|SIEBERS, MATTHEW - University Of Illinois|
|YENDREK, CRAIG - Former ARS Employee|
|LOCKE, ANNA - University Of Illinois|
|DRAG, DAVID - University Of Illinois|
|Ainsworth, Elizabeth - Lisa|
Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2016
Publication Date: 3/1/2017
Citation: Siebers, M.H., Slattery, R.A., Yendrek, C.R., Locke, A.M., Drag, D., Ainsworth, E.A., Bernacchi, C.J., Ort, D.R. 2017. Simulated heat waves during maize reproductive stages alter reproductive growth but have no lasting effect when applied during vegetative stages. Agriculture, Ecosystems and Environment. 240:162-170.
Interpretive Summary: To meet future global food demand without large changes in land use, it is projected that per hectare crop productivity must double by 2050. The rate of yield increase for some major crops like rice and wheat, however, has slowed since the 1960’s, and current yield trends will not meet the projected goal. Furthermore, improvements to the rate of yield increase must be accomplished in a more variable climate. The IPCC’s fifth assessment report forecasts increasing mean global temperatures with an increase in the frequency, intensity, and duration of heat waves. Several recent studies suggest that in the most productive regions in the United States, maize is grown near or even above its temperature optimum. The objective of this experiment was to determine the immediate impacts of heat waves on maize physiological properties and their subsequent effects in determining yield response. Intense, short duration heat waves were applied to field-grown maize during vegetative or reproductive stages using infrared (IR) heating technology. The primary effects of heat waves on phenology, leaf gas exchange, and plant and soil water status were quantified and compared in relation to heat wave timing. Although temperature 120 stress during vegetative stages can affect maize A and growth, we hypothesized that short, intense heat treatments during the more sensitive reproductive stage would have greater negative impacts, resulting in more pronounced reductions in yield parameters.
Technical Abstract: Due to climate change, heat waves are predicted to become more frequent and severe. While long-term studies on temperature stress have been conducted on important crops such as maize (Zea mays), the immediate and or long-term effects of short duration but extreme high temperature events during key developmental periods on physiological and yield parameters are unknown. Therefore, heat waves were applied to field-grown maize in east central Illinois using infrared heating technology. The heat waves warmed the canopy approximately 6 to 8 C above ambient canopy temperatures for three consecutive days during vegetative development (Wv1) and during an early reproductive stage (silking; Wv2). Neither treatment affected aboveground vegetative biomass, and Wv1 did not significantly reduce reproductive biomass. However, Wv2 significantly reduced total reproductive biomass by 16% (p<0.1) due to significant reductions in cob length (p<0.1), cob mass (p<0.05), and husk mass (p<0.05). Although not statistically significant, seed yield was also reduced by 13% (p=0.15) and kernel number by 10% (p=0.16) in the Wv2 treatment. Soil water status was unaffected in both treatments, and leaf water potential and midday photosynthesis were only transiently reduced by heating with complete recovery after the treatment period. Therefore, the reduction in Wv2 reproductive biomass was most likely due to greater sensitivity of reproductive structures to direct effects of high temperature stress.