Title Page

Contents

Ⅰ. Introduction 10

Ⅱ. Literature Reviews 14

1. Causes and effects of drought stress on plants 14

2. Growth responses to drought 17

3. Morpho-anatomical responses to drought 17

4. Physiological responses to drought 19

5. Biochemical responses to drought 21

Ⅲ. Materials and Methods 24

1. Study area 24

2. Plant materials and experimental design 25

3. Measurement of growth parameters 29

4. Measurement of morpho-anatomical parameters 29

5. Measurement of physiological parameters 31

6. Measurement of biochemical parameters 32

7. Data and statistical analysis 33

Ⅳ. Results 34

1. Growth performance of the three species between treatments 34

2. Morpho-anatomical responses of the three species to water stress 36

3. Physiological response of the three species to water stress 44

4. Biochemical response of the three species to water stress 48

5. Principal component biplot analysis 49

Ⅴ. Discussion 53

1. Growth, morpho-anatomical, physiological, and biochemical responses of the three species to progressive water stress 53

1.1. Growth 53

1.2. Morpho-anatomy 54

1.3. Physiological 58

1.4. Biochemical 59

2. Water stress resistance strategies of Quercus acutissima, Quercus serrata, and Betula schmidtii 60

Ⅵ. Conclusion 67

Ⅶ. References 69

Abstract 83

Table 1. Average initial stem diameter (SD) and height (HT) growth of Quercus acutissima, Quercus serrata, and Betula schmidtii. 25

Table 2. List of growth, morpho-anatomical, physiological, and biochemical variables measured in the study. 28

Table 3. Specific leaf area (SLA) and leaf thickness (Lₜ) in WW (well-watered) and WS (water-stressed) seedlings of Quercus acutissima, Quercus serrata,... 38

Table 4. Leaf relative water content (RWC) of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-stressed) treatments. 47

Figure 1. Schematic diagram of the adverse effects and response mechanism of plants to drought stress. 16

Figure 2. Monthly mean temperature and relative humidity in the greenhouse during the study period (May-September 2020). 24

Figure 3. (a) Experimental setup in the greenhouse (b) soil volumetric water content sensors installed in the two pots of each water stress treatment. 26

Figure 4. Weekly soil volumetric water content of WW (well-watered) and WS (water-stressed) pots containing the seedlings of Quercus acutissima,... 27

Figure 5. Stem diameter and height of Quercus acutissima, Quercus serratci, and Betula schmidtii in WW (well-watered) and WS (water-stressed)... 35

Figure 6. Biomass growth of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-stressed) treatments.... 36

Figure 7. Stomatal pore area (㎛) of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-stressed)... 39

Figure 8. Representative stomata samples of Quercus acutissima. Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-stressed)... 40

Figure 9. Frequency distribution of fine root xylem vessel diameter classes of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW... 41

Figure 10. Representative xylem vessels of fine roots of Quercus acutissima (a-d), Quercus serrata (e-h), and Betula schmidtii (i-l) in WW (well-watered)... 42

Figure 11. Tyloses frequency in root tracheary cells of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-... 43

Figure 12. Representative tylosis in fine root tracheary cells of Quercus acutissima. Quercus serrata, and Betula schmidtii subjected to WW (well-... 44

Figure 13. Photosynthesis rate (AN), sub-stomatal CO₂ concentration (Ci), and stomatal conductance (gs) of Quercus acutissima, Quercus serrata, and Betula...[이미지참조] 46

Figure 14. Total soluble sugars (TSS) of Quercus acutissima, Quercus serrata, and Betula schmidtii in WW (well-watered) and WS (water-stressed)... 48

Figure 15. Principal component (PC) loading plot of growth, morpho-anatomical, physiological, and biochemical variables observed from Quercus... 50

Figure 16. Principal component (PC) loading plot of growth, morpho-anatomical, physiological, and biochemical variables observed from Quercus... 51

Figure 17. Principal component (PC) loading plot of growth, morpho-anatomical, physiological, and biochemical variables observed from Betula... 52