POTASSIUM IN PLANT GROWTH AND YIELD dept of forestry mewar university

1. POTASSIUM INPOTASSIUM IN PLANTPLANT
GROWTH AND YIELDGROWTH AND YIELD
byby
Manzoor NabiManzoor Nabi
Mewar UniversityMewar University
RajasthanRajasthan

2. High K Low K
Low K High K
High K
Low K
Low K
High K

3. Control K Deficiency
Cakmak et al., 1994, J. Experimental Bot.

4. K
Water
Regime
Protein
Synthesis
Cell elongation Phloem Export
of Photosynthates
Photosynthesis
Enzyme
Activation
Alleviation of Effects
of Stress Factors
POTASSIUM IN CROP PRODUCTIONPOTASSIUM IN CROP PRODUCTION

5. K and Cell Elongation/ExtensionK and Cell Elongation/Extension
In most cases, cell extension is the
consequence of the accumulation of K in the
cells that is required for both stabilizing the
pH of the cytoplasm and increasing the
osmotic potential in vacuoles.
Cell elongation by GA isCell elongation by GA is
dependent on K supplydependent on K supply

6. Potassium is essentially needed for cell elongationPotassium is essentially needed for cell elongation
Potassium is essential for GA3
(gibberellin)-induced cell
elongation/extension, especially
under deep-seeding conditions
(seedling establishment!!!)
Potassium is needed for turgor
potential to avoid drought stress
in arid environment
Potassium and GA act
synergistically in elongating
cells
(Chen et al., 2001;
Plant Cell Environ. 24: 469-476)

7. Auxin-stimulated cell
elongation is also dependent
on presence of potassium.
There is a strong correlation
between expression of K-
channel proteins and cell
elongation following application
of auxin
Rogg et al., 2001, Plant Cell
Auxine
defective
line

8. TRH1 encoding a potassiumTRH1 encoding a potassium
transporter proteintransporter protein :: essential for root
tip growth. As cell elongation is driven by
turgor pressure, the operation of K
translocators is crucial for growth.
In the mutant lines without TRH1 protein
root hair formation was totally blocked..

9. Rigas et al., 2001, Plant Cell, 13: 139-151
Line with TRH1 Line without TRH1
Root Hair FormationRoot Hair Formation
With K proteinWith K protein Without K proteinWithout K protein

10. Wild
Type
trh1
Mutant
trh1trh1
+TRH1+TRH1
Scanning electron
micrographs
TRH mediating K transportTRH mediating K transport
essential for root hair formationessential for root hair formation
Rigas et al., 2001, Plant Cell, 13: 139-151

11. Potassium isPotassium is a criticala critical
mineral nutrientmineral nutrient in treein tree
growth and woodgrowth and wood
formation.formation.
In cambial region and xylem
differention zone a strong potassium
demand has been shown.
Langer et al., 2002; Plant Journal, 32: 997-1009
Differentiating xylem cells involved in wood
formation represent a strong sink for
potassium that provides the driving force for
cell expansion

12. Potassium concentration in xylem tissue,
cambium/xylem differention zone and phloem tissue
Langer et al., 2002; Plant Journal, 32: 997-1009
xylem
cambium/xylem
phloem
K nutritional status strongly affectsK nutritional status strongly affects
development of wood producing cellsdevelopment of wood producing cells

13. Xylem
expansion zone
CambiumCambium
Xylem
expansion zone
0.05 mM K0.05 mM K
10.010.0 mM KmM K
Langer et al., 2002; Plant Journal, 32: 997-1009
low Klow K adequate Kadequate K
Under K deficiency cambial and cell-Under K deficiency cambial and cell-
expansion zones lack 2-3 cell layers eachexpansion zones lack 2-3 cell layers each
Lack of cell divisions in the vessel development
region results in reduced wood production

14. The cambium cells divide andThe cambium cells divide and
make newmake new woodwood on the inside andon the inside and
newnew inner barkinner bark on the outside. Inon the outside. In
this way, a tree gets bigger aroundthis way, a tree gets bigger around
as it grows!as it grows!

15. Potassium is highly neededPotassium is highly needed for woodfor wood
production.production.
Potassium is driving force for expansionPotassium is driving force for expansion
of wood producing cellsof wood producing cells

16. Photosynthesis and PotassiumPhotosynthesis and Potassium
In K-deficient leaves photosynthesis is
impaired at different levels
stomatal CO2 flux into chloroplasts
conversion of light energy into chemical energy
rubisco activity/CO2 reduction
phloem export of photosynthates and,
detoxification of toxic O2 species

17. K K K
Photosynthesis and PotassiumPhotosynthesis and Potassium
During a mild K deficiency in cotton, increased stomatal resistance
is first to result in a decrease in net photosynthesis and, as the
deficiency becomes more acute, biochemical factors contribute.
Day 13 Day 26Day 19
Bednarz, et al. 1998, Environ. Exp. Bot. 39: 131-139
+K
-K
-K
+K
Severity of K deficiency

18. Effect of Varied K Supply on Photosynthesis in
CottonPhotosynthesisRate
(µmolm-2
s-1
)
K deficiency
Days
adequate K
Bednarz and Oosterhuis, 1999 ; J. Plant Nutr.

