Mechanisms of secondary nutrient movement into and within the plant

1. Mechanisms and Techniques of secondary nutrient
movement into and within the plant
Hema Boopathi
1

2. INTRODUCTION
✔ 17 essential nutrients – complete life cycle
✔ Ca, Mg and S - relatively large amount next to N,P and K 🡪 2o
Nutrient
✔ Plant take nutrients in ionic form from soil by root
✔ Inorganic macronutrients are usually present at low Conc. -
soil 🡪 accumulated against concentration gradient.
✔ Plants therefore have to develop adaptive and flexible
strategies for the acquisition of nutrients.
✔ Further mechanisms are present for (re)distribution throughout
the plant.
2
( Marschner, 1995 )

3. 3
Essential Plant nutrients

4. • Ion - Definition
– Ion is an atom or molecule which has lost
– or gained one or more electrons, making it
– positively or negatively charged
• Anion: A negatively charged ion
• Cation: A positively charged ion
4

5. CONTENT
Mechanisms of Ion uptake
✔Active absorption
▪ Protein lecithin theory
▪ Cytochrome pump theory
✔Passive absorption
▪ Mass flow theory
▪Contact exchange theory
5
Movement in Soil
✔Mass flow
✔Diffusion
✔Root Interception

6. Mechanism of Nutrient movement in Soil
Nutrients are absorbed by roots as ions
from the soil water or solution
• Diffusion – Movement of ions from a zone of
high conc. to zone of low conc.
• Mass flow – Movement of ions in soil solution
as water moves
• Root interception – Root grows to the
nutrient
6
(Marschner, 1995)

7. 7
Nutrient Mobility and plant uptake

8. 8

9. 9
Mechanism of Ion Uptake

10. Passive Absorption
• Absorption of nutrients along the concentration
gradient
• Absorption of nutrient without expenditure of
metabolic energy
Mass flow theory:
Nutrients are absorbed by the root along with
mass flow of water under the influence of
transpiration
10

11. Ion Exchange Theory
11

12. 12

13. 13

14. 14
Active absorption

15. 15

16. 16

17. 17
The pathways of mineral transport in roots

18. 18

19. 19
Plant Cell

20. Calcium
• Form – absorbed 🡪 Ca2+
• Avg conc. in plant dry wt 🡪 0.2 – 1.0 %
Functions:
• Cell wall – middle lamella
• Cell division and enlargement, Lipid
metabolism
• Activator of enzymes – ATPase
• Secondary messenger –Stress
20
(Fontes et al., 2017)

21. 21
Barber (1966)
Amount of Nutrients Supplied by Mass Flow, Diffusion, and Root
Interception - Corn Roots in a Alfisol

22. 22
Amounts of 45Ca2+ ions (cpm x 105) in various parts of tomato plants grown in
small (190 ml) or large (20,000 ml) containers for 40 d
(Choi et al., 1997)

23. 23
Pathway of Calcium movement to xylem
( White, 2000)

24. 24
( White, 2000)
Translocation of calcium with the distance from root tip

25. Total Uptake and translocation of Calcium in rice
25 Kobayashi et al. (2013)

26. 26
(White and Broadley, 2003 )
The relationship between Calcium concentration in soil
solution ([Ca2+]ext) and shoot Calcium content

27. Distribution of Calcium, Magnesium and Sulphur in
mature cotton plants
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Plant Parts Ca Mg S
% of Total Uptake
Stems 19 17 14
Leaves 64 38 39
Burs 14 14 22
Seed 3 31 25
Mullins and Burmester (1995)

28. Calcium uptake and distribution
28
(Maathuis, 2009)

29. Calcium Transporters in Arabidopsis thaliana
29
Sanders et al. ( 2002)

30. Ion homeostasis mechanism – Calcium Signaling
( Bahmani et al., 2015 )30

31. 31
Ca in soil solution
Plant root epidermis
Mass flow
Root Xylem
Apoplastic way in apical root,
symplastic way in matured
root using Calcium channels
Leaf Xylem
All other parts
Transpiration Pull
Diffusion

32. Magnesium
• Form – absorbed 🡪 Mg2+
• Avg conc in plant dry wt 🡪 0.1 – 0.4 %
Functions:
• Chlorophyll – central head in chlorophyll structure
• Activator of enzymes – carboxylase and hexokinase
• Binding ribosome units during protein synthesis
• Important nutrient in plant growth and development
32
(Guo, 2017)

33. Magnesium in plant
• Total Mg concentration ranges from 15 – 25 mM (Mooraw
and Maguise, 2008).
• However, most Mg ions are bound or incorporated into
cellular components, which leaves free cytosolic Mg2+ in the
range of 0.4 to 0.5 mM.
• Typically 15– 20% of total leaf Mg is in chlorophyll (White &
Broadley, 2009), although this percentage can be higher or
lower depending on plant Mg status.
• Phloem loading of carbohydrates depends on adequate Mg
levels, as Mg deficient leaves accumulate starch and sugars
(Marschner, 1995).
33

34. 34
Barber (1995)

35. Contribution of root interception, mass flow and diffusion to
the Potassium and Magnesium demand of maize in soil
35
Barber (1995)

36. Contribution of mass flow to measured uptake of Potassium
and Magnesium to spring wheat and sugar beet
36
Strebel and Duynisveld (1989)

37. Magnesium Uptake and Distribution
37
(Maathuis, 2009)

38. Multi compartment transport box for Magnesium
tracer study
Kobayashi et al. (2013)
38

39. Total Uptake and Translocation of Magnesium in rice
39 Kobayashi et al. (2013)

40. Distribution pattern of Magnesium in plant parts of rice
40 Kobayashi et al. (2013)

41. 41
Mg in soil solution
Plant root epidermis
Mass flow
Root Xylem
Apoplastic way in apical root,
symplastic way in matured
root using MRT transporters
Leaf Xylem and Phloem
All other parts

42. Sulphur
• Form – absorbed 🡪 SO4
2-
• Avg conc in plant dry wt 🡪 0.1 – 4.0 %
Function:
✔Components of amino acids like cysteine, cystine
and methionine
✔ Protein and coenzyme
42

43. 43
(Havlin et al., 2005 )
Rates of Root interception, Mass Flow and Diffusion in Ion
Transport to Corn Roots

44. Autoradiography showing the accumulation of sulphate
as a result of mass – flow in corn
44
Dark areas represent the areas of
S35 accumulation.
Walker and Barber (1962)

45. Overview of plant Sulphur assimilation Pathway
45
Jez et al. (2016)

46. S assimilation with compartmentation
46
Kopriva et al. (2015)

47. S – Transporter in Oil seed
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48. Topology of SO4
2- Transporter
48
Smith et al. (2000)

49. 50
SO4
2- in soil solution
Plant root epidermis
Mass flow
Root Xylem
Apoplastic way in apical root,
symplastic way in matured root
using MRT transporters
Root Phloem
All other
parts
Reduction of sulphur to
S compounds and
aminoacids

50. Techniques of secondary nutrient movement
✔ Radiotracer methods
✔ Analyses of exudates from
transported systems using
aphid stylectomy.
✔ Microelectrode Technique.
✔ Patch-clamp technique.
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51. 52
Microelectrode Technique.
Patch-clamp technique.

52. 53

53. Process of nutrient uptake in soil – plant system
OVERALL PROCESS
54
Pitman (1972)

54. 55
Literature Collected
No. of Research article collected : 20
No. of Abstracts collected : 16
No. of Reviews collected : 10