevents  the escape of water except where there are pits
• The lignin help to offer supports and prevent under tension which can be created by transpiration pull…

A.PHLOEM

The primary phloem develops from the procabium while secondary phloem develops form the vascular cambium

• The phloem vessel is made up of the following cells: companion cells, sieve tube elements, parenchyma and sclerenchyma (fibre and sclereids)

​​​​​​​a.Companion cells

There are attached to the sieve tube and connected by pits or plasmodesmata. They contain a prominent nucleus and dense active protoplasm which is full of organelles which carry out metabolic activities. They also take part in translocation since their cells have out growths that increase the surface area of the plasma membrane of uptake of substances. As the phloem grows older it sieve tube and companion cell die. There are 3 types of companion cells: ordinary companion, transfer cells and intermediary cells

b.Parenchyma phloem

They contain starch and ternis that offer strength to the phloem

c.Sclerenchyma phloem

As the sclerens grow older they lost their protoplasm and offer rigidity to the plant

d.Sieve tube

• They lack the nucleus and contain sieve plates which allows the flow of soluable substances from cell to cell
• Their cells are placed end to end to form a long sieve tube as the walls a perforated to form sieve plates
• They have large vascules with surrounding cytoplasmic strands which helps in the translocation of food to various parts of the plants

NB: the main function of the phloem is for translocation of soluable organic substance from the leafs to other parts of the plants.