Essential Nutrients for Plant Growth

1. Unit 1 Chapter 5 Mineral Nutrition

2. Essential nutrients Essential elements: an intrinsic component in the structure or metabolism of a plant, its absence causes severe abnormalities in plant growth, development, or reproduction. There are a total of 17 essential mineral elements: Macronutrients: N, P, K, Ca, Mg, Sulfur, Carbon, Hydrogen, Oxygen Micronutrient Cl, Fe, Boron, Mn, Zn, Cu, Ni, Mo

3. Figure 12.1 Solution culture (hydroponics) Aeration to keep plants from anoxia Solution must be replenished regularly or the growth of plants will be stopped. Container painted black or wrapped to keep out light so the growth of algae will be reduced.

4. Figure 5.2 Various types of solution culture systems Solution culture Hydroponics

5. Plant and Inorganic Nutrients • The acquisition of inorganic nutrients (minerals) is part of the plant nutrition. • Plant nutrition can be viewed as two parts: organic nutrition, which is mainly dealing with photosynthesis; and inorganic nutrition. • Organic nutrition (photosynthesis) and inorganic nutrition are highly interdependent.

6. Essential nutrient elements There are 17 essential elements in plants. Absence of any one of the element could prevent plants from completing its normal life cycle or some essential plant constituent or metabolite will not be manufactured. According to the relative concentrations found in tissue (or the relative concentrations required in nutrient solution), these 17 elements are classified as macronutrients and micronutrients (trace elements). Macronutrients are more than 10 mmole per kilogram of dry weight, micronutrient are less than 10 mmole per kilogram of dry weight.

7. Chapter Outline Mineral nutrition study methods Essential and benefical elements Macronutrients and micronutrients The metabolic roles of the 17 essential mineral elements The concept of critical and deficient concentration Deficiency symptoms Micronutrient toxicity

8. Because in solution culture the replenishment of nutrient solution is a disadvantage, other methods were developed. In these methods, plants were grown in nonnutritive medium (perlite or vermiculite) and fresh nutrient solution was applied from the top (slop culture) or slowly dripping from a reservoir (dripculture). perlite vermiculite

9. Figure 12.2 Nutrient film technique (subirrigation)

10. Table 12.4

11. Beneficial elements Sodium, Silicon, Cobalt, and Selenium are required for some plants. Because they are not required for all plants, they are called beneficial elements instead of essential elements.

12. Beneficial elements - Sodium Sodium is required for plants that have C4 photosynthetic pathway (ex. bladder salt bush). For these, when sodium is deficient, they will exhibit symptoms like - reduced growth - chlorosis (yellowing due to loss of chlorophyll) - necrosis (dead tissue) of the leaves

13. Beneficial elements – Silicon Silicon is particularly beneficial for grasses. It accumulates in the cell walls to prevent lodging(stems bent over by heavy winds or rain). It also has rolesin fending off fungal infections. Beneficial elements - Cobalt Cobalt is required for nitrogen fixing bacteria. So it was found to be a requirement for legumes. However, if fixed nitrogen is provided to legumes the need of cobalt cannot be demonstrated.

14. Beneficial elements - Selenium Selenium are probably not required for plants. Although selenium is toxic to most plants and animals, Astragalus spp. are known to accumulate selenium. Eating Astragalus spp. causes alkali poisoning or blind-staggers in grazing animals. They are called “loco weeds”.

15. Nutrient roles and deficiency symptoms It is difficult to categorize the nutrient element according to their functions because one nutrient element could have several different functions.

16. Figure 5.5 Influence of soil pH on the availability of nutrient elements in organic soils • Soil pH has a large influence on the availability of mineral nutrients to plants

17. The soil is a complex substrate – physically, chemically, and biologically. The size of soil particles and the cation exchange capacity of the soil determines the extent to which a soil provides a reservoir for water and nutrients • A soil with higher cation exchange capacity generally has a larger reserve of mineral nutrients

18. Because the ability of exchange cations of colloidal surfaces, the colloidal fraction of soil is the principal nutrient reservoir for the soil.

19. Protons (hydrogen ion) can replace most of the cations easily. Therefore, plant roots also secrete protons to make cations available for absorption. Acid rain will wash out the cations of soil solutions and colloidal surfaces by the same mechanism of cation exchange.

20. Ion uptake by roots • The most popular organ for study of ion uptake is excised roots. • So called “low-salt roots” are grown under conditions (see fig. 13.11 for the legend) that encourage depletion of nutrient elements.

21. Roots Plants develop extensive root systems to obtain nutrients Roots have a relatively simple structure Roots continually deplete the nutrients from the immediate soil around them, and roots grow continuously. Different areas of the root absorb different ions: in barley, Ca absorption is restricted to the apical region; K, nitrate, and ammonium can be absorbed at all locations of the root surface. In corn, elongation zone has the maximum rate of K and nitrate absorption.

