Genotypic and Environmental Effects on Soybean Canopy Photosynthesis

Three studies were conducted to identify environmental and genetic factors controlling soybean (Glycine max (L.) Merr.) canopy photosynthetic CO$\sb2$-exchange rates (CER) using automatic mobile transparent chambers. In the first study, CER from chlorophyll-deficient, near-isogenic lines were compared with the normal pigmented wild-type. Periods were identified when the chlorophyll-deficient lines had higher instantaneous and daily total CER. The evidence taken in this study suggests that increased light penetration into the chlorophyll-deficient canopies was the cause of the observed phenomenon. In the second study, the afternoon decline in CER in crop canopies at similar light levels as compared to the morning was investigated using grain sorghum (Sorghum bicolor (L.) Moench), cotton (Gossypium hirsutum L.), and soybean to determine if it was related to an increase in the ambient air vapor pressure deficit (VPD) causing stomatal closure. Grain sorghum was found to be more sensitive photosynthetically to the VPD increase than cotton or soybean. The results indicate that an increase in VPD was a major factor contributing to the afternoon in CER and that there appeared to be differences between species and within a species for this response. In the final study, a model was developed to predict soybean CER from leaf CO$\sb2$-exchange measurements and minimal other data acquisition. This model with an expected degree of error, particularly at low light levels, reasonably predicted soybean CER for five different genotypes during two different years.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Agronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Pettigrew, William Thomas

Contributors dc:contributor

• Hesketh, John D.

• Agriculture, Agronomy

Identifier

(UMI)AAI8908804

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71659