The biological role of abscisic acid in precocious seed germination
Download
1 / 11

The Biological Role of Abscisic Acid in Precocious Seed Germination - PowerPoint PPT Presentation


  • 96 Views
  • Uploaded on
  • Presentation posted in: General

The Biological Role of Abscisic Acid in Precocious Seed Germination. Present by Collin Mecke April 1 st 61.325. Introduction to ABA. -Synthesis of ABA occurs in the chloroplasts and other plastids using the terpenoid pathway (fig 23.2) Detected in all parts of the plant

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

The Biological Role of Abscisic Acid in Precocious Seed Germination

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The Biological Role of Abscisic Acid in Precocious Seed Germination

  • Present by Collin Mecke

  • April 1st

  • 61.325


Introduction to ABA

-Synthesis of ABA occurs in the chloroplasts and other plastids using the terpenoid pathway (fig 23.2)

  • Detected in all parts of the plant

  • Transported by both phloem and xylem

  • Inhibits stomata opening

  • Regulates seed and bud dormancy


Discovery of ABA

  • Unknown inhibitory compounds that effect the dormancy of seeds and buds were known about for a long period

  • Inhibitory compounds that differed from auxin were discovered (1953)

  • A substance that promotes abscission in cotton fruit was found ten years later and called Abscission II (1963)

  • At the same time another compound that promoted bud dormancy was found and call Dormin

  • These two substance (Abscission II and Dormin) were found to be identical and called Abscisic Acid.


How is it Measured?

Bioassay-Measuring coleoptile growth inhibition. Minimum detection is 10-7 M

-Closure of stomata (10-9M)

Physical Methods- Gas Chromatography (10-13g)

-High Performance Liquid Chromatography

Immunoassay-Recognition of ABA by antibodies

(10-13g)


How ABA Causes Dormancy

  • At high levels of ABA (just before dormancy occurs) late-embyrogenesis abundant proteins (LEA) are produced

  • LEA’s are thought to be involved in desiccation tolerance

  • ABA has been shown to affect the amount and composition of storage proteins in a double mutant of Arabidopis (aba/abi3-1) and ABA deficient mutants of maize.

  • This process is called embryo induced dormancy


Precocious Germination

-Immature embryos were removed from seeds and cultured midway through development (before the onset of dormancy)

-These embryos germinated precociously (without passing through normal dormancy)

- When ABA was added to the medium precocious germination did not occur.


Further Evidence

  • Zea maize has several mutant species; vp2, vp5 and vp7 that are ABA deficient (fig 23.2)

  • The embryos of these plants germinate precociously on the cob. This process is called viviparous.

  • The addition of exogenous ABA prevented precocious germination.

  • Also, there is a vp1 mutant which is insensitive to ABA. It will germinate precociously even with the addition of exogenous ABA.


Current Research

  • It has been well documented that the absence of ABA causes precocious germination.

  • Is a certain amount of GA required?

  • Fluridone was used to cause ABA deficiency and paclobrutrazol or ancymidol to reduce GA in corn

  • Measured the amount of GA in each seed and whether precocious germination occurred.

  • It was found that a minimum amount of GA was required for precocious germination.


Current Research

  • vp5 maize mutant was cross with a dwarf maize (d1-GA deficient)

  • The resulting double mutants (vp5/d1) did not undergo precocious germination

  • Addition of exogenous GA to double mutant did produce precocious germination


Current Research

  • Low levels of GA did not diminish vivipary in vp1 mutants.

  • This suggests that the GA and ABA signaling converges upstream from the site of vp1 action.

  • It was proposed that vp1 controls seed maturation and germination through 2 processes;

    1. Transcriptional activator of ABA-inducible gene

    expression

    2. ABA-independent repressor of germination specific

    gene expression


Uses in Bio-Tech

  • Causing seeds to germinate faster (skipping the dormancy stage of development) will results in plants growing to maturity faster.

  • This could result higher crop production.


ad
  • Login