MINISTRY OF EDUCATION AND TRAINING
HA NOI NATIONAL UNIVERSITY OF EDUCATION TRAN THI THANH HUYEN

RESEARCH ON SOME PHYSIOLOGICAL AND BIOCHEMICAL
INDEXES RELATED TO DROUGHT TOLERANCE,
PRODUCTIVITY AND QUALITY OF SOME SESAME VARIETIES
(SESAMUM INDICUM L.) CULTIVATED IN HANOI

Major: Plant physiology
Code: 62. 42. 30. 05
Summary of doctoral thesis of biology



Reviewer 3: Prof. Dr. Le Tran Binh
Thesis defense will be at the Council for State Level Thesis Marking at Hanoi National
University of Education
At (time) on … (date)…… 2011
The thesis can be found at:
- National Library of Viet Nam
- Library, Hanoi National University of Education

Publications related to the thesis

1. Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Lan Phuong,

5. Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Thanh Thuy,
Nguyen Thi Minh Nguyet (2010), “Study in genetic diversity of sesame
(Sesamum indicum L.) using RAPD”, Journal of Biotechnology, Volume
8, No 4, pp. 1847-1853. 6. Tran Thi Thanh Huyen, Nguyen Nhu Khanh (2011), “Study on
indicators of water exchange that related to drought resistance of 20
sesame varieties”, Journal of Science, VietNam National University, HaNoi


1

INTRODUCTION
1. Background
During the living process, plants are always influenced by external factors such
as drought, cold weather, heat, salinity, flooding, insects, etc. Among these factors,
high temperature, cold weather, wind and drought are considered the main causes to
the dehydration in plants. A long drought can affect relevant metabolistic reactions,
different stages of plant growth and development leading to low productivity and
quality of agricultural products and possible dead plants. Drought is a complicated
phenomenon and is widely regarded as the most important factor to optimise plant
production.
Sesame (Sesamum indicum L.) is among terrestrial plants with a wide range of
adaptation and traditionally cultivated in different types of soil. Sesame is known as
“the queen of oil producing plants” with high nutritional values. In sesame seeds, the
high lipid content of 45 – 54%, especially with presence of unsaturated fatty acids
(oleic, linoleic, linolenic), essential amino acids, antioxidant compounds (sesamin,
sesamol, sesamolin and vitamin E), has increased values of sesame seeds. Many
studies in the world have been carried out to evaluate these characteristics of sesame.

- To identify genetic relationships between sesame varieties of good and poor
drought tolerance among the 20 pre-screened sesame varieties.
- To assess yield and seed quality of some drought tolerant sesame varieties
selected during experiments of the study conducted in Hanoi.
3. Scientific and practical significance of the study
Scientific significance
- Data collected in the study will be scientific evidence on physiological and
biochemical reactions related to drought tolerant ability of sesame varieties under the
study.
- Study results identified the genetic relationship between sesame varieties of
high and poor drought tolerance among 20 sesame varieties under the study.
- The results of sesame seed analysis will have additional contributions of
scientific evidence, which is significantly important to nutritional values and uses of
sesame seeds.
Practical significance
- Differences between physiological and biochemical criteria of high and poor
drought tolerant varieties can be used for selection and generation of high drought
tolerant varieties with high yield and good quality so as to reduce input materials and
labour in selecting drought tolerant varieties.
- Study results on sesame seeds are also a criterion of reference for selections
of sesame varieties with both drought tolerance and good seed quality to be used in
industries of sesame exploitation and processing as well as in medicine and
pharmacy.
4. New contributions of the thesis
- Identified physiological and biochemical differences between high and poor
drought tolerant varieties. On that basis, classified sesame into different groups of
sesame with drought tolerance at different levels. Proposed V5 and V14 varieties
which are highly drought-tolerant but can give stable production and good seed quality.
- Combined the assessment of drought tolerance with the analysis of
genotypes with RAPD techniques and showed different sesame varieties with

