This document summarizes a study on the morphological plasticity of wheat roots under drought stress induced by polyethylene glycol (PEG) in hydroponic culture. The study investigated the effects of PEG at different wheat growth stages (seminal root formation, adventitious root formation, booting stage) on various root traits. PEG treatment decreased root hair length but increased root hair diameter during seminal root formation. During adventitious root formation and booting stage, PEG treatment increased several root traits like total root number and lateral root formation, but decreased traits like root and shoot dry weight. The results provide insights into wheat root responses to drought stress that could help breeders develop drought-tolerant wheat varieties.

1. MORPHOLOGICAL PLASTICITY IN WHEAT (Triticum
aestivum L.) ROOT DEVELOPMENT UNDER PEG-
TREATED HYDROPONIC CULTURE
Supervisor
Dr. Arif Hasan Khan Robin
Associate Professor
Co-supervisor
Dr. Md. Abdullah Al Bari
Associate Professor
Presented by
ID: 14AgGPB JJ02 M
Reg. No.: 36293
Department of Genetics and Plant Breeding
Bangladesh Agricultural University

2. Presentation Outline
• Introduction/background of the study
• Objectives of the study
• Materials and Methods
• Results
• Discussion
• Conclusions
• References
• Acknowledgements

3. Background
• Wheat is a vital crop and among cereals it stands next to rice
and maize.
• It grows in 0.43 million ha in rabi season and production is
around 1.3 M ton in our country
• In Bangladesh, wheat yield ranges from 4.5 to 5.5 t ha-1
• Potential yield is more than 9 t ha-1
Sources: FAOSTAT 2013; BBS, 2014; USDA, 2014; BARI, 2015

4. Background (Cont’d)
Sources:
FAOSTAT, 2013; USDA, 2014

5. Background (Cont’d)
• Wheat production is greatly affected by drought in the
country
• Grain yield of wheat reduced upto 50-66% during
reproductive stage, 18-53% at pre-anthesis and 13-38% at
post-anthesis.
• Efficient root system can exploit residual soil moisture to
avoid drought stress.
• Polyethylene glycol (PEG) can successfully create drought
condition at hydroponic culture
Sources: Michel and Kaufmann, 1973; Majid et al., 2007; Kiliç and Yağbasanlar, 2010

6. Background (Cont’d)
• So, three hydroponic lab experiments with PEG-8000
treatment was conducted in this research
Fig. 1 Root architecture in wheat
1. Primary root; 2. First order lateral
root; 3. Secondary order lateral root;
4. Branching interval; 5. Adventitious
root; θ1. Primary root branching
angle; θ2. First order lateral root
branching angle; θ3. Secondary
order lateral root branching angle.
1
2
3
4
5
θ1
θ3
θ2

7. Objectives
• To investigate the effect of 0.5% PEG-8000 mediated stress
on seminal wheat root development
• To explore the outcome of prolonged stress by PEG-8000 on
lateral roots and on root hairs of adventitious roots
• To perceive the responses of high resolute PEG-8000 on root
growth during booting stage of wheat.

8. Materials and Methods
 Experimental site and periods with spell
Growth chamber, Dept. of GPB, BAU. Duration April to
November
 A hydroponic experimentation
Three subsequent experimentation was conducted.
 Experimental Design
Completely randomized design(CRD).
 Plant materials and sources
Ten (10) elite wheat varieties. Collected from Wheat Research
Centre, Bangladesh Agricultural Research Institute (BARI)

9. Materials and Methods (Cont’d)
Variety Released year Yield (t ha1) Features
BARI Gom 21 (Shatabdi) 2000 3.6–5.0
Good level of tolerance to
terminal heat
BARI Gom 24 (Prodip) 2005 4.3–5.1
High yielding, but heat
sensitive
BARI Gom 23 (Bijoy) 2005 4.3–5.0 Moderately heat tolerant
BARI Gom 25 2010 3.6–5.0
Moderate level of tolerance to
heat stress
BARI Gom 26 2010 3.5–5.0
Tolerant to terminal heat
stress in late seeding
BARI Gom 28 2012 4.0–5.5
Tolerant to terminal heat
stress in late seeding
Kheri
Indigenous
cultivar
Sonalika 1973 1.7–2.1
Kanchan 1983 3.5 – 4.6 Leaf rust susceptible
Akbar 1983 3.5 – 4.5 Leaf rust tolerant
Table 1. Characteristics of the selected wheat varieties

10. Materials and Methods (Cont’d)
 Germination of seeds
• On polystyrene sheets inside the trays in the growth
chamber, temp 20±20 C and light 57±2 PPFD. After 2-3 days
germination occurred.
Fig. 2 Germination of seeds on polystyrene sheets.

