This document discusses crop physiology and stress tolerance research conducted by Dr. Md. Tariqul Islam. It summarizes key plant processes like photosynthesis, transpiration, mineral absorption, and growth. It also describes different types of photosynthesis (C3, C4, CAM) and factors influencing photosynthesis like photorespiration. The document outlines common plant stresses and techniques used to measure growth parameters and analyze crop physiology experiments.

1. Crop Physiological Research in Stress Tolerance
Dr. Md. Tariqul Islam
PSO & Head
Crop Physiology Division
Bangladesh Institute of Nuclear Agriculture
Mymensingh

2. Crop Physiology
Study of vital activities of crop plants
Photosynthesis Translocation
Respiration Osmosis
Transpiration Diffusion
Water absorption Ascent of sap
Mineral absorption Protein and fat metabolism
Growth Development
Gaseous exchange

3. Stress imposition and measures
• Water stress
• Salinity
• Temperature
• Waterlogging

4. Photosynthates: Food products (sugar and starches)
created through photosynthesis.
6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O
Photosynthesis > Sugar

5. Cross section of a leaf, showing the anatomical
features important to the study of photosynthesis:
stoma, guard cell, mesophyll cells, and vein

6. Stroma - fluid that fills inside of chloroplast
Thylakoids - disk shaped interconnected sacs
Grana - piled stacks of thylakoids

7. Translocation: Translocation is the movement
of sucrose and other organic materials from
one place to another within the plant body,
primarily through the phloem. 14C is used in
translocation.
Transport of organic substances in phloem
Sugars, amino acids, organic acids, protein,
potassium, chloride, phosphate, magnesium
etc. are transported in phloem.

10. C3 photosynthesis: C3 plants
Called C3 because the CO2 is first incorporated into a 3-carbon
compound.
Stomata are open during the day.
RUBISCO, the enzyme involved in photosynthesis, is also the
enzyme involved in the uptake of CO2.
Photosynthesis takes place throughout the leaf.
Adaptive value
more efficient than C4 and CAM plants under cool and moist
conditions and under normal light because requires less
machinery (fewer enzymes and no specialized anatomy).
Most plants are C3.

12. In C3 plants the photosynthesis, carbon
fixation and Calvin cycle all occur in a
single chloroplast.

13. C4 photosynthesis: C4 plants
Called C4 because the CO2 is first incorporated into a 4-carbon
compound.
Stomata are open during the day.
PEP Carboxylase uptakes CO2.very quickly,
Photosynthesis takes place in inner cells (requires special anatomy
called Kranz Anatomy)
Adaptive value
Photosynthesizes faster than C3 plants under high light intensity
and high temperatures because the CO2 is delivered directly to
RUBISCO, not allowing it to grab oxygen and undergo
photorespiration.
Has better Water Use Efficiency because PEP Carboxylase brings in
CO2 faster and so does not need to keep stomata open as much
(less water lost by transpiration) for the same amount of CO2 gain
for photosynthesis.
C4 plants include several thousand species in at least 19 plant
families. Example: corn, sugarcane

15. In C4 plants the photosynthesis takes
place in a chloroplast of a thin-walled
mesophyll cell and a 4-carbon acid is
handed off to a thick-walled bundle sheath
cell where the Calvin cycle occurs in a
chloroplast of that second cell. This
protects the Calvin cycle from the effects of
photorespiration.

19. CAM photosynthesis: CAM plants
Called CAM after the plant family in which it was first
found (Crassulaceae) and because the CO2 is stored in
the form of an acid before use in photosynthesis.
Stomata open at night (when evaporation rates are
usually lower) and are usually closed during the day. The
CO2 is converted to an acid and stored during the night.
During the day, the acid is broken down and the CO2 is
released to RUBISCO for photosynthesis.
Adaptive value
Better Water Use Efficiency than C3 plants under arid
conditions due to opening stomata at night when
transpiration rates are lower (no sunlight, lower
temperatures, lower wind speeds, etc.).
CAM plants include many succulents such as cactuses

20. In CAM plants the photosynthesis and
initial carbon fixation occur at night and a
4-carbon acid is stored in the cell's
vacuole. During the day, the Calvin cycle
operates in the same chloroplasts.

