Presentation is loading. Please wait.

Presentation is loading. Please wait.

Flowering - Floral Induction. Flowering - Floral Induction (branch bud ----> flower bud) violets, roses, chrysanthemums Chailakhan 1920s Russian Florigen.

Similar presentations


Presentation on theme: "Flowering - Floral Induction. Flowering - Floral Induction (branch bud ----> flower bud) violets, roses, chrysanthemums Chailakhan 1920s Russian Florigen."— Presentation transcript:

1 Flowering - Floral Induction

2 Flowering - Floral Induction (branch bud ----> flower bud) violets, roses, chrysanthemums Chailakhan 1920s Russian Florigen Amount of light and photoperiods already known to be important.

3 Photoperiodism the ability of the plant to respond to different lengths of light treatment W. W. Garner & H. A. Allard - U. S. Ag. Dept. 1918… Maryland Mammoth –large-leaved mutant –lack of flowering –greenhouse plants …various stages most flowered in early December! DAYLENGTH critical factor Short Day, Long Day, Day Neutral plants

4 Short Day Plants Flower only when day length is shorter than some critical value. –Pointsetta, cocklebur, soybean.. - qualitative will not flower without a critical photoperiod –wheat, rye,.. - quantitative will flower without a critical photoperiod but will take longer

5 Short Day Plants Flower only when day length is shorter than some critical value. –soybean.. - qualitative

6 Long and Short Day Plants May Flower at the Same Time Henbane (11 hrs.), Cocklebur (15 hrs.)

7 Long and Short Day Plants May Flower at the Same time

8 PHOTOPERIODISM Some plants need several days at the proper daylength. Winter & Summer Solstices

9 PHOTOPERIODISM K. Hamner (U of Cal.) and J. Bonner (CIT) 1938 Sensitive light receiving system (pigment) at work. Cocklebur: –15 hrs of light/9 hrs dark = flowers –15.5 hrs of light/8.5 hrs dark = no flowers –15 hrs of light/9 hrs dark with interrupted dark = no flowering (Dark period is more critical than light period for Floral Induction - initiation of floral primordia.)

10 PHOTOPERIODISM K. Hamner (U of Cal.) and J. Bonner (CIT) 1938

11 PHOTOPERIODISM REDEFINED K. Hamner (U of Cal.) and J. Bonner (CIT) 1938: –Short Day Plants uninterrupted darkness must be of a certain duration. (so much darkness or more) –Long Day Plants uninterrupted darkness must be less than a certain maximum value. (so much darkness or less) –Day Neutral Plants Flowers at a certain level of maturity or in response to some environmental factor other than the photoperiod.

12 PHOTOPERIODISM K. Hamner (U of Cal.) and J. Bonner (CIT) 1938

13 PHOTOPERIODISM

14 H. A. Borthwick and S. B. Hendricks 1950s US Ag

15 Photomorphogenic Responses

16

17 H. A. Borthwick and S. B. Hendricks 1950s US Ag –Action spectra studies - flowering and others –Subjected plants to various wavelengths during dark period ----> responses All photomorphogenic responses studied had similar responses … Predicted: the photochrome pigment –2 forms - 1.) PR - red light absorbing form – 2.) PFr - Far-red light absorbing form (Active Form)

18 Photomorphogenic Responses Phytochrome is ubiquitous in plants - found in all tissues. Has been isolated and purified. Phycocyanin like

19 Photomorphogenic Responses Phytochrome Action Spectra:

20 Photomorphogenic Responses Mechanism of Phytochrome Action: PR > PFr Red Light PR < PFr Far-red Light Half Life of PFr = 2.5 hours (based on conformational changes in phytochrome)

21 Photomorphogenic Responses (3) Chromoproteins (chromatophore & apoprotein): –Phytochromes (5) PR & PFr –Cryptochromes Blue & UV –Photochromes Blue & UV

22 Photomorphogenic Responses Control of Gene Activation: Actinomycin inhibits transcription & stops light responses

23 Photomorphogenic Responses

24 Less etiolation with higher amount of PFr Chenopodium albalambs quarter

25 Bud Dormancy Wareing (1950s) Fagus beech tree –initiated by short days –relieved by long days –reception site: leaf bud scales

26 Bud Dormancy Initiation factors: photoperiod, lack of water, cold treatment (vernalization). –ABA - increases during bud dormancy –GA - decreases during bud dormancy –reception site: leaf bud scales –GA:ABA ratio a factor

27 Seed Dormancy Hard Seed Coat –prevents imbibition of water, gas exchange and growth –helps maintain the seed bank –Scarification any treatment that breaks the seed coat –MECHANICAL (INSECTS) –ACID –FIRE

28 Seed Dormancy Stratification –cold treatment of seeds Ambient Factors: –1.) temperature (near freezing, -2--> 7 degrees C) –2.) time (7 --> 12 weeks …)

29 Dormancy Lange 1950s Hyoscyamous niger henbane –annual and biennial types –varied time and temperature of treatment for biennial –shorter vernalization, longer to flowering

30 Vernalization/Stratification Petkus Rye - long day plant 15 1/2 wks to flower –spring annual –winter annual also needs vernalization (and/or stratification) flowers in 7 1/2 wks with cold treatment

31 Vernalization/Stratification Petkus Rye - –winter annual

32 Deveralization/Destratification High temperatures (35 degrees C) are effective in devernalization/destratification if cold treatment is short.


Download ppt "Flowering - Floral Induction. Flowering - Floral Induction (branch bud ----> flower bud) violets, roses, chrysanthemums Chailakhan 1920s Russian Florigen."

Similar presentations


Ads by Google