11. Materials and Methods (Cont’d)
 Seedling raising and transferring into hardwood sheet
• After one week seed were grown in seedling. Timely nutrient
supply and thinning was done. Then transferred into
hardwood sheet.
A B
Fig. 3 A) Seedling raising; B) Transferred seedlings into hardwood sheet

12. Materials and Methods (Cont’d)
Nutrient solution
• Modified Hoagland solution. Electrical Conductivity (EC) is
maintained to 0.6-1.0
Table 2. Composition and concentration of the minerals used in the solution
Components Concentration
NH4NO3 62.46 mM
NaH2PO4.H2O 43.48 mM
MgSO4 39.46 mM
KNO3 59.35 mM
CaCl2.H2O 16.12 mM
H3BO3 3.43 mM
MnSO4.4H2O 0.76 mM
ZnSO4.7H2O 0.059 mM or 59.12 μM
CuSO4.5H2O 0.039 mM or 39.47 μM
NaMoO4.2H2O 0.009 mM or 9.13 μM
FeSO4 16.46 mM
EDTA 10.27 mM

13. Materials and Methods (Cont’d)
PEG treatment
Fig. 4 Controlled condition (0.0% PEG) Fig. 5 Treated with 0.5% PEG
Table 3. PEG application time and duration in the experimentations
Experiment Concentration Treatment given DAT Duration of treatment
Seminal
0.5%
20 10
Adventitious 54 20
Booting stage 75 20

14. Materials and Methods (Cont’d)
 Data recording
• Harvest 1: At 30 DAT during seminal root formation
• Harvest 2: At the 67 DAT during adventitious root formation
• Harvest 3: At 97 DAT during reproductive stage or booting
stage
 Preparation of Safranin Stain Solution
• Safranin solution of 0.5% was used for staining root hairs
 Measured variables
Live leaves Number of primary axis root Main axis root hair number Secondary axis root hair number
Growth status Primary root axis length Main axis root hair length Secondary axis root hair length
Total root number Primary root axis diameter Main axis root hair diameter Secondary axis root hair diameter
Number of phytomer Number of secondary root axis Primary axis root hair number Root dry weight
Main root axis length Secondary root axis length Primary axis root hair length Shoot dry weight
Main root axis diameter Secondary root axis diameter Primary axis root hair diameter Chlorophyll content

15. Materials and Methods (Cont’d)
 Measurement of traits under microscope
The measurements were done at 40x and 100x magnifications
under microscope.
Fig. 6 Measurements of root traits
under microscope.
a) diameter of main axis root
under control condition;
b) diameter of PEG-treated main
axis root;
c) number of lateral roots under
controlled condition;
d) lateral root numbers under
PEG-treated condition;
e) number of root hairs under
controlled condition;
f) number of root hairs under
PEG treatment.

16. Materials and Methods (Cont’d)
 Root dry weight and shoot dry
weight
Roots and shoots were put in the
oven with envelop and kept at 600 C
for 7 days
 Chlorophyll content measurement
With Chlorophyll meter (SPAD–502
Plus, 3V; 200mW), chlorophyll
content of live leaves were measured.
 Statistical analysis
Data were analyzed using MINITAB®
17 statistical software packages.
Fig. 7 Chlorophyll content
measurement

17. Results
 Length of root hair at seminal root formation
Fig. 8 Length of root hairs originated at the main root axis of wheat varieties for
two PEG treatments on 10 days after two (0.0% and 0.5%) PEG treatment (P<0.01
for treatment) Vertical bars indicate standard error of mean against each variable.

18. Results (Cont’d)
 Number of root hairs at adventitious root
Fig. 9 Number of root hairs originated from first order laterals (PA) of wheat
varieties on 20 days after two PEG treatment (P<0.001 for treatment, variety and
interaction of both traits). Vertical bars indicate standard error mean.