2.2.3. Identification of genetic diversity by RAPD (Random Amplified
Polymorphic DNA): DNA isolation was based on Doyle method; RAPD-PCR was
carried out using the method of William et al with 26 random primers
CHAPTER III. RESULTS AND DISCUSSIONS
3.1. Assess dehydration resistance of 20 sesame varieties in researched area
3.1.1. Impacts of drought on physiological criteria
3.1.1.1. Rapid assessment of drought tolerance
We rapidly assessed drought tolerance of 20 sesame genotype during seedling
period in laboratory including: rate of un-withered plant, rate of recovered plant and
drought tolerance indexes. V14 and V5 had the highest drought tolerance indexes,
which reached 22085 and 21541, respectively. Two varieties had the lowest drought
tolerance indexes were V4, V8, which reached 13675 and 12646 (the higher the
drought tolerance index is, the higher the drought tolerance capacity is)
Based on drought tolerance indexes in the table 3.1, initially we divided 20
varieties into three groups: the good drought tolerance group has two varieties: V14
and V15; low drought tolerance group has two varieties: V4 and V8; other 16 varieties
have medium drought tolerance indexes including: V18, V17, V13, V16, V12, V19, V11,
V6, V15, V2, V1, V9, V10, V3, V7, V20 varieties. 4

Table 3.1. Drought tolerance indexes of 20 sesame varieties
One day after
drought
treatment
Three days

V10 100.00 100.00 90.34 73.55 60.45 54.62 16838 15
V11 97.34 100.00 94.12 74.14 62.50 59.13 17410 9
V12 95.17 100.00 93.24 80.12 69.53 60.43 18114 7
V13 100.00 100.00 90.16 82.14 76.11 61.14 18809 5
V14 100.00 100.00 96.67 99.12 84.61 72.42 22085 1
V15 96.87 100.00 88.78 79.56 66.67 53.77 17201 11
V16 100.00 100.00 87.99 87.56 64.67 62.75 18402 6
V17 100.00 100.00 91.26 84.34 76.44 61.56 19108 4
V18 99.12 100.00 92.13 83.15 78.22 64.15 19340 3
V19 100.00 100.00 89.45 77.84 76.24 49.67 17578 8
V20 94.37 100.00 72.42 63.69 64.75 43.66 14012 18
(% UWP: rate of un-withered plant; % RP: rate of recovered plant)
3.1.1.2. Soil’s wilting coefficient
We identified soil’s wilting coefficient in order to determine water absorption
capacity from the soil of different sesame varieties. The minimal point of soil
moisture the plant requires not to wilt is defined as soil’s wilting coefficient. If
moisture decreases to this or any lower point a plant wilts and thus can no longer
recover its turgidity. The physical definition of the wilting point (symbolically
expressed as θ
pwp
or θ
wp
) is defined as the water content at −1500 J/kg (or −15 bars)
of suction pressure, or negative hydraulic head. The results are indicated in the Table
3.2.
For soil’s wilting coeficient, V5 and V14 were withered when water content in
soil was low, which was only 10.89% and 11.04% compared to undried soil. V3 and
V8 were withered when water content in soil was higher, reaching 14.92% and
15.08%, respectively.


3.1.1.3 Impacts of drought on water content in tissues
At diferent drought levels, water content in tissues is different between
varieties. Water content in tissues inffluences physical actitives in general and in leaf
tissues in particular. Therefore, the water content in plant at wilting point is critial for
Varieties
Humidity of
withered plant

Soil’s wilting
coefficient (g
H
2
O/100g dried soil)
Drought
tolerance
ranking
V1 11.29
a
3.54 a* 4
V2 13.34
b
4.25 b* 11
V3 15.08 f

4.85 e* 20
V4 14.37
c
4.61 c* 18
V5 10.89
d

4.31 b* 13
V16 12.07
i
3.81 f* 6
V17 11.32
a
3.55 a* 5
V18 13.45
b
4.29 b* 12
V19 12.11
i
3.83 f* 7
V20 14.16
h
4.53 b*c* 17
6

supplementary water for plants, minimizing harmful effects of drought on crops and
through this amount of water we can assess water dificit torelance capacity.
Table 3.3. Water content in leaf tissues when plant withered
Water content in tissue when plant withered (%)
Sesame
varietiesNormal
condition
Drought
condition