22. Figure 5.7 Fibrous root systems of wheat (a monocot)

23. Figure 5.8 Taproot system of two adequately watered dicots

24. Root-microbe interactions Bacteria mucilages (mucigels) proteoid roots Mycorrhiza ectomycorrhizae endomycorrhizae VAM (vasicular-arbuscular mycorrhiza)

25. Figure 5.9 Diagrammatic longitudinal section of the apical region of the root

26. Ectomycorrhizae -this family of mycorrhizae is restricted to temperate trees and shrubs such as pines and beech. -they are short, highly branched, and ensheathed by a tightly interwoven mantle of fungal hyphae. -it also penetrates the intercellular of apoplastic spaces of the root cortex, forming a intercellular network

27. Because bacteria can enhance nutrient uptake of roots, the Golgi apparatus of root cells (root cap cells, young epidermis cells, and root hairs) secrete polysaccharide-based mucilages to attract bacteria. Mucilages Bacteria Colloidal soil particles

28. Endomycorrhizae -it is found in some species of virtually every angiosperm family and most gymnosperms. -it is developed extensively within cortical cells of the host roots. -VAM (vesicular-arbuscular mycorrhiza) is the most common type of endomycorrhiza. -VAM forms arbuscule with host cells without penetrating protoplasm of its host. Arbuscules increase contact surface area by two or three times.

29. Figure 13.15 Maize seedlings that is not colonized by myccorrhiza.

30. Figure 13.16 Nutrient depletion zone defines the limits of the soil from which the root is able to readily extract nutrient elements. Mycorrhiza can extend the nutrient depletion zone for a plant.

31. Figure 13.12 = Apparent free space (AFS) Cations in AFS is lost Ca2+ is being exchanged by Mg2+ Simple diffusion is occuring in AFS

32. Ions lost in the AFS is a two-step process • Because cell wall component (galacturonic acid residues of pectic acid), which is the main constituent of AFS, is negatively charged, cations will not be readily lost once they have been absorbed. However, it can be exchanged.

33. Apparent free space (AFS) is the cell wall and intercellular spaces of the epidermis and cortex of the roots (regions of the root that can be entered without crossing a membrane; apoplast space of the root epidermal and cortical cells). AFS occupied about 10%~25% of root volume. AFSincludes space accessible to free diffusion and ions restrained electrostatically due to charges that line the space.

34. Figure 5.11 Root epidermis (rhizodermis), cortical cells Endodermis + suberized Casparian band Vascular tissues: vessel elements, parenchyma cells Symplast Apoplast Ion Symplast Apoplast

35. Fig. 13.3 Facilitated diffusion

36. Facilitated diffusion The solutes are transported by transport proteins (channels and carriers). The direction of transport is still determined by the concentration gradient.

37. Active transport - leads to accumulation of solute - requires energy - unidirectional - pumps

38. Selectively uptake of ion

39. Although [K+] is higher inside than outside, due to the [cation] of the cell wall space is higher than cytosol, so K+ will still move into the cell until the membrane potentials on the both sides reaches equilibrium.

40. ATPase-proton pumps are the major factor in the membrane potential of most plant cells plasma membrane-type proton-pumping ATPase (P-type ATPase) tonoplast-type proton-pumping ATPase (V-type ATPase antiport symport Uncharged solute (ex. sugars)

41. The other function of Casparian band Because the ion concentration of stelar apoplast is much higher than in the surrounding coretx, the other function of Casparian band could be to prevent loss of ions from the stele by diffusion. Inhibitors of ion transport such as cycloheximide suggests that ion release into the vessels is a different kind of process than ion uptake by the roots.

42. The uptake of ions is not uniform along the length of the root. What takes up in the tip remains in the root.

43. At this range additional increments in nutrient content will have no beneficial effect on growth. Growth falls off sharply in this range The concentration of that nutrient, measured in the tissue, just below the level that gives maximum growth.

44. Some symptoms could tell us more about this particular nutrient Chlorosis (yellowing) deficiency of this nutrient element causes plant unable to synthesize chlorophyll Symptoms first appear at older tissue this nutrient element is probably mobile Symptoms first appear at younger tissue this nutrient element is probably immobile

45. Mineral deficiencies • If an essential element is mobile, deficiency symptoms tend to appear first in older leaves. • Deficiency of an immobile essential element becomes evident first in younger leaves.

46. Si, Ni, Mn ??

47. Nutrients N: component in amino acids, DNA Deficiency: chlorosis in old leaves. S: component in amino acids, vitamins. Deficiency: chlorosis in mature and young leaves. Veins and petioles show a very distinct reddish color.

48. Nitrogen (NO3-, NH4+) -N

49. Phosphorus deficiency symptoms intense green coloration of the leaves malformed leaves and necrotic spots (anthocyanin accumulation) rapid senescence and death of the older leaves shortened and slender stems reduced yield of fruits and seeds Excess abundant growth of the roots

50. Nutrition • Group 2: energy storage or structural integrity P: components in DNA, RNA, phospholipids, ATP, etc Deficiency: stunted growth, dark green coloration containing necrotic spots; slight purple coloration