Edinburgh Research Archive logo

Edinburgh Research Archive

University of Edinburgh homecrest
View Item 
  •   ERA Home
  • Biological Sciences, School of
  • Biological Sciences thesis and dissertation collection
  • View Item
  •   ERA Home
  • Biological Sciences, School of
  • Biological Sciences thesis and dissertation collection
  • View Item
  • Login
JavaScript is disabled for your browser. Some features of this site may not work without it.

Pre-harvest sprouting in wheat

View/Open
GoldCM_1991redux.pdf (25.81Mb)
Date
1992
Author
Gold, Catherine Mary
Metadata
Show full item record
Abstract
 
 
This work examines some of the factors that influence PHS in wheat, with particular emphasis on the prem ature production of alpha-amylase (PMAA) in the absence of visible sprouting.
 
Field trials in 1989 and 1990 studied alpha-amylase activity in relation to grain development in four winter wheat cultivars. W eather conditions were generally warmer and drier than average in both years. Differences in drying rate were induced by covering and wetting treatments. Fenman had a slower rate of grain drying (40%-23% moisture) than other varieties, but, within varieties, drying rate appeared not to be related to alpha-amylase levels. This lack of relationship was possibly due to the fact that all of the drying rates were relatively fast, and, apart from Fenman, levels of alpha-amylase were low. The level of dormancy and the lack of visible sprouting indicated that the alphaamylase activity observed in Fenman was due to PMAA. The increase in alphaamylase began when moisture percentage was between 40 and 35 %. Activity rose steeply, and remained high until harvest. There were differences in alphaamylase activity between the wetting and covering treatments and the control in 1989, but these were not related to effects on grain drying. There was an increase in the number of grains with high alpha-amylase activity in the covered and wetted treatm ent and it was suggested that changes in microclimate at an earlier stage of grain development may have affected sensitivity to GA, leading to subsequent development of PMAA. This was investigated in 1990. The onset of sensitivity to GA3 coincided with the increase in alpha-amylase activity in Fenman, but GA3 sensitivity was also apparent in other cultivars that did not exhibit PMAA. Fenman showed an earlier onset of GA-sensitivity than the other varieties, but neither covering nor wetting had a significant effect on GA-sensitivity or PMAA.
 
The possible role of GA in the regulation of PMAA was investigated in a trial comparing near-isogenic lines of Maris Fluntsman, differing in GA-sensitivity. Levels of alpha-amylase were reduced in dwarf {Rhtl +2 and Rht3) and semi-dwarf (Rhtl and Rht2) lines relative to the tall (rht) genotype. However, this did not appear to be related to variation in GA-sensitivity shown by developing grains. R htl showed a greater response to GA3 than the other lines. It was suggested that the genotypes may differ in sensitivity to environmental effects.
 
An attempt to identify critical stages of grain development, with respect to environmental effects on PMAA, was unsuccessful, but did indicate that constant warm and dry environmental conditions reduce alpha-amylase activity in Fenman.
 
Ear culture was used to examine the effect of drying rate on PMAA in Maris Huntsman. There was no apparent relationship, possibly due to relatively fast drying rates, but it is suggested that ear culture is a suitable system in which to study environmental effects.
 
There is considerable variation in PMAA both within and between ears, and possible reasons for this were considered. Non-destructive methods of single grain moisture determination were used to examine the relationship between alpha-amylase activity and grain moisture content. Response to GA3 appeared to vary between grains in the same ear, but there were too few data to relate this to incidence of PMAA. There appeared to be an asymmetric distribution of alpha-amylase within grains.
 
It is suggested that environmental factors may cause an earlier onset of GA-sensitivity, and that this may coincide with a moisture content sufficient to allow alpha-amylase synthesis to begin.
 
URI
http://hdl.handle.net/1842/28116
Collections
  • Biological Sciences thesis and dissertation collection

Library & University Collections HomeUniversity of Edinburgh Information Services Home
Privacy & Cookies | Takedown Policy | Accessibility | Contact
Privacy & Cookies
Takedown Policy
Accessibility
Contact
feed RSS Feeds

RSS Feed not available for this page

 

 

All of ERACommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsPublication TypeSponsorSupervisorsThis CollectionBy Issue DateAuthorsTitlesSubjectsPublication TypeSponsorSupervisors
LoginRegister

Library & University Collections HomeUniversity of Edinburgh Information Services Home
Privacy & Cookies | Takedown Policy | Accessibility | Contact
Privacy & Cookies
Takedown Policy
Accessibility
Contact
feed RSS Feeds

RSS Feed not available for this page