21. Photorespiration
The reaction of RUBISCO with oxygen and
metabolic processing of the resulting 2-PG is
called "photorespiration". It is called this
because it only occurs in the light
(mitochondrial respiration continues in
darkness) and because it consumes oxygen
and produces carbon dioxide, just like
mitochondrial respiration.

23. Causes of photorespiration
RUBISCO becomes less specific for CO2 as the
temperature rises.
CO2 dissolves in leaf cells less than O2. Higher ratio of
O2 favors oxygenation. Increasing CO2 concentration
also decreases oxygenation.
In normal air at 25°C, a well watered plant fixes oxygen
once for every 3 carbon dioxide fixations. If the
temperature increases or the plant is short of water,
however, the occurrence of oxygenation increases.

24. Is photorespiration beneficial to plant?
Photorespiration may protect the photosynthetic machinery
from excess ATP and reducing power from the light
reactions. This would occur under conditions of high light
and water stress, in which the stomates are closed and
there is low carbon dioxide in the leaf, which prevents the
carbon dioxide fixation reactions from using the ATP and
reducing power.
Under high light, CO2 levels around a plant may drop due to
rapid photosynthesis. This could allow reactive oxygen
species, such as superoxide, to be produced, and injure the
plant. Photorespiration may protect against reactive oxygen
species under these conditions by consuming oxygen and
releasing CO2
Photorespiration can supply amino acids for biosynthesis.

25. Transpiration
Loss of water from the surface of leaves and stems in the form of
water vapors
Cuticular transpiration: Water lost through the cuts and breaks in
the cuticular layers
Bark or lenticular transpiration: water lost from the bark and
lenticular in the stem
Stomatal transpiration: water is lost through stomata
Guttation
The loss of liquid water through special structures called Hydathods
or water stomata is called Guttation.
Contents of guttated water: The guttated water is not pure but
contains organic acids including amino acids, proteins, mineral salts
and even some enzymes.
Hydathodes: Hydathodes are simple openings found in the
epidermal layers. Just behind the pore an air cavity is present, which
is surrounded by parenchymatous tissues called Epithem.

27. Properties of water
both positive and negative charges
high specific heat, high freezing point
and rapid ionization
Water is a universal solvent

28. Water potential (Ψ) is a measure of the free energy of water
Osmosis is a kind of diffusion of solvent water molecules
across the cellular membrane

30. Imbibition: Hydrophillic substances like polysaccharides,
proteins etc. of cell walls and storage tissues attract
dipolar water to them. Water molecules in turn bind to the
charged surfaces. As a consequences the imbibent swells
in volume; such a phenomenon is called imbibition and
the pressure generated due to imbibition i.e., in the form of
swelling force is called Imbibition pressure.
Absorption of water: Capillary water

32. Growth phase
1. Vegetative (Germination to PI) phase
(Stages: Germination to emergence, seedling, tillering,
stem elongation)
2. Reproductive (PI to flowering) phase
(PI to booting, Heading or panicle exertion, flowering)
3. Ripening (Flowering to grain maturity)
(Stages: Milk grain, dough grain, mature grain)

33. Growth Analysis
CGR= W2-W1/P(T2-T1) gm-2d-1
RGR= LogeW2-LogeW1)/(T2-T1) gg-1d-1
NAR= W2-W1/(T2-T1) x LogeLA2-LogeLA1)/LA2-LA1) gcm-2d-1
LAR= A/W (Assimilatory material/Plant material)
LWR= LW/W (leaf weight/Plant material)
SLA= A/LW (leaf area/Plant material)