Essential Elements

There are 13 essential elements for plant growth:

6 are considered Major Elements:
7 are considered Micronutrients:
These elements are primarily taken up through the roots
Root uptake is determined by the plant’s need for specific nutrients
element uptake is substantial during rapid vegetative growth and development, but as the plant approaches maturity, uptake declines
an element must be in its ionic form in the soil solution to be absorbed by the plant roots
the soil solution is the moisture that is in the soil, which has dissolved ions in it, ready to be taken up by roots as they need it
the availability of the elements in the soil solution is dependent on several factors:
- moisture level of the soil
- pH of the soil solution
  - low pH (acidic) increases Mn, Fe, and Al uptake, but decreases Mg and P uptake
  - high pH (basic) increases Mo, but decreases Fe, Al, Mn, Zn, and B uptake
- temperature (N, P, K, S, Mg, B, Zn)
- interactions between some elements:
  - Phosphorous & Zinc
  - Phosphorous & Manganese
  - Potassium vs. Calcium vs. Magnesium

Xylem & Phloem

Upward movement of water and ions is handled by the xylem
- transpiration of water by the plant draws more water up, like sucking on a straw
- the rate of transpiration is mostly what determines the rate of the upward movement
- the rate of flow in the xylem ranges from 10 to 100 cm/hr
- there’s also pressure from the roots, pushing water & ions up the straw
downward movement of sugars and other metabolic products are channeled by the phloem
- but the movement can go both up & down, depending on the plant’s need to shuttle elements around based on need
- the rate of flow in the phloem is way slower than in the xylem
- the phloem is made up of living cells
there is some cross-transfer from the xylem into the phloem