LONG DISTANCE TRANSPORT OF WATER
● `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.")`
● `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.")`