80.12 1
V6 83.03
c
69.91
c*
84.19 10
V7 82.67
a
70.69
a*
85.50 14
V8 81.03
e
70.26
a*
86.70 18
V9 81.74
c
70.13
a*
85.79 17
V10 81.53
e
67.27
e
82.50 4
V11 80.61
b
68.53
c*

81.76 3
V18 83.04
c
69.78
a*
84.03 9
V19 82.15
a
68.85
c*
83.81 7
V20 85.75
d
75.46
f
88.00 20
The data showed that: under impact of drought, water content in leaf tissues of
all varieties was reduced in comparison to normal condition. Water content in leaf
when plants were withered ranges from 80.12 to 88% in comparison with those of
insufficient water. Of which, water content in leaf tissue when plant withered was
lowest for V5 variety and was 80.12 (compared to this value when plant do not wilt).
This value is 81.46 for V14 variety. Water content in leaf tissue was the highest for
V20 variety (88.00%) and V3 variety (86.96%). At the wilting point, variety which
has lower water content in leaf tissue per water content at normal condition has
higher drought tolerance. That means V5, V14 varieties can resist to drought better
than V5, V20 varieties.
3.1.1.4. Impact of drought on associated water content in leaf
In the drought condition, water in plant has a trend to increase associated water
content and increase free water content. Therefore, associated water content and
water-retaining capacity of leaf tissue have very important meaning for tolerance

a*
162.16 15
V3 21.78
a
33.25
b*
152.66 20
V4 19.49
b
31.16
c*
159.87 17
V5 23.25
c
43.86
d
188.64 2
V6 20.03
a
33.91
b*
169.29 11
V7 22.53
a
39.27
e
174.30 7
V8 23.56
c
37.32

d
190.13 1
V15 19.17
b
34.12
b*
177.96 5
V16 20.56
a
36.24
a*
176.26 6
V17 21.03
a
38.26
e
181.93 3
V18 23.04
c
38.78
e
168.31 12
V19 22.15
a
37.85
a*
170.88 10
V20 23.46
c
36.16

Table 3.5. Water-retaining capacity of leaf tissue in drought condition of 20
researched sesame varieties
Water-retaining capacity of leaf tissue (% content of lost water/ total
water content)
Sesame
varieties

One day
after
drought
treatment
Drought
tolerance
ranking
Three days
after
drought
treatment
Drought
tolerance
ranking
Five days
after
drought
treatment
Drought
tolerance
ranking
V1 29.46
a

2 36.17
g
2
V6 26.87
b
7 18.95
b*
19 40.21
a**
13
V7 27.34
b
9 16.78
a*
10 40.15
a**
11
V8 33.14
c
20 17.41
b*
14 41.68
b**
18
V9 31.34
c
18 15.63
a*
4 40.01
a**

e
1 13.07
e*
1 35.69
h
1
V15 25.67
e
4 15.26
a*
3 38.62
f
4
V16 27.21
b
8 17.31
b*
13 39.67
d
8
V17 25.15
e
3 16.58
a*
9 37.04
e
3
V18 27.86
b
11 17.51

treatment days, or after five drought treatment days. Water-retaining capacity of leaf
of all researched varieties is reduced. At the same drought treatment period, the
varieties which have smaller content of lost water/ total water content will have better
water-retaining capacity.
Collected data illustrated that: at three point of time, after 1, 3 and five drought
treatment days, content of lost water is the smallest for V14 variety; following is V5
meaning that these two varieties have the best water-retaining capacity.
The group, which has the worst water-retaining capacity, does not identically
fluctuate. In particular: after one drought treatment day, position of ranking order 20
belongs to V8; after three drought treatment days this position belongs to V20; and
after five drought treatment days is V3. Therefore, it is clear that all three varieties
V3, V8, and V20 belong to groups, which have the worst water-retaining capacity or
the lowest drought tolerance.
Together with relative drought tolerance capacity, the water-retaining capacity
of leaf tissue also has similar results for some groups such as: V5, V14 which have
the highest water-retaining capacity while V3, V8, V20 have the worst water-
retaining capacity.
3.1.1.6. Impacts of drought on content of chlorophyll and fluorescent chlorophyll
of sesame leaf
In the drought condition, then content of chlorophyll is different in each
variety. The indicator of chlorophyll content, especially the content of relative
pigments can be used to evaluate photosynthesis activity and resistance capacity of
crop. We calculated content of total chlorophyll and content of relative chlorophyll of
20 researched sesame varieties and realized that:
The content of total chlorophyll of all 20 sesame varieties is reduced when
drought occurs. The two varieties V5 and V14 reaches the highest value of
chlorophyll content (1.934 mg/g leaf and 1.930 mg/g leaf). These two varieties are
also slightly impacted by water deficit (reached 90.53% and 88.44% in comparison to
the normal condition). Therefore, they rank the first and the second position
respectively. V3 and V13 are the most seriously influenced by water deficit, which