19. Results (Cont’d)
 Number of total roots per tiller
Fig. 10 Total number of roots per plant in wheat varieties on 20 days after two
PEG treatment (P<0.001 for treatment, variety and interaction of both traits).
Vertical bars indicate standard error mean

20. Results (Cont’d)
 Principle component analysis (PCA)
Table 4. Principal components and their coefficients from principal component analysis on
effect of low concentrated PEG-8000 mediated stress for seminal root development.
Variables PC1 PC2 PC3
TRt (no) -0.398 -0.278 -0.545
MAL (cm) -0.212 0.726 0.166
PAD (mm) 0.464 0.066 -0.488
MARHL (μ) 0.529 -0.264 -0.096
MARHD (μ) 0.504 0.057 0.410
nPARH (no) 0.219 0.565 -0.510
Eigenvalue 1.6575 1.2544 1.1255
% Variations explained 27.6 20.9 18.8
P value 0.001 0.75 0.948
SEM 0.17 0.145 0.173
PC-principal component; p-statistical significance, SEM-Standard error mean
Legends
TRt-Total root,
MAL-Main axis length,
PAD-Primary axis diameter,
MARHL-Main axis root hair length,
MARHD- Main axis root hair
diameter,
nPARH-Number of primary axis
root hair,

21. Results (Cont’d)
Legends
PC-principal component,
P-statistical significance
SEM-Standard error mean
LL-Live leaves,
GS-Growth status,
MAL-Main axis length,
MAD-Main axis diameter,
NPA-Number of first order laterals
nMARH-Number of main axis root hair,
MARHL-Main axis root hair length,
PARHL-Primary axis root hair length,
PARHD-Primary axis root hair diameter,
nSARH-Number of secondary axis root hair,
SARHD-secondary axis root hair diameter,
RDW-Root dry weight,
ChlC-Chlorophyll concent
Variables PC1 PC2 PC3
LL (no) -0.359 -0.126 0.052
GS (no) 0.340 0.097 -0.031
MAL (cm) -0.322 -0.075 0.090
MAD (mm) 0.166 -0.380 -0.120
NPA/2.5 mm (no) -0.160 -0.136 -0.449
DSA (mm) -0.244 -0.343 -0.132
nMARH (no) -0.133 -0.195 0.380
MARHL (μ) 0.086 -0.132 0.360
PARHD (μ) 0.204 -0.370 0.040
nSARH (no) 0.248 -0.295 -0.171
SARHD (μ) 0.117 -0.174 -0.279
RDW (mg) 0.048 -0.337 0.397
ChlC (SPAD unit) -0.319 0.111 -0.086
Eigenvalue 5.5673 2.9257 2.5019
% Variations explained 26.5 13.9 11.9
P value 0.001 0.001 0.522
SEM 0.071 0.066 0.060
Table 5. Principal components and their coefficients from principal component analysis
of prolonged PEG-8000 stressed adventitious root development.

22. Results (Cont’d)
Variables PC1 PC2 PC3
LL (no) -0.233 -0.318 -0.081
TRt (no) 0.135 -0.313 0.261
PAL (cm) 0.292 0.057 -0.333
nMARH (no) 0.291 -0.206 -0.153
MARHL (μ) 0.292 -0.078 -0.213
MARHD (μ) 0.173 -0.181 0.352
nPARH (no) 0.318 0.098 0.190
PARHL (μ) 0.250 0.055 -0.031
SARHL (μ) 0.007 0.153 -0.385
RDW (mg) 0.150 -0.374 -0.179
SDW (mg) 0.173 -0.395 -0.157
ChlC (SPAD unit) -0.119 -0.237 -0.451
Eigenvalue 7.1362 4.1364 2.6791
% Variations explained 35.7 20.7 13.4
P value 0.001 0.05 0.001
SEM 0.058 0.08 0.06
Legends
PC-principal component,
P-statistical significance
SEM-Standard error mean
LL-Live leaves,
TRt-Total root,
PAL-Primary axis length,
nMARH-Number of main axis root hair,
MARHL-Main axis root hair length,
MARHD- Main axis root hair diameter,
nPARH-Number of primary axis root hair,
PARHL-Primary axis root hair length,
PARHD-Primary axis root hair diameter,
SARHD-secondary axis root hair diameter,
RDW-Root dry weight,
SDW-Shoot dry weight,
ChlC-Chlorophyll concent
Table 6. Principal components and their coefficients from principal component analysis of
low span high resolute PEG-8000 on roots during booting stage experimentation.

