1. Plant Physiology
Mineral Nutrition

2. Mineral Nutrition in plants
Plants are:
Capable of making all necessary organic compounds from inorganic compounds and elements in the environment (autotrophic)
Supplied with all the carbon, hydrogen, and oxygen they could ever need (CO2, H2O)
Required to obtain all other elements from the soil so in a sense plants act as soil miners.

3. Mineral Nutrition in plants
The study of how plants obtain, distribute, metabolize, and utilize mineral nutrients.
“Mineral”: An inorganic element
Acquired mostly in the form of inorganic ions from the soil
“Nutrient”: A substance needed to survive or necessary for the synthesis of organic compounds

4. Classifying mineral nutrients
Amount required or present in plant tissue
Metabolic need for the mineral nutrient
Biochemical function(s) for the mineral nutrient
Mobility within the plant

5. Mineral macronutrients

6. Mineral micronutrients

7. Essentiality of mineral nutrients
Essential: Universal for all plants
– Absence prevents completion of life cycle
– Absence leads to deficiency
– Required for some aspect of mineral nutrition
• Beneficial: Often limited to a few species
– Stimulates growth and development
– May be required in some species
– Examples: Na, Si, Se

8. Essentiality of mineral nutrients
There are four basic groups:
Group one:
Forms the organic components of plants
Plants assimilate these nutrients via biochemical reactions involving oxidation and reduction
Group two:
Energy storage reactions or maintaining structural integrity
Present in plant tissue as phosphate, borate or silicate esters
The elemental is bound to OH group of an organic molecule

9. Biochemical functions of mineral nutrients

10. Essentiality of mineral nutrients
Group three:
Present in plant tissue as either free ions or ions bound to substrates such as the pectin component of the plant cell wall
Of particular importance are their roles as
Enzyme cofactors
In the regulation of osmotic potentials

11. Biochemical functions of mineral nutrients

12. Essentiality of mineral nutrients
Group four:
This last group has important roles in reactions involving electron transfer.
Some also involved in the formation/regulation of plant growth hormones – Zinc
The light reaction of photosynthesis - Copper

13. Biochemical functions of mineral nutrients

14. Techniques used to study plant nutrition

15. Nutrient deficiencies
Mineral nutrient deficiencies occur when the concentration of a nutrient decreases below this typical range
Deficiencies of specific nutrients lead to specific visual, often characteristic, symptoms reflective of the role of that nutrient in plant metabolism
Chlorosis
Necrosis

16. Nutrient deficiency v. sufficiency

17. Patterns of deficiency
The location where a deficiency reflects the mobility of a nutrient
Nutrients are redistributed in the phloem
Old leaves = mobile
Young = immobile

18. Patterns of deficiency
Older leaves on celery turning yellow while the growing points in the center remain green.

19. How are mineral nutrients acquired by plants?
Uptake through the leaves
Artificial: called foliar application. Used to apply iron, copper and manganese.
Associations with mycorrhizal fungi
Fungi help with root absorption
Uptake by the roots

20. The soil affects nutrient absorption
pH affects the growth of plant roots and soil microbes
Root growth favors a pH of 5.5 to 6.5
Acidic conditions weathers rock and releases potassium, magnesium, calcium, and manganese.
The decomposition of organic material lowers soil pH.
Rainfall leaches ions through soil to form alkaline conditions

21. The soil affects nutrient absorption
Negatively charged soil particles affect the absorption of mineral nutrients
Cation exchange occurs on the surface of the soil particle
Cations (+ve charged ions) bind to soil as it is –ve charded
If potassium binds to the soil it can displace calcium from the soil particle and make it available for uptake by the root

22. Plant roots – the primary route for mineral nutrient acquisition
Meristematic zone
Cells divide both in direction of root base to form cells that will become the functional root and in the direction of the root apex to form the root cap
Elongation zone
Cells elongate rapidly, undergo final round of divisions to form the endodermis. Some cells thicken to form casparian strip
Maturation zone
Fully formed root with xylem and phloem – root hairs first appear here

23. Root absorbs different mineral ions in different areas
Calcium
Apical region
Iron
Apical region (barley)
Or entire root (corn)
Potassium, nitrate, ammonium, and phosphate
All locations of root surface
In corn, elongation zone has max K accumulation and nitrate absorption
In corn and rice, root apex absorbs ammonium faster than the elongation zone does
In several species, root hairs are the most active phosphate absorbers

24. Why should root tips be the primary site of nutrient uptake?
Tissues with greatest need for nutrients
Cell elongation requires Potassium, nitrate, and chlorine to increase osmotic pressure within the wall
Ammonium is a good nitrogen source for cell division in meristem
Apex grows into fresh soil and finds fresh supplies of nutrients
Nutrients are carried via bulk flow with water, and water enters near tips
Maintain concentration gradients for mineral nutrient transport and uptake

25. Root uptake soon depletes nutrients near the roots
Formation of a nutrient depletion zone in the region of the soil near the plant root
Forms when rate of nutrient uptake exceeds rate of replacement in soil by diffusion in the water column
Root associations with Mycorrhizal fungi help the plant overcome this problem

26. Mycorrhizal associations
Not unusual
83% of dicots, 79% of monocots and all gymnosperms
Ectotrophic Mycorrhizal fungi
Form a thick sheath around root. Some mycelium penetrates the cortex cells of the root
Root cortex cells are not penetrated, surrounded by a zone of hyphae called Hartig net
The capacity of the root system to absorb nutrients improved by this association – the fungal hyphae are finer than root hairs and can reach beyond nutrient-depleted zones in the soil near the root

27. Mycorrhizal associations
Vesicular arbuscular mycorrhizal fungi
Hyphae grow in dense arrangement , both within the root itself and extending out from the root into the soil
After entering root, either by root hair or through epidermis hyphae move through regions between cells and penetrate individual cortex cells.
Within cells form oval structures – vesicles – and branched structures – arbuscules (site of nutrient transfer)
P, Cu, & Zn absorption improved by hyphae reaching beyond the nutrient-depleted zones in the soil near the root

28. Nutrients move from fungi to root cells
Ectotrophic Mycorrhizal
Occurs by simple diffusion from the hyphae in the hartig net to the root cells
Vesicular arbuscular mycorrhizal fungi
Occurs by simple diffusion from the arbuscules to the root cells
Also, as arbuscules are degenerating as new ones are forming, the nutrients may be released directly into the host cell

29. Manipulating mineral transport in plants
Increase plant growth and yield
Increase plant nutritional quality and density
Increase removal of soil contaminants (as in phytoremediation)

30. Periodic table of plant mineral nutrition

31. Vesicular-arbuscular mycorrhiza:Highly colonized root of maize dyed with trypan blue. Mycorrhizal formations are clearly visible: 1) vesicles; 2) arbuscules
Ectomycorrhiza: root tip of Pinus nigracolonised by ectomycorrhizal fungus