● After the `color{violet}("ions")` have reached xylem through `color{brown}("active or passive uptake,")` or a combination of the two, their further transport up the stem to all parts of the plant is through the `color{brown}("transpiration stream.")`
● The `color{brown}("chief sinks")` for the mineral elements are the growing regions of the `color{violet}("plant")`, such as the apical and lateral meristems, young leaves, developing flowers, fruits and seeds, and the `color{violet}("storage organs.")`
● `color{violet}("Unloading of mineral ions")` occurs at the `color{brown}("fine vein endings")` through `color{brown}("diffusion and active uptake")` by these cells.
● Mineral ions are frequently `color{brown}("remobilised,")` particularly from older, senescing parts.
● Older dying leaves export much of their `color{violet}("mineral")` content to `color{violet}("younger leaves.")`
● Similarly, before leaf fall in `color{brown}("decidous plants,")` minerals are removed to other parts.
● Elements most readily mobilised are `color{brown}("phosphorus, sulphur, nitrogen")` and `color{brown}("potassium.")`
● Some elements that are `color{violet}("structural components")` like `color{brown}("calcium")` are not remobilised.
● An analysis of the `color{violet}("xylem exudates")` shows that though some of the `color{violet}("nitrogen travels as inorganic ions,")` much of it is carried in the `color{brown}("organic form")` as amino acids and related compounds.
● Similarly, small amounts of `P` and `S` are carried as `color{brown}("organic compounds. ")`
● In addition, small amount of exchange of materials does take place between `color{brown}("xylem and phloem.")`
● Hence, it is not that we can clearly make a `color{brown}("distinction")` and say categorically that `color{violet}("xylem transports")` only `color{violet}("inorganic nutrients")` while phloem transports only `color{violet}("organic materials,")` as was traditionally believed.
● After the `color{violet}("ions")` have reached xylem through `color{brown}("active or passive uptake,")` or a combination of the two, their further transport up the stem to all parts of the plant is through the `color{brown}("transpiration stream.")`
● The `color{brown}("chief sinks")` for the mineral elements are the growing regions of the `color{violet}("plant")`, such as the apical and lateral meristems, young leaves, developing flowers, fruits and seeds, and the `color{violet}("storage organs.")`
● `color{violet}("Unloading of mineral ions")` occurs at the `color{brown}("fine vein endings")` through `color{brown}("diffusion and active uptake")` by these cells.
● Mineral ions are frequently `color{brown}("remobilised,")` particularly from older, senescing parts.
● Older dying leaves export much of their `color{violet}("mineral")` content to `color{violet}("younger leaves.")`
● Similarly, before leaf fall in `color{brown}("decidous plants,")` minerals are removed to other parts.
● Elements most readily mobilised are `color{brown}("phosphorus, sulphur, nitrogen")` and `color{brown}("potassium.")`
● Some elements that are `color{violet}("structural components")` like `color{brown}("calcium")` are not remobilised.
● An analysis of the `color{violet}("xylem exudates")` shows that though some of the `color{violet}("nitrogen travels as inorganic ions,")` much of it is carried in the `color{brown}("organic form")` as amino acids and related compounds.
● Similarly, small amounts of `P` and `S` are carried as `color{brown}("organic compounds. ")`
● In addition, small amount of exchange of materials does take place between `color{brown}("xylem and phloem.")`
● Hence, it is not that we can clearly make a `color{brown}("distinction")` and say categorically that `color{violet}("xylem transports")` only `color{violet}("inorganic nutrients")` while phloem transports only `color{violet}("organic materials,")` as was traditionally believed.