`star` Long Distance Transport of Water
`star` Water Absorption from soil to Root hair


● `color{violet}("Long distance transport")` of substances within a plant cannot be by `color{brown}("diffusion alone.")`

● `color{violet}("Diffusion")` is a slow process.

● It can account for only `color{brown}("short distance")` `color{violet}("movement of molecules") `.

● For example, the `color{violet}("movement of a molecule")` across a typical plant cell (`color{brown}("about 50 μm")` ) takes approximately `color{brown}("2.5 s.")`

● In large and `color{violet}("complex organisms,")` often substances have to be moved across very `color{violet}("large distances.")`

● Sometimes the `color{violet}("sites of production or absorption")` and sites of storage are too far from each other; diffusion or
active transport would not suffice.

● Special `color{brown}("long distance transport systems")` become necessary so as to move substances across long distances and at a `color{violet}("much faster rate.")`

● `color{violet}("Water and minerals, and food")` are generally moved by a `color{brown}("mass")` or `color{brown}("bulk flow system.")`

● `color{violet}("Mass flow")` is the movement of substances `color{brown}("in bulk or 𝑒𝑛 𝑚𝑎𝑠𝑠𝑒")` from one point to another as a result of pressure differences between the two points.

● It is a characteristic of `color{violet}("mass flow")` that substances, whether in solution or in suspension, are swept along at the
same pace, as in a `color{violet}("flowing river.")`

● This is `color{violet}("unlike diffusion")` where different substances move independently depending on their concentration gradients.

● `color{violet}("Bulk flow")` can be achieved either through a `color{brown}("positive hydrostatic pressure")` gradient (e.g., a garden hose) or a `color{brown}("negative hydrostatic pressure")` gradient (e.g., suction through a straw).

● The `color{violet}("bulk movement")` of substances through the conducting or vascular tissues of plants is called `color{brown}("translocation")`.

● The `color{violet}("higher plants")` have highly specialised vascular tissues – `color{brown}("xylem and phloem.")`

● `color{brown}("Xylem")` is associated with translocation of mainly `color{violet}("water, mineral salts, some organic nitrogen and hormones")` , from roots to the aerial parts of the plants.

● The `color{brown}("phloem")` translocates a variety of `color{violet}("organic and inorganic")` solutes, mainly from the leaves to other `color{violet}("parts of the plants.")`


● We know that the `color{brown}("roots absorb")` most of the water that goes into `color{violet}("plants")` ; obviously that is why we apply water to the `color{violet}("soil")` and not on the `color{violet}("leaves.")`

● The responsibility of `color{violet}("absorption of water and minerals")` is more specifically the function of the `color{violet}("root hairs ")` that are present in millions at the tips of the `color{violet}("roots.")`

● `color{violet}("Root hairs")` are thin-walled slender extensions of `color{brown}("root epidermal cells")` that greatly increase the surface area for `color{violet}("absorption.")`

● Water is absorbed along with `color{violet}("mineral solutes")`, by the `color{violet}("root hairs,")` purely by `color{brown}("diffusion.")`

● Once water is absorbed by the `color{violet}("root hairs,")` it can move deeper into `color{violet}("root layers ")` by two distinct pathways:

`color{green}(star \ \ " Apoplast pathway")`

`color{green}(star \ \ "Symplast pathway")`