23. Discussion
Methodology related issues
• Fresh water was used to avoid accumulation of toxic nutrient
residue
• The pH was always maintained to 5.5–6.5 to ensure maximum
availability of nutrients
 PEG-treatment difference
• Root production along with root hairs had increased under stress
to cope with the environmental changes
 Varietal difference
• Significant variation among the 10 wheat genotypes were found
due to their intra and inter species inherited genetic potentials
 Interaction difference of PEG and variety
• The significant interaction implies that the genotypes responded
differently to stress condition.
Source: Bugbee, 2003; George et al., 2013; Narayanan et al., 2014; Tamiru and Ashagre, 2015

24. Conclusion
 PEG-treatment decrease root hairs length on main root axis
by 24% and increment of their diameter by 5% at seminal
root development
 During adventitious root development PEG-treatment –
Increases Decreases
Number of root per tiller (33%) Number of live leaves per plant (29%)
Diameter of main root axis (8%) Length of main root axis (29%)
first order laterals (34%) Length of first order laterals (21%)
Diameter of root hairs at main root axis (6%) Length of second order laterals (23%)
Number of root hairs at first order laterals (28%) Number of root hairs at main root axis (35%)
Diameter of root hairs at first order laterals (14%) Length of root hair at main root axis (33%)
Number of root hairs at second order laterals (69%) Length of root hair at first order laterals (14%)
Diameter of root hairs at second order laterals (12%) Shoot dry weight (22%)
Root dry weight (17%) Chlorophyll content (20%)

25.  Root traits like total root per tiller, number of lateral root
formation and number of root hair development are crucial
 Cumulative trait association would be the key to avoid
drought condition
 Our results will add up the knowledge database and provide
a stimulus for wheat breeders for crop improvement
 Root responses influence plant performance that’s why it has
merits for full investigation
Conclusion (Cont’d)

26. References
o BBS 2014: Bangladesh Bureau of Statistics, Estimates of wheat 2013-14, Planning division, Ministry
of Planning, Agargaon, Dhaka, Government of the People's Republic of Bangladesh.
o BARI 2015: Data, 2015 — Agriculture Technology. Retrieved on 24 March, 2015, from
http://baritechnology.org /en/home/tech_commodity#result
o Bugbee B. 2003: Nutrient management in recirculating hydroponic culture. Paper presented at the
South Pacific Soilless Culture Conference-SPSCC 648.
o FAOSTAT 2013: Food and agricultural commodities production. Rome, Italy: FAO 2013.
o Kiliç H, Yağbasanlar T 2010: The effect of drought stress on grain yield, yield components and some
quality traits of durum wheat (Triticum turgidum ssp. durum) cultivars. Notulae Botanicae Horti
Agrobotanici Cluj-Napoca 38 164-170.
o Majid SA, Asghar R, Murtaza G 2007: Yield stability analysis conferring adaptation of wheat to pre-
and post-anthesis drought conditions. Pakistan Journal of Botany 39 1623-1637.
o Michel BE, Kaufmann MR 1973: The osmotic potential of polyethylene glycol 6000. Plant Physiology
51 914-916.
o Narayanan S, Mohan A, Gill KS, Prasad PV 2014: Variability of root traits in spring wheat germplasm.
PloS one 9 e100317.
o Tamiru S, Ashagre H 2015: In vivo evaluation of wheat (Triticum aestivum L.) cultivars for moisture
stress. International Journal of Agricultural Research, Innovation and Technology 4 55-60.
o USDA 2014: United States Department of Agriculture, Agricultural Statistics Annual, National
Agricultural Statistics Service, US.

27. ACKNOWLEDGEMENTS
 Dr. Arif Hasan Khan Robin (Supervisor)
 Dr. Md. Abdullah Al Bari (Co-supervisor)
 All the teachers of the Department of Genetics and
Plant Breeding
 All Departmental staffs
 My Departmental friends