Chlorine, as compounded chloride, is necessary for
osmosis and
ionic balance; it also plays a role in
photosynthesis.
Sodium is involved in the regeneration of
phosphoenolpyruvate in
CAM and
C4 plants. It can also substitute for potassium in some circumstances.
Essentiality
- Essential for C4 plants rather C3
- Substitution of K by Na: Plants can be classified into four groups:
- Group Aa high proportion of K can be replaced by Na and stimulate the growth, which cannot be achieved by the application of K
- Group Bspecific growth responses to Na are observed but they are much less distinct
- Group COnly minor substitution is possible and Na has no effect
- Group DNo substitution is occurred
- Stimulate the growthincrease leaf area, stomata, improve the water balance
- Na functions in metabolism
- C4 metabolism
- Impair the conversion of pyruvate to phosphoenol-pyruva
- Reduce the photosystem II activity and ultrastructural changes in mesophyll chloroplast
- Internal osmoticum
- Stomatal function
- Photosynthesis
- Counteraction in long distance transport
- Enzyme activation
- Improves the crop quality e.g. improve the taste of carrots by increasing sucrose
In plants,
silicon strengthens
cell walls, improving plant strength, health, and productivity.[SUP]
[9][/SUP] Other benefits of silicon to plants include improved
drought and
frost resistance, decreased lodging potential and boosting the plant's natural pest and disease fighting systems.[SUP]
[10][/SUP] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant
biomass and
crop yields.[SUP]
[9][/SUP] Although not considered an essential element for plant growth and development (except for specific plant species -
sugarcane and members of the
horsetail family),[SUP]
[11][/SUP] silicon is considered a beneficial element in many countries throughout the world[SUP]
[12][/SUP] due to its many benefits to numerous plant species when under
abiotic or
biotic stresses.[SUP]
[13][/SUP] Silicon is currently under consideration by the Association of American Plant Food Control Officials (AAPFCO) for elevation to the status of a "plant beneficial substance".[SUP]
[14][/SUP][SUP]
[15][/SUP]
Silicon is the second most abundant element in earth's crust. Higher plants differ characteristically in their capacity to take up silicon. Depending on their SiO[SUB]2[/SUB] content they can be divided into three major groups:
- Wetland graminae-wetland rice, horsetail (1015%)
- Dryland graminae-sugar cane, most of the cereal species and few dicotyledons species (13%)
- Most of dicotyledons especially legumes (<0.5%)
- The long distance transport of Si in plants is confined to the xylem. Its distribution within the shoot organ is therefore determined by transpiration rate in the organs
- The epidermal cell walls are impregnated with a film layer of silicon and effective barrier against water loss, cuticular transpiration rate in the organs.
Si can stimulate growth and yield by several indirect actions. These include decreasing mutual shading by improving leaf erectness, decreasing susceptibility to lodging, preventing Mn and Fe toxicity.