11Changing of relative chlorophyll level is related to changing of relative
chlorophyll a and b level. Experimental results proved that relative chlorophyll level
is reduced in drought condition and varies in different sesame varieties, which
reached from 70.00 to 90.00% as compared with the normal condition. Varieties V5
and V14 have clearly higher content of relative chlorophyll level a+b than the
remaining varieties (1.01 mg/g and 1.00mg/g), chlorophyll level of these two
varieties in drought condition also change less than other varieties. Relative
chlorophyll level a+b is remarkably reduced when water deficit condition occurs for
V3 and V4 (70.00% and 73.68%).

In chloroplast, chlorophyll closely relates to protein and lipid to create a

vm
means that PSII’s activity decreases leading to the decrease of
using effectiveness of energy in photosynthesis.
Based on the indicator of the fluorescent chlorophyll level, it can be affirmed
that: drought resistant capacity of V5 and V14 are the highest; V3 and V8 have the
lowest drought tolerance.
Many researches indicated that: the impact of drought and water deficit on
developing tissue leads to inhibit photosynthesis. In detail, when water deficit occurs,
plants react with quick closing stoma to reduce water loss. At the same time, reduced
CO
2
diffusion into leaf also leads to the decreased absorption CO
2
of ribulose1,5
diphosphate and impact on photosynthesis effectiveness. Drought can have direct
impact on activity of ribulose 1,5 diphosphates cacboxylase enzyme /oxygenate, or
ATP synthesize. Photosynthesis electron which transports through PSII also is
inhibited. These are causes of declining using effectiveness of energy in
photosynthesis in PSII and reducing of photosynthesis effectiveness.
12

3.1.1.7. Impacts of drought on osmotic pressure.
Capacity of osmotic presure adjusment to balance water between cell and
surrounding environment is a critical quality and also is water deficit adaptable
measurement of many varieties.
When soil is dry, osmotic pressure of soil-liquid is very high so crops need to
adjust their osmotic pressure to be higher soil-liquid’s osmotic pressure to obtain a
little water remained in the soil.
Therefore, osmotic pressure determaination has critical meaning in evaluation
of water absorption capacity and holding-water capacity of crops. Osmotic pressure

V6 1.11 3.24 291.89 6
V7 1.23
c
3.08
c*
250.40 19
V8 1.20 3.17 264.16 17
V9 1.08 3.04 281.48 12
V10 1.12
d
3.39
d*
302.67 4
V11 1.07 2.90 271.02 13
V12 1.29 3.70 286.82 7
V13 1.25 3.38 270.40 14
V14 1.14
e
3.58
e*
314.03 1
V15 1.06 3.02 284.90 10
V16 1.03 2.92 283.49 11
V17 1.16
f
3.52
f*
303.44 3
V18 0.94 2.77 294.68 5
V19 1.01 2.69 266.33 15

