Abstract
Nocturnal dark respiration (Rn) in wild type and transgenic soybean plants grown at SoyFACE research facility, Illinois, USA under ambient and elevated CO2 conditions was examined in this study. Transgenic plants were transformed to overexpress a key Calvin cycle enzyme sedoheptulose-1,7-bisphosphatase (SBP) which is thought to improve yield in the field by at least 11%. Heating was applied using infrared heaters mounted 1.2 m above the plants in the field during the growing season of 2015 summer and Rn measurements taken for wild type and SBP overexpressors at ambient and elevated CO2 plots from V4 to R6 developmental stages. The objective was to study the effects of elevated CO2 of approximately 585 μmol mol-1 and +3.5 increase in temperature on wildtype and transgenic SBP plants. Measurements were recorded at growth and constant temperature for both varieties. Experimental plants were transferred to a controlled growth chamber at V4 and R6 developmental stages and the temperature responses examined from 15 to 40°C. Specific leaf area (SLA) and its relations to Rn were also determined. Results indicate that SLA decreased significantly relative to control in the wild type and transgenic soybean plants by R6. Differential responses of Rn to ambient and elevated CO2 treatments were observed in both plants. In addition, results indicate that Rn declined generally in both varieties under elevated temperature. Lower Rn was attributed to temperature acclimation. Key words: Dark respiration, soybean, ambient CO2, elevated CO2, transgenic plant, sedoheptulose-1,7-bisphosphatase (SBP), heating, acclimation.
Highlights
INTRODUCTIONWith changing environmental conditions due to global warming, plants experience variations in photosynthesis
With changing environmental conditions due to global warming, plants experience variations in photosynthesis.These variations can be short-term or long-term and affect metabolic processes
Responses were examined in some experiments in combination with continuous heating, in order to provide a clearer view of the physiological impacts of elevated temperature, which is projected to occur with global change
Summary
With changing environmental conditions due to global warming, plants experience variations in photosynthesis. There is evidence that, overexpression of the enzyme increases the yield of tobacco and soybean in the field (Hay, 2012; Rosenthal et al, 2011) Respiration in these transgenic species has not been explored in relation to changes in growth CO2. The current research presented here focused on dark respiration in relation to SLA, elevated CO2 and temperature in a wild type soybean plant and transgenic species which have been modified to express SBP. The objective was approximately to study the effects of 585 μmol mol-1 and elevated CO2 +3.5 increase of in temperature on wild type and transgenic SBP plants These plants were grown in the field at ambient and elevated CO2 and respiration measured at night (nocturnal respiration). Responses were examined in some experiments in combination with continuous heating, in order to provide a clearer view of the physiological impacts of elevated temperature, which is projected to occur with global change
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