Plant growth, development and differentiation ( 6 hr)

1. Plant growth, development and differentiation (6 hr) • - Plant growth and development • - Plant cell differentiation • - Plant hormones and their controls in plant development • - Control of flowering

2. Stress relaxation of cell wall Cosgrove D.J. 1997. Plant Cell 9: 1031-1041

3. Acid growth theory Growth hormone auxin induces elongation growth of plant cells. -IAA +IAA Growing cell wall extend much faster at acidic pH than at neutral pH. Auxin-induced growth is associated with wall acidification.

4. Acid growth theory Hager A. et al. 1991 Planta 185: 527-537

7. Evidences supporting the Acid Growth Theory (a) stem and coleoptile sections excrete protons in response to auxin, lowering the pH of the apoplast. (b) treatment of auxin-sensitive tissues with acidic buffers of pH 5.0 can cause cells to elongate at rates comparable to that induced by auxin. (c) neutral buffers infiltrated into the apoplast can inhibit auxin-induced growth. (d) the fungal toxin fusicoccin, whose main action is to promote extensive acidification of the apoplast, also causes rapid cell elongation.

8. Growth curve “unicellular organism” Figure 1   Growth of the unicellular green alga Chlamydomonas. Growth is assessed by a count of the number of cells per milliliter at increasing times after the cells are placed in fresh growth medium. Temperature, light, and nutrients provided are optimal for growth. An initial lag period during which cells may synthesize enzymes required for rapid growth is followed by a period in which cell number increases exponentially. This period of rapid growth is followed by a period of slowing growth in which the cell number increases linearly. Then comes the stationary phase, in which the cell number remains constant or even declines as nutrients are exhausted from the medium.

9. Growth curve “multicellular organism” วัดการเติบโตจาก - น้ำหนักสด - น้ำหนักแห้ง - ปริมาตร - ความสูง - ฯลฯ ที่ระยะเวลาต่าง ๆ Shoot dry weight(kg)

10. inflorescence • Reproductive development • การเข้าสู่ระยะเจริญพันธุ์ (reproductive stage) ควบคุมโดยปัจจัยสิ่งแวดล้อม เช่น อุณหภูมิและจำนวนชั่วโมงแสง • เนื้อเยื่อเกิดการเจริญเป็น floral meristem

11. ทำอย่างไร พืชจะออกดอก

12. “ทำอย่างไร พืชจะออกดอก” tropical/ temperate sun /shade plant annual/ perennial ๑. รู้จักธรรมชาติของพืชต้นนั้น etc. ๒. เข้าใจกลไกควบคุมการออกดอก signal/ receptor/ gene expression

13. ทบทวนโครงสร้างดอก

14. เนื้อเยื่อเจริญ: floral meristem โครงสร้างของดอก ชั้นของดอก (whorl) 4 ชั้น

15. Flowering genes

16. ABC model: three floral organ identity genes Homeotic mutation

18. Flowering signals and receptors

19. Photoperiod: day length controls of flowering Long-day plants Short-day plants

20. Phytochrome control of flowering

21. Vernalization: cold promotes flowering

22. Four developmental pathway for flowering Taiz and Zeiger (2002)

23. เข้าใจกลไกควบคุมการออกดอกเข้าใจกลไกควบคุมการออกดอก signal ภายใน: hormone (gibberellins), circadian rhythm (physiological clock) ภายนอก: light, temperature, humidity, nutrient receptor phytochrome (light); ? (temperature) gene expression meristem identity genes/ floral organ identity genes/ cadastral genes