声明
Table of contents
摘要
ABSTRACT
CHAPTER 1：REVIEW OF LITERATURE
1．1．Background
1．2．Effects of drought stress on plants
1．2．1．Crop growth and yield
1．2．2．Plant-water relations
1．2．3．Photosynthetic limitations
1．2．4．Stomatal oscillations
1．2．5．Oxidative damage
1．2．6．Assimilate partitioning
1．3．Plants’ adaptation mechanisms to drought stress
1．3．1．Morphological adaptation mechanisms
1．3．2．Physiological adaptation mechanisms
1．4．Effects of post-anthesis drought stress on grain formation
1．4．1．Effects on growth hormones levels and grain size development
1．4．2．Effects on carbohydrate metabolism enzyme activities and grain filling
1．5．Response of pre-drought experienced plant to post-anthesis drought conditions
1．6．Objectives of study
1．7．Technical rout map of study
References
CHAPTER 2：EFFECTS OF WATER DEFICITS APPLIED DURING VEGETATIVE GROWTH STAGES ON POST-ANTHESIS PHOTOSYNTHESIS，DRY MATTER RE-MOBILIZATION，GRAIN YIELD，AND WATER UTILIZATION IN WHEAT
2．1．Introduction
2．2．Materials and methods
2．2．1．Plant culture and growth conditions
2．2．2．Water deficit treatments application and management
2．2．3．Determination of amount of water applied
2．2．4．Plant sampling and harvesting
2．2．5．Traits measurements
2．2．6．Leaf chlorophyll contents
2．2．7．Leaf morphological traits
2．2．8．Photosynthetic measurements
2．2．11．Mobilization of pre-anthesis accumulated dry matter contents
2．2．12．Water use efficiency and water productivity
2．3．Statistical Analysis
2．4．Resuits
2．4．1．Amount of water applied
2．4．2．Leaf chlorophyll contents
2．4．3．Leaf area
2．4．4．Leaf thickness
2．4．5．Effects of water deficits on post-anthesis photosynthetic rate
2．4．6．Grain filling duration，grain yields and harvest index
2．4．7．Number of spikes，grains per spike，and 1000-grain weight
2．4．8．Pre-anthesis dry matter production and pre-deficit limitation
2．4．9．Pre-anthesis dry matter mobilization efficiency and contribution to grain yield
2．4．10．Water use efficiency and water productivitv
2．5．Discussion
2．6．Conclusions
References
CHAPTER 3：ADAPTATION TO AND RECOVERY FROM DROUGHT STRESS AT VEGETATIVE STAGES IN WHEAT CULTIVARS
3．1．Introduction
3．2．Materials and methods
3．2．1．Plant culture and growth conditions
3．2．2．Plant sampling and traits measurement
3．2．3．Leaf water relations and membrane stability index measurements
3．2．4．Leaf gas exchange measurements
3．2．5．Chlorophyll fluorescence measurements
3．2．6．Chlorophyll contents and morphological leaf traits measurements
3．2．7．Relative growth rate and dry matter determinations
3．2．8．Determination of reactive oxygen species，lipid peroxidation andenzymatic antioxidant activities
3．2．9．Determination of non-enzymatic antioxidants
3．2．10．Determination of carbohydrates，free amino acids and proline
3．3．Statistical analysis
3．4．Resuits
3．4．1．Changes in membrane stability index and membrane injury
3．4．2．Leaf gas exchange parameters
3．4．3．Chlorophyll fluorescence parameters
3．4．4．Leaf traits
3．4．5．Relative growth rate and dry matter production
3．4．6．Changes in reactive oxygen species and MDA contents
3．4．7．Changes in enzymatic antioxidant activities
3．4．8．Changes in non-enzymatic antioxidants
3．4．9．Changes in soluble proteins，free amino acids and proline contents
3．4．10．Changes in carbohydrates
3．4．11．Changes in leaf water relations and osmotic adjustment
3．5．Discussion
3．6．Conclusions
References
CHAPTER 4：RESPONSE OF MODERATE PRE-DROUGHT EXPERIENCED PLANTS TO POST-ANTHESIS DROUGHT STRESS CONDITIONS
4．1．Introduction
4．2．Materials and methods
4．2．1．Plant culture and growth conditions
4．2．2．Drought priming treatments
4．2．3．Post-anthesis drought stress treatments
