Author Date

2021-08-09

Degree Name

Department

Chemistry and Biochemistry

College

Physical and Mathematical Sciences

Defense Date

2021-07-30

Publication Date

2021-08-09

First Faculty Advisor

Ryan Stewart

First Faculty Reader

Matt Arrington

Honors Coordinator

Walter Paxton

Keywords

Agave, Photosynthesis, Circadian Rhythm, Photoperiod, Drought-tolerant

Abstract

Agave uses photoperiod, among other environmental conditions, to time its circadian rhythm of photosynthesis. Two species of Agave (A. americana and A. murpheyi) were tested under two extreme photoperiod conditions (constant light and constant dark) against a normal photoperiod control (12 hours light, 12 hours dark) to identify the impact of abnormal photoperiod on circadian rhythms of Agave photosynthesis. Under constant light conditions, normal oscillations in CO2 gas exchange became unpredictable in duration and amplitude in both species and became very infrequent in A. murpheyi. Under constant dark conditions, net CO2 uptake stabilized at a negative value and oscillations ceased in both species. Under a normal photoperiod, net CO2 uptake mostly occurred during the second half of the day (phase IV) rather than at night. High nighttime temperatures (22 ℃) prevented nighttime CO2 uptake. This is likely an adaptation to prevent evapotranspiration through open stomates.