Effect on growth of cucumber seedlings at low temperature

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY NGUYEN HA TRANG EFFECT ON GROWTH OF CUCUMBER SEEDLING AT LOW TEMPERATURE BACHELOR THESIS Study mode: Full-time Major: Environmental Science and Management Faculty: Advanced Education Program Office Batch: 2014 - 2018 Thai Nguyen, 16/08/2018 Thai Nguyen University Of Agriculture And Forestry Degree Program: Bachelor of Environmental Science and Management Student name: Nguyen Ha Trang Student ID: DTN 1454290033 Thesis Title: EFFECT ON GROWTH OF CUCUMBER SEEDLINGS AT LOW TEMPERATURE Supervisor (s): Dr Duong Van Thao, Thai Nguyen University of Agriculture and Forestry Assist Professor San-Gwang Hwang, National Chung Hsing University, Taiwan Supervisor’s signature Abstract: Low temperature stresses are major environmental limiters for horticultural production in greenhouses in Taiwan during winter period The exposure of tropical and subtropical plants such as cucumber (Cucumis sativus L.) to low temperatures constitutes a severe limitation to their seedling establishment, physiology and production In this study, six cucumber cultivars (CU-87, CU-127, Cuigu, Kappa i summer no.7, Kappa summer no.11, CU-74) were cultivated from seed to the seedlings which have two true leaves for testing in control conditions (25/18˚C, day/night), chilling treatment (7/4˚C, day/night) and upon re-warming to (25/18˚C, day/night) In this study, series of experiments about cucumber seedlings treated with low temperature were tested to see whether their chilling tolerance would be significantly affected; and compare the effects of a cold treatment on membrane integrity of six cucumber cultivars and their recovery The results showed that cucumbers were sensitive to chilling stresses, which made the leaves wither in some cucumber seedlings and inhibited cucumber growth in this study Finally, Kappa summer no.7 exhibited as the highest cold resistance cultivar which is suitable for using in winter weather Key-words: Low temperature, cucumber cultivars, cucumber seedling, Kappa summer no.7, cold resistance Number of pages: 39 Date of submission: 16/08/2018 ii ACKNOWLEDGEMENT I would like to acknowledge everyone who played a role in my academic accomplishments First of all, I would like to emphasize the sincere appreciation to my university - Thai Nguyen University of Agricultural and Forestry which gave me a chance to my thesis abroad The internship opportunity I had with Horticulture Department- National Chung Hsing University was a great chance for learning and experiencing Therefore, I consider myself as a very lucky individual as I was provided with an opportunity to be a part of it I would like to express my deep and sincere gratitude to Prof San Gwang Hwang for the continuous support of my internship study and research He always helped me any time and also gave me the best conditions, supported all materials for my research and discussed any problems I got whenever I did experiment in his Vegetable laboratory Special thanks must go to Dr Duong Van Thao who always supported and cheered me up whole the time He gave me valuable and constructive comments on the manuscript and helped me to increase the quality of the thesis I wish to express my sincere thanks to Wayne Shih- a master student who helped me a lot for my experiment during the time I worked with him Without his assistance and dedicated involvement in every step throughout the process, this paper would have never been accomplished I would like to thank the lab mates for their help and sharing during the time I worked at the Vegetable laboratory My thankfulness would also send to my friends iii who have been studying in NCHU for their sharing to overcome all obstructs in the study-time, we have had useful discussions for my research Finally I deeply thank my parents, who supported me with love and understanding It was their love that raised me up again when I got weary Without you, I could never have reached this current level of success Sincerely, Nguyen Ha Trang iv TABLE OF CONTENT LIST OF FIGURES vii LIST OF TABLES viii LIST OF ABBREVIATIONS ix PART I INTRODUCTION 1.1 Research rationale .1 1.2 Research’s objectives 1.3 Research questions and hypotheses 1.4 Limitations 1.5 Definitions PART II LITERATURE REVIEW 2.1 An overview about six cucumber cultivars .6 2.2 Effect of chilling on the physiological processes in chilling-sensitive plants 2.3 Cell membrane changes .9 PART III METHODS 12 3.1 List of instruments 12 3.2 List of chemicals 12 3.3 Materials 14 3.4 Plant growth and conditions 14 3.5 Experimental design 15 3.5.1 Change of chlorophyll fluorescence .15 3.5.2 Cold injury symptom 16 3.5.3 Leaf electrolyte leakage 16 v 3.5.4 MDA content measurement 17 3.6 Statistical analysis 18 PART IV RESULTS 19 4.1 Chlorophyll fluorescence (Fv/Fm) 19 4.2 Severity of chilling injury 23 4.3 Leaf electrolyte leakage 28 4.4 Malondialdehyde .29 PART V DISCUSSION AND CONCLUSION 31 REFERENCES 34 vi LIST OF FIGURES Figure 4.1 Chlorophyll fluorescence of cultivars of cucumber under control 19 Figure 4.2 Chlorophyll fluorescence of cultivars of cucumber under days chilling 20 Figure 4.3 Relative reductions of chlorophyll fluorescence (%) under days chilling 22 Figure 4.4 Relative recovery of chlorophyll fluorescence (%) after days chilling .23 Figure 4.5 Five levels severity of cold injury of the leaves 25 Figure 4.6 Control group at (a) day 0, (b) recovery day .26 Figure 4.7 The chilling group at (a) day 0, (b) recovery day .27 Figure 4.8 The severity of chilling injury between first leaf and second leaf of six cultivars of chilling group .27 Figure 4.9 Leaf electrolyte leakage (%) of cucumber cultivars under chilling 29 Figure 4.10 Malondialdehyde (nmol g/FW) of cucumber cultivars under chilling 30 vii LIST OF TABLES Table 2.1 List of vegetables, sensitive to chilling temperatures, the lowest safe storage temperature and the symptoms of chilling injury Table 2.2 Six cucumber cultivars information .7 Table 3.1 Name and commercial company of all instruments used in this study 12 Table 3.2 Properties of liquid nitrogen 12 Table 3.3 Properties of trichloroacetic acid 13 Table 3.4 Properties of thiobarbituric acid 13 Table 3.5 Six cucumber cultivars 14 Table 3.6 Appearance severity level of cold damage 16 Table 4.1 Data of reduction and recovery of chlorophyll fluorescence (%) of chilling group 21 viii LIST OF ABBREVIATIONS CI Chilling injury EC Electrical Conductivity Fv/Fm Chlorophyll fluorescence maximal quantum efficiency of PSII MDA Malondialdehyde PSI Photosystem I PSII Photosystem II ROS Reactive oxygen species SCI Severity of cold injury ix Figure 4.5 Five levels severity of cold injury of the leaves (a) The control group at day 25 (b) The control group at recovery day Figure 4.6 Control group at (a) day 0, (b) recovery day (a) The chilling group at day 26 (b) The chilling group at recovery day Figure 4.7 The chilling group at (a) day 0, (b) recovery day Severity of chilling injury Severity of chilling injury score a First true leaf a Second true leaf a bc b bcd b cd d b b b CU87 CU127 Cuigu Kappa summer Kappa summer no no 11 Cultivar CU-74 Figure 4.8 The severity of chilling injury between first leaf and second leaf of cultivars of chilling group; Vertical bars represent the standard deviation of the mean Different letter indicate the significant differences between cultivar at P