Use of postharvest calcium application in extending the keeping quality of tomatoes and the elucidation of calcium involvement in ethylene biosynthesis
Njoroge, Charles Kimani
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/19114
Description
Title
Use of postharvest calcium application in extending the keeping quality of tomatoes and the elucidation of calcium involvement in ethylene biosynthesis
Author(s)
Njoroge, Charles Kimani
Issue Date
1992
Doctoral Committee Chair(s)
Kerbel, Eduardo L.
Department of Study
Food Science and Human Nutrition
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Agriculture, Food Science and Technology
Biology, Plant Physiology
Language
eng
Abstract
Calcium at 0.75%w/v CaCl$\sb{2}$ and 1.5%w/v CaCl$\sb2$, inhibited ripening of both fresh market (caruso) and processing (UC82) tomatoes and resulted in an extended storage period of 2-3 days. The delay in ripening was probably due to the inhibitory effect of calcium on ethylene biosynthesis which was observed in both caruso and UC82 tomatoes.
The above calcium levels inhibited ethylene production in mature green, pink and red tomatoes. Calcium treatment resulted in accumulation of ACC and reduced EFE activity but had no effect on ACC synthase activity or levels of MACC which implied that calcium inhibited ethylene production by inhibiting EFE.
The inhibitory effect of EFE by calcium and the accumulation of ACC were relieved by W-7 while W-5 had no effect. W-7 did not affect ACC synthase activity or MACC concentration. W-7 and W-5 are both calmodulin antagonist with almost an identical chemical structure except that W-7 is a larger molecule which makes it more hydrophobic and therefore binds calmodulin better than W-5. The inhibition of ethylene biosynthesis by calcium is reversed by W-7 and TFP. These results taken together suggest that the inhibition of ethylene by Ca$\sp{2+}$ is mediated through calmodulin. Calmodulin regulates EFE activity either by direct interaction of the enzyme with Ca$\sp{2+}$- calmodulin complex or indirectly through phosphorylation of the enzyme by protein kinase(s). The protein kinase(s) could be either Ca$\sp{2+}$- dependent only or Ca$\sp{2+}$- calmodulin dependent. As suggested by our results the two regulatory mechanisms could be operating simultaneously.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
