The document discusses various mechanisms of nutrient and water uptake in plants. It describes nutrient absorption mechanisms including ion exchange, channels, carriers and active transport pumps. It also discusses the transport of absorbed nutrients within plant cells and tissues, focusing on passive transport mechanisms like channels and carriers, as well as active transport mechanisms like proton pumps and ABC transporters. Finally, it covers the long-distance transport of organic molecules like photosynthates from source to sink tissues, known as translocation, which primarily occurs via the phloem as per the Munch pressure flow hypothesis.

1. The branch of biology that deals with
the vital functions of the plant

2. Chapter hr
1. Introduction to crop physiology and its importance in agriculture. 2
2. Structure and physiology of cell and cell organelles; cell wall, cell membrane. 1
3. Water potential and its components. Diffusion and osmosis. 1
4. Mechanism of water absorption. Crop–water relations. 1
5. Transpiration, significance, transpiration in relation to crop productivity, anti-transpirants, water use efficiency. 1
6. Stomata, structure and function- mechanism of stomatal movements. 1
7. Water deficit stress– drought tolerance mechanisms. 1
8. Nutrient absorption mechanisms. Foliar nutrition and hydroponics. 1
9. Nutrio-physiology, definition. Classification of plant nutrients based on quantity, mobility and function. 1
10. Functions of plant nutrients. Deficiency and toxicity symptoms of plant nutrients. 2
11. Photosynthetic pigments. 1
12. Photosynthesis: Light reactions– Photosynthetic electron transport chain. 1
13. Photosynthesis: Light independent reactions– Calvin cycle. 1
14. C4 and CAM mechanisms. 1
15. Photorespiration-Significance. 1
16. Respiration and its significance. 1
17. Glycolysis; TCA cycle. 1
18. Mitochondrial ETC and Alternate respiration. 1

3. Chapter hr
19. Plant growth regulators: Biosynthesis and physiological role of auxin, gibberellins, cytokinin, ABA, ethylene 2
20. Novel PGRs and commercial applications in agriculture 1
21. Physiological aspects of growth and development- Rice, Coconut, Cassava, Black pepper, Banana 2
22. Physiology of flowering-Photoperiodism and vernalisation in relation to crop productivity, Photoreceptors 2
23. Growth analysis, measurement of growth, role of physiological growth parameters in crop productivity-
RGR, CGR, NAR, LAI, SLA, HI
1
24. Physiological disorders in crop plants 1
25. Recent developments in Plant Physiology 1

4. Fundamentals of Crop Physiology
Nutrient Absorption Mechanisms.
Foliar Nutrition and Hydroponics.
Krishna Kumar G
Ph.D., ICAR-IARI
Plant Physiology
Asst. Professor
KAU-CoA
Lecture 8

6. The Water and Nutrient Uptake

7. Uptake:
The entry of nutrients from soil solution to the plant roots is
called uptake.
Ion Exchange
Anion Exchange
Cation Exchange
Nutrient Uptake
Mechanism of Nutrient Uptake

8. Na+
Na+
Cl-
Cl-
Electrode:
Anode
(+ve)
Electrode:
Cathode
(-ve)
Ion:
Anion
-ve charged ion
Ion
Cation
+ve charged ion
+
̶
̶
̶
̶
̶
+
+
+
+
NO3
-, PO4
-
K+, Ca2+, Mg2+

9. Ion Exchange
Anion Exchange
The roots release OH- or CO3
- in exchange of NO3
-, PO4
-, etc.
Cation Exchange
The roots release H+ in exchange of K+, Mg2+, etc.
Mechanism of Nutrient Uptake

10. Transport
Molecular and ionic movement from one location to another
is known as transport.
Classification of Transport Mechanisms
Passive Active
Nutrient Transport Inside Plant Cells

11. Nutrient Transport Inside Plant Cells

12. Nutrient Transport Inside Plant Cells

13. Potassium Channel; Aquaporins
Passive Transport Mechanisms
Channels Carriers

14. • Channels are transmembrane proteins that function as
selective pores, through which molecules or ions can diffuse
across the membrane.
• Channel transport is limited mainly to ions or water.
• Gated: They open only under stimuli.
[A] Protein Channels

15. • Carrier proteins do not have pores that extend completely across
the membrane.
• Carriers hold the protein at a specific site.
• There will be conformational change in protein.
• The ion will be pushed across the membrane.
[B] Protein Carriers

16. Carrier Mediated Transport
• Symport
Secondary Active/Facilitated Diffusion
• Antiport
• Uniport

17. [C.a] Pumps
Active Transport Mechanisms

18. Proton Pumps
ATPase
ATP
synthase

19. [C.b] ABC Transporter

20. All Transport Mechanisms

22. Ionophore Mediated Membrane Transport
 An ionophore is a chemical species that reversibly binds and
transport ions across membrane.
 It is synthesised by a variety of microbes, fungi and plants.
 Ionophores are generally lipid-soluble entities that transport
ions across the cell membrane.
 They are of two types:
Channel ionophores and Carrier ionophores.

23. Ionophore Mediated Membrane Transport

24. Ionophore examples:
Protonophore ; Phytosiderophore
 Ionophores that transport hydrogen ions (H+, i.e. protons) across the
cell membrane are called protonophores.
 Iron ionophores and chelating agents are collectively called
siderophores.
 NB: Siderophores can also chelate Cu, Zn, Mn,…

25. Translocation
The transport of organic molecules from source to sink
is called translocation.
Organic molecules?
Source?
Sink?

26. Tissue for Translocation
Phloem is the living tissue in vascular plants that transports the
soluble organic compounds made during photosynthesis.
Medium to dissolve Solutes
Water
Soluble organic compounds
Photosynthates Eg:- Sucrose, trehalose, etc
Phloem

27. Water+Sugar
Water
1930: Ernst Munch – Pressure flow hypothesis/Munch hypothesis.
Tissue for Phloem Translocation

28. Water+Sugar
Water
1930: Ernst Munch – Pressure flow hypothesis/Munch hypothesis.
Phloem transport is driven by osmotically generated pressure gradient between supply
point (source) and storage end (sink). The organic solution flow as a mass through
sieve elements of phloem from source to sink.
There are 8 steps in Munch hypothesis
•Photosynthesis in leaf parenchyma (source tissue).
•Loading into companion cell.
•Plasmodesmatal transport from companion cell to sieve tube.
•The entry point cells of sieve tube have concentrated sugars.
•Dragging of water from xylem by osmosis to sieve tubes (due to high sugar
concentration).
•In sieve tubes- Movement of sucrose containing cell sap to ‘sucrose-less’ direction.
•Unloading of sucrose to the storage/sink tissues
(where it gets converted to starch <non-osmotic] ; eg:- Potato tuber).
•Transport of water back to xylem.

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