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