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

Explanation

Various types of ions, minerals and organic compound are transported in plants in various modes, e.g.,
(i) Food substances synthesised in leaves are translocated downward towards root and stem.
(ii) Similarly food is translocated upwards to the developing leaves, buds and fruits.
(iii) Radial transport of food occurs across the stem from the cells of pith, from cortex act, towards epidermis.
(iv) Ions and minerals are transported upwards through xylem.
Since, diffusion is a slow process and allows movement of molecules for short distances only, it cannot filled and alone carry out the above mentioned movements of organic and inorganic substances. therefore, a need arises for special long distance transport systems that permits and move substances at a much faster rate, i.e., mass or bulk flow system through conducting tissues (translocation).