4．2．4．Plant sampling
4．2．4．Leaf water potential
4．2．5．Chlorophyll contents
4．2．6．Rubisco contents
4．2．7．Leaf gas exchange
4．2．8．Chlorophyll fluorescence
4．2．9．Enzymatic antioxidants activities
4．2．10．Lipid peroxidation estimation
4．2．11．Dry matte
4．2．12 Grain yield
4．2．13．Drought index
4．2．14．Harvest index
4．3．Statistical analysis
4．4．Results
4．4．1．Dry matter production
4．4．2．Grain yield production
4．4．3．Drought index
4．4．4．Harvest index
4．4．5．Leaf water potential
4．4．6．Chlorophyll and Rubisco contents
4．4．7．Leaf gas exchange and chlorophyll fluorescence
4．4．8．Lipid peroxidation and enzymatic antioxidant activities
4．5．Discussion
4．6．Conclusions
References
CHAPTER 5：EFFECT OF PRE-DROUGHT PRIMING ON PLANT GROWTH HORMONES AND GRAIN DEVELOPMENT REGULATION AGAINST POST-ANTHESIS DROUGHT STRESS
5．1．Introduction
5．2．Materials and methods
5．2．1．Plant culture and growth conditions
5．2．2．Drought priming treatments
5．2．3．Post-anthesis drought stress treatments
5．2．4．Plant sampling and harvesting
5．2．5．Leaf water potential
5．2．7．Leaf chlorophyll contents
5．2．9．Isolation and counting of endosperm cells
5．2．10．Grain size detection
5．2．11．Hormones extraction
5．2．12．Hormones quantification
5．3．Statistical analysis
5．4．Results
5．4．1．Changes in leaf water potential and chlorophyll contents
5．4．2．Changes in photosynthetic rate
5．4．3．Changes in endosperm cell number and cell division rate
5．4．4．Changes in grain size and moisture contents
5．4．5．Changes in grain filling rate and grain weight
5．4．6．Changes in grain filling duration and grain yield traits
5．4．7．Hormonal changes in grains
5．5．Discussion
5．6．Conclusions
References
CHAPTER 6：EFFECT OF PRE—DROUGHT PRIMING ON ENZYMES ACTIVITIES RELATED TO SUCROSE SYNTHESIS AND SUCROSE-TO-STARCH CONVERSION AGAINST POST-ANTHESIS DROUGHT STRESS
6．1．Introduction
6．2．Materials and methods
6．2．1．Plant culture and growth conditions
6．2．2．Plant sampling and harvesting
6．2．3．Water soluble carbohydrates contents
6．2．4．Amylose and amylopectin contents
6．2．5．Sucrose-metabolism enzymes extraction and assays
6．2．6．Sucrose synthase and invertase
6．2．8．Preparation，enzyme extraction and activity determination of sucrose-to-starch metabolism enzymes in grains
6．2．9．ADPGPPase activity
6．2．10．Sucrose synthase activity
6．2．11．SSS and GBSS activities
6．4．1．Changes in grain dry weight and stem dry weight
6．4．2．Changes in WSCs，sucrose and fructose content in stem
6．4．3．Changes in SS，SPS and INV enzyme activities
6．4．4．Changes in amylopectin and amylose contents and starch accumulation rate in grains
6．4．5．Changes in ADPGPPase，SS，SSS and GBSS enzyme activities
6．5．Discussion
6．6．Conclusions
References
CHAPTER 7：DISCUSSION AND CONCLUSIONS
7．1．Moderate water deficit at vegetative stages improved post-anthesis photosynthesis，dry matter re-mobilization，grain yield，and water utilization
7．2．Genotypic variations in adaptability to and recovery from drought stress are the indicators of drought tolerance
7．3．Osmotic adjustment and antioxidative changes during drought stress and re-watering periods at vegetative stages of wheat
7．4．Pre-drought priming triggers a faster and stronger defense mechanism against the subsequent post-anthesis drought stress
7．5．Pre-drought priming sustains grain filling process by modulating the synthesis of growth hormones against post-anthesis drought stress
7．6．Activities of sucrose synthesizing and sucrose-to-starch conversion enzymes in pre-drought primed against post-anthesis drought stress
7．7．Conclusions
7．8．New insights
7．9．Future recommendations
References
ACKNOWLEDGEMENTS
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