Various types of transport mechanisms are needed to fulfil the mineral requirements of a plant. Why are they not fulfilled by diffusion alone ?

Explanation

Various ions, mineral elements and for transport of organic substances, there are various methods in plants, like.
(i) The food prepared by leaves is transported towards root and stem in lower direction.
(ii) The food is transported towards developing leaves, buds and fruits.
(iii) In stem, food is transported towards pulp, cortex and epidermis cross sectionally.
(iv) Ions and mineral elements are transported upwards through xylem.
Diffusion is a slow process and responsible for small distance transport of ions. It can not transport above mentioned organic and inorganic materials. So specific method is necessary for transport of substances till long distance. e.g. Mass flow.