with protein and lipid in cell membrane to prevent cell membrane from destroying.
In summary, one of factors has impact on osmotic pressure, water absorption
capacity and holding-water capacity of cells is the dissolved saccharoses, proline
amino acid. Clearly, there are relationships between two these factors and cells’
osmotic pressure, and crops’ drought tolerance capacity. This relationship would be
more clearly discussed in following indicators.
Determination of crops’ drought tolerance capacity does not only depend on
water exchange indicators but they also are results of many other factors. Therefore,
it is necessary to analyse biochemical indicators to determinate crops’ drought
tolerance in general and sesame’s drought tolerance in particular.
3.1.2. Impact of drought on biochemical indexes
3.1.2.1. Evaluation of drought tolerance through deoxidized saccharose level in
sesame’s leaf
Saccharose has an important role in life such as structure, energy providing,
especially saccharose play a critical role in osmotic pressure adjustment in cell liquid.
This is an advantage when crops deal with unfavourable conditions. Many researches
reveal that in unfavourable conditions such as heat, cold weather, drought …
saccharose level has a trend to increase. Therefore, it is needed to study changing of
saccharose level to find relationship between this level and crops’ resistance capacity.
The rate of sacchorase in drought and normal condition is presented in table 3.10.
Collected data in the table 3.10 reveal that all 20 sesame varieties have a trend
to increase saccharose level after drought treatment. Variety reaching the highest
increase of saccharose level is V14 (327.10%); following is V5 (309.52%); the
lowest level are V3 and V8, reaching 175.10% and 178.04%, respectively (lower than
14

other remaining varieties). In the drought condition, under influence of hydrolysis
enzyme, dispersion process of some organic substances such as protein, hydrate
carbon increases.
In particular, amylase enzyme activity increased to hydrolyze starch into

V4 1.38 2.64 191.30 16
V5 1.05
b
3.25
b*
309.52 2
V6 1.38 2.82 204.34 14
V7 1.82 3.34 183.51 18
V8 1.76
c
3.09
c*
175.56 20
V9 1.17 2.76 235.89 10
V10 1.09
d
3.08
d*
282.56 4
V11 1.51 3.71 245.69 9
V12 1.23 2.51 204.06 15
V13 1.19 3.16 265.54 7
V14 1.07
e
3.50
e*
327.10 1
V15 1.12 2.42 216.07 13
V16 1.21 3.43 283.47 3
V17 1.01 2.21 218.81 12

condition (%)
Drought
tolerance
ranking
V1 0.115 0.331 287.82 13
V2 0.128 0.385 300.78 7
V3 0.113
a
0.287
a*
253.98 20
V4 0.118 0.320 271.18 15
V5 0.152
b
0.503
b*
330.92 2
V6 0.149 0.481 322.81 4
V7 0.121 0.318 262.80 17
V8 0.109
c
0.283
c*
259.63 19
V9 0.120 0.354 295.00 11
V10 0.143
d
0.468
d*
327.27 3

reflection of plants in water deficit condition. Proline level in sesame leaves at the
seedling stage in normal and drought condition is compared in table 3.12.
Table 3.12. Proline level in sesame leaves in normal and drought condition
(increased percentage increase or number of times increases as compared with
drought condition)
Proline (µ
µµ
µmol/mg)
Sesame
varieti
es

Normal
conditio
n
Droug
ht
toleran
ce level

One day
after
drought
treatment
Drough
t
toleran
ce level

Two days

V5 0.341
a
1 0.663
a*
1 0.962
a**
1 1.254
a***
1
V6 0.323 3 0.552 3 0.864 8 1.116 5
V7 0.271 13 0.494 8 0.803 14 0.954 16
V8 0.198
b
20 0.347
b*
20 0.654
b**
20 0.856
b***
20
V9 0.298 5 0.485 10 0.904 3 1.043 10
V10 0.285
c
10 0.512 6 0.879 5 1.057 7
V11 0.267 14 0.478 12 0.802 15 1.123 4
V12 0.253 17 0.502 7 0.835 9 1.056 8
V13 0.267 15 0.423 15 0.827 11 1.102 6
V14 0.328
a
2 0.635