19. Decrease in photosynthesis with KDecrease in photosynthesis with K
deficiency becomes more distinct whendeficiency becomes more distinct when
plants are exposed to elevated COplants are exposed to elevated CO22
concentrationsconcentrations
Enhanced K requirement of plantsEnhanced K requirement of plants
when exposed towhen exposed to increasing COincreasing CO22 concentrationconcentration
in atmospherein atmosphere

20. 0.0
1.0
2.0
3.0
normal CO2
high CO2
AssimilationRate
[µmolCO2m-2
s-1
]
Effect of Elevated CO2
on Photosynthesis
at Varied K Supply
Adequate K
Low K
+K
-K
-K
+K
Barnes et al., 1995, Plant Cell Environ.

21. The transport of K+
across the plasma membrane and
tonoplast causes the turgor changes of guard cells. Stomata
open when guard cells accumulate potassium (red dots),
which lowers the cells’ water potential and causes them to
take up water by osmosis. The cells become turgid.
.K
Stomata regulating transpiration and COStomata regulating transpiration and CO22 uptakeuptake

22. Role potassiumRole potassium
in stomatalin stomatal
actionaction
When stomata opened,
the K content of guard
cells increased by
factor 2, indicating a
very rapid stomatal
opening by K uptake
openedopened
closedclosed
Langer et al., 2004; Plant Journal, 37: 828-838

23. PHLOEM TRANSPORTPHLOEM TRANSPORT
K plays a critical role in phloem transportK plays a critical role in phloem transport
SourceSource
SinkSink
KK

25. AKT2/3: a potassium
channel protein and
identified as photosynthate-
induced phloem K channel.
Flower induction and rosette
development of the
Arabidopsis with loss of
AKT2/3 function (akt2/3-1
mutant) is delayed
WT- AKT2/3 akt2/3-1 mutant
Potassium is essential for transport ofPotassium is essential for transport of
photosynthates into growing organsphotosynthates into growing organs
Deeken et al., 2002, Planta, 216: 334-344

26. Sucrose concentration
(mg Glucose equiv. g-1
DW)
Control
12 76
K Deficiency
Accumulation of Phosynthates in K-Deficient Source Leaves
Cakmak et al., 1994b, J. Experimental Bot.

27. Phloem Export of Sucrose
(mg Glucose equiv. g-1
DW 8 h-1
)
Control
3.4 1.6
K Deficiency
Decrease in Phloem Export of Sucrose by K-Deficiency
Cakmak et al., 1994b, J. Experimental Bot.

28. Relative distribution of total carbohydrates
between shoot and roots (%)
Control K Deficiency
16 3
9784
Cakmak et al., 1994a, J. Experimental Bot.

29. Plants suffering fromPlants suffering from
environmental stress factors suchenvironmental stress factors such
as drought, high light intensityas drought, high light intensity
and salinity have largeand salinity have largerr
requirement for potassiumrequirement for potassium

30. Photosynthesis
(µmolCO2m-2
s-1
)
Drought Stress
Low K
Adequate K
Potassium Improved Photosynthesis Under Drought
Stress
Sen Gupta et al., 1988, Plant Physiol.

31. Chlorophyll(gkg-1
FW)
MembraneDamage(%)
Control NaCl + K supplyNaCl
Alleviation of Salt Stress by K Supply
Kaya et al., 2001, J. Plant Nutr.

32. Increased salt sensitivity in the absence of KIncreased salt sensitivity in the absence of K
transporter protein.transporter protein.
AtHKT1 controls root/shoot Na+
distribution and counteracts
salt stress in leaves by reducing leaf Na+
accumulation.
Maser et al., 2002; FEBS Letters;531: 157-161

33. Growth of bean plants with low K
supply under low and high light
intensity
Low light High light

34. Plants grown under high light intensity requirePlants grown under high light intensity require
more Kmore K thanthan plants grown under low lightplants grown under low light
SHADEDSHADED
PARTPART

35. Partially shaded K-deficient bean leaves
Enhancement of leaf symptoms of
K-deficieny by high light
SHADED
NON-SHADED

36. REMEMBER:REMEMBER:

38.  Potassium deficiency makePotassium deficiency makess plants sensitive toplants sensitive to
environmental stress factors.environmental stress factors.
 Plants under environmental stress factors needPlants under environmental stress factors need
additional potassiumadditional potassium

39. S-H
S-H
MEMBRANE DNA PROTEIN
FREE RADICAL DAMAGE TO CRITICAL CELL CONSTITUENTS
O2
h.v. e-
LIPID
PEROXIDATION
PROTEIN
DAMAGE
MUTATION
CHLOROPHYLL
CHLOROSIS
S=S
1
O2 O2
._
H2O2 OH
.
S=S
CELL DEATH

40. ConclusionsConclusions
Potassium has several critical roles in plant
growth and yield formation including cell
elongation, maintenance of turgor pressure and
photosynthesis, stomatal closure, protein
synthesis and photoassimilate transport.
Potassium transporter proteins play critical role
in K uptake and translocation (contributing to cell
elongation) and tolerance to Na toxicity

41. Plants exposed to high light intensity or
grown under long-term sunlight conditions
like in southern countries in Northern
Hemisphere have much larger K
requirement
Improving K nutritional status of plants is
a major contributing factor to the protection
of plants from environmental stress factors
under marginal conditions

42. Remark:Remark: During the late growth stageDuring the late growth stage
(generative phase) plants can need(generative phase) plants can need
highhigherer amount of potassium becauseamount of potassium because
at this stageat this stage
 high amount of K is required for translocation ofhigh amount of K is required for translocation of
carbohydratescarbohydrates
 plants can be exposed to more light andplants can be exposed to more light and
 topsoil with high root density andtopsoil with high root density and highhigh KK
concentration can be dryconcentration can be dry (limited K uptake !)(limited K uptake !)
High need for late K application to foliar !!

43. Obrigado...Obrigado...