QUA TRINH RA HOA THUC VAT (FLOWER)

Flower: evidence for signal transduction Flower inducement by photoperiodism Organ and molecule perceive photoperiod General structure of the flower How are the female and male gamerophytes produced? Flower, Fruit and seed Flower: develop from a compressed stem and highly modified leaves When What Photoperiodism: any response by an organism that is based on photoperiod Photoperiodism Short-day plant: blooming in spring, late summer or fall: • only flowering if days are shorter than critical day length • Asters, chrysanthemums, poinsettias… Long-day plant: bloom in midsummer, when days are longest and nights shortest: • flowering only when days are longer than a critical day length • Radishes, spinach, lettuce, and many cereal… Day – neutral plant: flowering without the regard to photoperiod: • Day length has no effect on flowering • Roses, snapdragon, tomatoes, cucumber, and many weed Light or darkness period is the controlling factor in flowering A 16 (8) B (16) Short-day plant: Critical duration light < 8,5hs C (14) D (8) E 16 (32) F 16 (12) G 15 (9) H (9) Long-day plant Critical duration light > 8,5hs Critical night length Night breaks can cancel the effect of dark period Short-day plant (long-night plant) Long-day plant (short-night plant) Experiment on short – night plant Question: Can signals from single leaf induce flowering? Hypothesis: signals from single leaf can induce flowering Null hypothesis: signals from single leaf can not induce flowering Experimental setup Expose only this leaf to short-night photoperiod Predict: plant will flower Predict of null hypothesis: plant will not flower Result plant flowers Plant expose long-night photoperiod Conclusion: a signal from single leaf can induce flowering Experiment on grafting leaf to short-night plant Predict: plant will flower Question: Can signals from different plant induce flowering? Predict of null hypothesis: plant Hypothesis: signals from grafted leaf can induce flowering Null hypothesis: signals from grafted leaf can not induce flowering Experimental setup will not flower Result plant flowers New plant expose to long-night photoperiod graft Leaf expose to short-night photoperiod Conclusion: a signal from single leaf can induce flowering Experiment on grafting leaf to long -night plant Phytochrome is primary photoreceptor in photoperiodism Interconversion of Phytochrome Effect of red light and far-red light Effect of red light and far-red light General structure of the flower Flowers diversity carpel petal sepal sepal petal carpel stamen stamen sepal • Sepal form an outer, protective whorl petal • Petal furnish a visual advertisment Carpels produce ovules Stamens produce pollen Male and female flowers can occur on the same or on different individual male flowers Female flowers Formation of female gametophyte The megasporocyte inside the ovule undergoes meiosis, resulting in four megaspores (2n) meiosis Three of megaspores degenerate (n) mitosis The surviving divides by mitosis to form haploid nuclei and arrange The cell wall form to yield cells Formation of male gametophyte (2n) meiosis (n) mitosis Many microsporocytes reside inside the anther A microsporocytes divide by meiosis, resulting in four microspores Each microspores divides once by mitosis, forming the tube cell and generative cell The resulting cell mature into a single pollen grain containing an immature male gametophyte The generative cell will later divide to form sperm nuclei [...]... megaspores degenerate (n) mitosis 3 The surviving divides by mitosis to form 8 haploid nuclei and arrange The cell wall form to yield 7 cells Formation of male gametophyte (2n) meiosis (n) mitosis 1 Many microsporocytes reside inside the anther A microsporocytes divide by meiosis, resulting in four microspores 2 Each microspores divides once by mitosis, forming the tube cell and generative cell 3 The... meiosis, resulting in four microspores 2 Each microspores divides once by mitosis, forming the tube cell and generative cell 3 The 2 resulting cell mature into a single pollen grain containing an immature male gametophyte The generative cell will later divide to form sperm nuclei ...Phytochrome is primary photoreceptor in photoperiodism Interconversion of Phytochrome Effect of red light and far-red light Effect of red light and far-red light General structure of the flower Flowers diversity carpel petal sepal sepal petal carpel stamen stamen sepal • Sepal form an outer, protective whorl petal • Petal furnish a visual advertisment Carpels produce