0.663, 0.962 and 1.254 µmol/mg at one day, two days and three days after drought
treatment respectively. V14’s proline level also increases higher than other varieties
(V14’s level increase is lower than only V5) for all control experiments, at all periods
of time. At one, two and three days after drought treatment, this indicator increases
by 1.93 times, 2.78 times, 3.79 times as compared to normal condition, respectively.
In conclusion, depending on leaf’s proline level group, which has the highest
ptoline level at different period of drought treatment, correlates to the best drought
tolerance capacity including V5 (the first position ranking) and V14 (the second
position ranking).
V8 has the lowest proline at all drought treatment periods (in normal condition
was 0.198 µmol/mg, one day after drought treatment reaches 0.347µmol/mg, two
days after drought treatment reaches 0.654 µmol/mg and three days after drought
treatment was 0.856µmol/mg). Following is V20, which have proline level higher
than only V8 at three situations: normal condition and two days after drought
treatment.
If based on proline level, low drought capacity group (correlated to the lowest
proline level at different periods of drought treatment) includes three varieties, which
are categorized gradually reduced proline level are V4, V20 and V8.
Proline level parameter also correlates to cell’s osmotic pressure, which is
presented in previous section (table 3.9).
3.1.3. General evaluation of drought tolerance capacity and biophysical,
biochemical indicators
Based on researched biophysical and biochemical indicators, we evaluated
twenty sesame varieties’ drought tolerance on a basis of appearance frequency at
ranking position from the first position to 20
th
position (in table 3.13).
Results in table 3.13 proved that: two varieties V14 and V5 always take place at the
first and second position following drought tolerance ranking. It is followed by
varieties V10, V17. Two varieties V3, V8 frequently appear at 19
19

3.2. Studied results of genetic polymorphism analysis of twenty sesame varieties
The phylogenetic tree generated from RAPD data indicates


Diagram 3.8. The polygenetic tree diagram on genetic relationship of twenty
researched sesame varieties. Numbers in diagram are correlative
in order in table 2.1
II
III
I
Nhóm 2
Nhóm 1
20

Group 1 consists of 15 varieties which are split into 3 subgroups (at 65% genetic
similarities): subgroup 1 has variety No.1; the subgroup 2 includes 6 varieties: variety
No.2, 16, 9, 11, 13, 18; the subgroup 3 includes 8 varieties: variety No. 6, 17, 19, 10,
12, 14, 15. The group 2 consists of the rest 5 varieties: variety No. 3, 4, 7, 8, 20.
3.3. Evaluation of productivity and quality of six sesame varieties
3.3.1. Productivity
We determined above indicators of 6 varieties, which were considered having
the best, medium and the lowest drought tolerance capacity, based on numbers of
fruits per tree, number of firmed seeds per fruit, and quantity of 1000 seeds.
Table 3.15. Factors forming productivity and net productivities of the six
researched sesame varieties
Order


3 V8 31.3
a
84.7
a
2.365
a
15.29
a

4 V10 33.2
a
87.4
a
2.558
c
16.25
c

5 V14 36.1
b
97.8
b
2.894
b
18.15
b

6 V17 28.2
a
86.5

Table 3.16. Lipid content and lipid indexes in sesame seed
Order

varieties

Lipid
content
(%)
Lipid
indexes
Soap
indexes
Iodine
indexes
1 V3 47.14
a
3.36
a*
65.8
a**
130.2
a***

2 V5 53.32
b
2.64
c*
64.3
a**
131.9

bc
2.85
a*b*
60.7
a**
135.3
a***

Fatty acid composition was most concerned among above analyzed lipid
indexes. This is also standards to evaluate sesame quality and maintaining
measurement. This index is lower, sesame quality is better, sesame is easier to
maintain and does not need complicated process. All three sesame varieties, which
had high fatty acid composition (V5, V14, V17), had acid index lower than 3. V3
variety had the highest acid index (3.36), this is also low drought tolerance variety
and V3’s fat content and acid index do not fulfill export requirements of fat content
and acid index. These indexes of two sesame varieties V8 and V10 were 3.24 and
3.02, respectively.
3.3.3. Fatty acid composition in sesame seed
Unsaturated fatty acids help crops absorb better, presence of these unsaturated
fatty acids enhance sesame oil quality in particular and plant oil in general. We
analyzed content of five main fatty acids to determine the role of these acids in
sesame seeds. Gained results are presented in table 3.17.
Table 3.17. Fatty acid composition in sesame seeds
Fatty acid compositions (%) Order

Varieties

Plasmatic

Stearic

3.98
d
39.45
a
32.53
b

0.44
c

4 V10 6.28
e
3.95
d
40.33
a
33.70
b

0.54
c

5 V14 5.79
e
4.21
d
39.78
a
33.29
b