Interested Members of the University Community are invited to attend the Final Oral Examination for the Degree of Master of Science of William Kramer of the Department of Plant Agriculture 

Date: Thursday, December 16
Time:  1:00 pm 
Location: In Room CRSC 202, Crop Science Building for those who are students/faculty of the University of Guelph, or on Zoom for those who are unable to attend in person.

Zoom link: https://zoom.us/j/92413143704?pwd=VksvL3ZpblpTcGRrWE1Vc1pUQlVOUT09 
Meeting ID: 924 1314 3704
Passcode: 267566. 

Thesis Title: “Impact of Low R/FR Light Environments on Nitrogen Assimilation in Corn (Zea mays)“ 

Advisory Committee
Dr. Clarence Swanton (Advisor)
Dr. François Tardif (Co-Advisor)
Dr. Andrew McKenzie-Gopsil

Examination Committee
Dr. Peter Pauls (Chair)
Dr. François Tardif
Dr. Clarence Swanton
Dr. Gale Bozzo                                       

ABSTRACT 

In the absence of direct resource competition, far-red light reflected from neighbouring weeds compromises light quality (red to far-red ratio; R/FR) which inactivates phytochrome resulting in the regulation of various physiological processes. The main objective of this research was to investigate the effects of low R/FR light on nitrogen assimilation in corn. To explore this, changes to the nitrogen assimilation pathway were measured in corn seedlings 9-days after emergence under low R/FR and control light conditions. The observed results indicated that nitrate levels increased in corn leaf and root tissue. Additionally, nitrate accumulation was not accompanied by changes in ammonium levels and actives of nitrate-reductase, nitrite reductase, and glutamine synthetase; However, ferredoxin-dependent glutamine oxoglutarate aminotransferase (Fd-GOGAT) activity decreased under low R/FR light conditions. Changes in the N assimilation pathway appear to be phytochrome B-independent, as Arabidopsis phyB mutant expressed no change in nitrate levels compared to wild-type Arabidopsis. Accumulation of NO₃^- as an early response to resource-independent weed competition has yet to be identified in the literature. These results offer novel insights into understanding the physiological mechanism involved in weed-crop competition for nitrogen and highlight the importance of mitigating early-season weed competition.