Effect of heat stress on the MDA, proline and soluble sugar content in leaf lettuce seedlings

doi:10.4236/as.2013.45B021

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Vol.4, No.5B, 112-115 (2013) Agricultural Sciences

doi:10.4236/as.2013.45B021

Effect of heat stress on the MDA, proline and soluble

sugar content in leaf lettuce seedlings

Yingyan Han, Shuangxi Fan*, Qiao Zhang, Yanan Wang

Department of Plant Science and Technology, Beijing Agricultural College, Beijing, China; *Corresponding Author: [email protected]

Received 2013

ABSTRACT

High temperature stress on different varieties of

lettuce seedlings in MDA, proline and soluble

sugar content were studied. The results w ere as

follows : With the stress temperature, varieties

of leaf lettuce seedlings in the MDA, proline and

soluble sugar content gradually increased; Dif-

ferent varieties had the most significant differ-

ence in 38/33℃ (d/n). The increase of heat-re-

sistant varieties on proline and soluble sugar

content was quick and high, while it s increas e in

MDA content was slow and small.

Keywords: Leaf Lettuce; High Temperature; MDA;

Praline; Soluble Sugar

1. INTRODUCTION

Leaf lettuce (Lactuca sative L.) native to the Mediter-

ranean coast liked the cold weather, and was prone to rot

species, seedling difficult, easy bolting, perishable and

other obstacles at high temperature, causing yield and

quality difficult to achieve the desired goal. Therefore,

fostering resistant varieties of leaf lettuce had to be re-

solved, and the problem of heat-resistant type of leaf

lettuce seedling formation and growth was an important

prerequisite for cultivating heat-resistant varieties. Cur-

rently more heat tolerance of vegetable was cabbage[1-3],

and the heat resistance of leaf lettuce on a rarely reported.

Study of this experiment in heat stress conditions, the

different varieties of leaf lettuce seedlings in the MDA,

proline and soluble sugar content, was designed to heat-

resistant varieties of leaf lettuce to provide a theoretical

basis.

2. TEXT

2.1. Material and Methods

2.1.1. Plant materials

There were significant differences in heat resistance of

four cultivars: S24, S39 for the heat-resistant varieties,

and J20, J2 is for the non-heat-resistant varieties.

2.1.2. High Temperature Treatments

When the seedlings to 4 or 5 leaves, when all varieties

of the same robust growth state selected plants, placed in

artificial climate boxes at 25/20℃ (d/n) (CK), 30/25℃

(d/n), 38/33℃ (d/n), 42/37℃ (d/n) for high temperature

treatment. Illumin ation period of 12 h/12 h (d/n), and air

humidity of (70 ± 5)%. To avoid the impact of drought,

the water treatment quantitative to maintain consistent

soil moisture. 10 seedlings per treatment were randomly

arranged. 3d after treatment were consistent with the

growth of leaves taken, immediately placed in liquid

nitrogen fixed -80℃ refrigerator.

2.1.3. The Content of MDA

The content of MDA was measured by thiobarbituric

acid colorimetry[4,5].

2.1.4. The Content of Proline

The content of proline was measured by sulfosalicylic

acid colorimetry[6].

2.1.5. The Content of Soluble Sugar

The content of soluble sugar was measured by an-

throne colorimetry[7] .

2.2. Results and Discussion

2.2.1. Effects of Heat Stress on MDA in Leaf

Lettuce Seedlings

Under stress conditions, MDA, as products of lipid

peroxidation, the level of its content was often used to

explain the extent of peroxidation. Figure 1 showed that

with increasing temperature, the content of MDA in-

creased. 30/25℃ (d/n), the content of MDA of S24 and

J20 increased slightly, but compared with the control, the

increase was not significant; The content of MDA of S39

and J2 was increased by 60.03% and 43.30%, to reach a

significant level. From this description, the content of

MDA of the non-heat-resistant varieties than the

heat-resistant varieties increased rapidly. 38/33℃ (d/n),

The content of MDA of S24 and S39 was increased by

50.70% and 97.49%, the MDA content of J20 and J2

increased 55.04% and 77.49% . Compared with control,

Y. Y. Han et al. / Agricultural Sciences 4 (2013) 112-115 113

species difference between the increase in MDA content

was significant, the increase of the content of MDA of

the heat-resistant varieties than the non-heat-resistant

varieties in small. The increase of the content of MDA

was related with varieties of heat resistance. 42/37℃

(d/n), all varieties were higher the content of MDA, but

compared with the control, varieties was no significant

difference between the content of MDA of increase.

2.2.2. Effects of Heat Stress on Proline in Leaf

Lettuce Seedlings

Proline as a kind of osmotic adjustment, under stress

the increase of proline content was benefit to stress in

plant resistance to a certain extent, enhancing the

adaptability of organisms to environmental stress. Figure

2 shows that with the temperature, the proline content of

the four kinds of leaf lettuce seedlings was rising. 30/25℃

(d/n), the proline con tent of S39 and J2 increased slightly,

but compared with the control, the increase was not sig-

nificant; the proline content of S24 and J20 was in-

creased by 27.01% and 22.40%, reached a significant

level. It showed the proline content of non-heat-resistant

varieties than heat-resistant varieties increased rapidly.

