Corn Journal
  • Corn Journal
  • Author
  • Stalk Rot Booklet
  • Seed Testing
  • Corn Genetics
  • Pathology
  • Sponsors
  • Contact
"You can see a lot by just looking"-Yogi Berra

Abscission layers in corn

10/30/2018

 
Nearly all plant species shed plant parts with the function of allowing continuation of the species.  Temperate zone deciduous tree leaves reduce the supply of nutrients to the chloroplasts as summer ends.  Nitrogen and other nutrients are transported from the chloroplasts and other leaf cell contents to plant parts that will survive the winter.  This physiological change reduces movement of auxin hormones to the cells at the base of the leaf where it is connected to the stem.  This stimulates the production of lignin and suberin in cells immediately below a layer of cells called the abscission layer. This thickening of cell walls essentially cuts off all translocation of water and nutrients from the stem to the leaves.  It also causes the leaves to break from the stem at the point of the abscission layer while preserving the moisture in the stem. 
 
The same process occurs in all plants, including in the tropics, although not as remarkably simultaneously colorful as with trees in the temperate zone at this season in north America.  Similar physiological phenomena occur as fruit are released from the base plant.  This was also true for the Teosinte species selected 10,000 years ago by someone because, contrary to most Teosinte plants, this genotype formed abscission layer at the base of the fruit (kernel) but did not quickly allow the kernel away from the parent plant.  Maintaining the attachment of the kernel to the rachis (cob) even after abscission layer (black layer) formed allowed more efficient harvest for those folks 10,000 years ago, as it does for the modern farmer.  Selection of this character by corn breeders since that time have attempted to maintain appropriate attachment of the kernel (fruit) to the cob thru harvest.  
 
Leaves surrounding the corn ear, the husks, undergo similar abscission layers after the black layer is formed in the kernels.  This cuts off the water movement into the husk leaves, usually causing them to withdraw from being tightly wrapped around the ear.  This is associated with faster evaporation of water from the kernels.  Likewise, abscission occurs in cells at the base of the cob. This further removes water movement into the cob, allowing for further drying of cob and kernels.  Corn breeders challenge is to select genetics that allow rapid kernel drying while maintaining attachment of the ear to the corn plant until harvest.  Stress conditions may cause premature formation of abscission layers in kernels and husk leaves.  This has been associated with ears dislodging from the plant.  Pests such as European Corn Borer have been associated with premature dropping of ears in the field. 
 
The balance of timely formation of abscission layers to allow drying of grain, maintaining adequate attachment of kernels to cob and ears to the plant when grown in multiple environments continues to be a complex genetic feat.  Combining these characters with maximum translocation of sugar to the grain before formation of the abscission layer at the base of the kernel adds to the corn breeders’ accomplishments for the past 10,000 years.

Comments are closed.

    About Corn Journal

    The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.

    Archives

    December 2021
    November 2021
    October 2021
    September 2021
    August 2021
    July 2021
    June 2021
    May 2021
    April 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015

    Categories

    All

    RSS Feed

© COPYRIGHT 2023. ALL RIGHTS RESERVED
  • Corn Journal
  • Author
  • Stalk Rot Booklet
  • Seed Testing
  • Corn Genetics
  • Pathology
  • Sponsors
  • Contact