Genotypic and Environmental Effects on Soybean Canopy Photosynthesis
Pettigrew, William Thomas
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https://hdl.handle.net/2142/71659
Description
Title
Genotypic and Environmental Effects on Soybean Canopy Photosynthesis
Author(s)
Pettigrew, William Thomas
Issue Date
1988
Doctoral Committee Chair(s)
Hesketh, John D.
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Abstract
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.
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