38/33℃ (d/n) , compared with the control, the increase

of proline of S24 w as 94.62%, S39 was 20.54%. J2 0 was

52.81%, and J2 was 13.82%, the most significant differ-

ence among varieties .42/37℃ (d/n), the proline content

of all varieties began to decrease, the increase of S24 and

J20 was significantly higher than the control, while the

S39 and J2 of the increase was not significant compared

with the control. These resu lts suggest that the content of

proline was related with varieties of heat resistance, the

heat-resistant varieties of proline content and growth

were higher.

2.2.3. Effects of Heat Stress on the Content of

Soluble Sugar in Leaf Lettuce Seedlings

Soluble sugar h elped reduce th e cell osmotic potential,

reduced water losses, and its role was important in re-

search of physiology. As can be seen from Figure 3, with

increasing temperature, leaf lettuce seedling soluble

sugar content increased significantly. 30/25℃ (d/n),

soluble sugar content of S24 and S39 was increased 1.68

times and 1.28 times, J20, and J2 was increased 1.43

times and 1.67 times. 38/33℃ (d/n), the peak of soluble

sugar content was reached. Compared with the control,

soluble sugar content of S24 and J20 respectively was

increased 2.48 times and 2.83 times, S39 and J2 was in-

creased 2.43 and 2.13 times respectively. Temperatures

continue to rise, the soluble sugar content of leaf lettuce

seedlings decreased slightly. These results indicated that

under heat stress, the soluble sugar content of leaf lettuce

increased, its content of heat-resistant varieties of seed-

lings higher than th e non-heat-resistant varieties.

0.00

100.00

200.00

300.00

400.00

500.00

600.00

25/20℃ 30/25℃38/33℃ 42/37℃

temperature

MDA

nmol/g

S24

S39

J20

Figure 1. Effects of heat stress on MDA in leaf lettuce seedlings.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

25/20℃ 30/25℃ 38/33℃ 42/37℃

temperature

PRO

ug/g

S24

S39

J20

Figure 2. Effects of heat stress on the content of proline in leaf lettuce seedlings.

Y. Y. Han et al. / Agricultural Sciences 4 (2013) 112-115

114

0.00

0.20

0.40

0.60

0.80

1.00

25/20℃ 30/25℃ 38/33℃ 42/37℃

temperature

soluble sugar

S24

S39

J20

Figure. 3. Effects of heat stress on the content of soluble sugar in leaf lettuce seedlings.

Many studies showed that the cell membrane more

sensitive to high temperature, was the core issues of h eat

damage and heat resistance of plant. Thylakoid mem-

brane and the plasma membrane than the mitochondria

were more susceptible to heat damage [8]. Heat stress

often leaded to oxidative stress, reactive oxygen species

(ROS) accumulation, Eventually leading to membrane

peroxidation, protein structure damage and DNA in-

jury[9-11]. MDA was a lipid peroxidation of product, its

content reflected the lev el of lipid levels by the injury. In

this study, with the temperature, the MDA content of leaf

lettuce of all varieties had increased, and high tempera-

ture stress on the non-heat-resistant varieties of mem-

brane stability was greater damage than the heat-resistant

varieties. This is Li Min[12] consistent with the findings

of the spinach.

However, the response of plants to heat stress was not

entirely passive, the body would occur through various

mechanisms and appropriate adaptive response to resis-

tance or to avoid harm to maintain basic metabolic pro c-

esses. Proline and soluble sugar to osmotic adjustment,

the increase of its concentration could increase the con-

centration of cell protoplasm, to maintain normal mem-

brane function at high temperatures to be conducive to

plant resistance of environmental stress, which could be

enhanced to some exten t the adaptability of organisms to

environmental stress. In this study, with the temperature,

leaf lettuce seedlings proline and soluble sugar content

increased, and the rate of increase in differences between

species, the heat-resistant varieties of increase was sig-

nificantly higher than the heat of the non-heat-resistant

varieties. The results were as the same as the proline

changes of tomato under high temperature stress [13].

But the soluble sugar content of eggplant was decreased

under high temperature [14], and Dioscorea zingibercnsis

leaves in the soluble sugar content showed a trend of

low-high-low level [15]. Results of this paper were not

agree with them and further studies are needs.

3. CONCLUSIONS

MDA con tent in radicles increased significantly as the

processing temperature rising, and the most obvious was

that in the range of 35 ℃- 40℃. The strong heat-resistant

varieties were lower of MDA than the weak

heat-resistant varieties. Theses show that membrane sys-

tem was hurt under the high-temperature, and the weak

heat-resistant varieties of destruction were more serious.

Activity of cell protective enzymes showed a downward

trend after the first rise, 30℃, all varieties of SOD and

POD activity reached a maximum; 35℃, the various

varieties of SOD and POD activity was significantly de-

creased, and there was the most significant difference

between varieties. The strong heat-resistant varieties of

these two protective enzyme activities were higher than

the weak heat-resistant varieties. Researches showed that

to maintain a high membrane protective enzyme activity

can reduce the heat hazards.

4. ACKNOWLEDGEMENTS

This work was supported by the earmarked fund for Beijing Leafy-

Vegetables Innovation Team of Modern Agro-industry Technology

Research System (Number blvt-02), the “Beijing Nova Program”

(Number 2010B020) and the “Beijing Natural Science Foundation”

(Number 6112005).

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