Transcript Growth Handout 2

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
Stress relaxation of cell wall
Cosgrove D.J. 1997. Plant Cell 9: 1031-1041
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.
Acid growth theory
Hager A. et al. 1991 Planta 185: 527-537
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.
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.
Growth curve
วัดการเติบโตจาก
- นา้ หนักสด
- นา้ หนักแห้ ง
- ปริมาตร
- ความสูง
- ฯลฯ
ที่ระยะเวลาต่ าง ๆ
Shoot dry weight (kg)
“multicellular organism”
inflorescence
Reproductive development
การเข้ าสูร่ ะยะเจริญพันธุ์ (reproductive stage)
ควบคุมโดยปั จจัยสิง่ แวดล้ อม เช่น อุณหภูมิและ
จานวนชัว่ โมงแสง
เนื ้อเยื่อเกิดการเจริญเป็ น floral meristem
ทาอย่ างไร พืชจะออกดอก
“ทาอย่ างไร พืชจะออกดอก”
annual/
perennial
tropical/
temperate
sun /shade
plant
๑. รู้ จักธรรมชาติของพืชต้ นนัน้
etc.
๒. เข้ าใจกลไกควบคุมการออกดอก
signal/ receptor/
gene expression
ทบทวนโครงสร้ างดอก
เนือ้ เยื่อเจริญ: floral meristem
โครงสร้ างของดอก
ชัน้ ของดอก (whorl) 4 ชัน้
Flowering genes
ABC model: three floral organ identity genes
Homeotic mutation
Flowering signals and receptors
Photoperiod: day length controls of flowering
Short-day plants
Long-day plants
Phytochrome control of flowering
Vernalization: cold promotes flowering
Four developmental pathway for flowering
Taiz and Zeiger (2002)
เข้ าใจกลไกควบคุมการออกดอก
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