Response of Phenology and Yield-related Characters to Elevated Air Temperature in Maize

Abstract

As in the other C4 crops, maize shows considerably better adaptation to an environment of high temperature than C3 crops. However, maize yield is expected to decrease by supra-optimal temperature that is projected to occur frequently under the accelerating global warming. The objectives of this study were to (1) assess the response of maize development, flowering, kernel set, and yield to elevated temperature and (2) the simulation performance of maize growth models under this high temperature environment. Early maturing maize hybrid cultivars Chalok#1 and Junda#6 which were bred and grown in south Korea and northern China, respectively were tested in the plastic houses (37.27˚N, 126.99˚E

Suwon, Korea) that were controlled to the target temperatures of ambient temperature (AT), AT+1.5℃, AT+3℃ and AT+5℃ at one sowing date in 2013 and three different sowing dates in 2014. For temperature treatments, a seedling of V3 – V4 stage was transplanted in 1/2000a Wagner pot and five pots were transferred to each plastic house. Air temperatures were monitored with data logger equipped with platinum resistor thermoprobe throughout the growing season. Growth durations from emergence to anthesis and from anthesis to physiological maturity tended to decrease but not necessarily with elevated temperature treatments above ambient. Above a certain levels of temperature elevation those growth durations were rather lengthened again. High temperature-dependent variations were greater in grain filling duration than in vegetative period before anthesis. These tendencies were more obvious in Junda#6 than Chalok#1. Temperature elevation did not affect the interval from anthesis to silking (ASI) in all experimental variables. Ear position, tassel branches, and final leaf number were not significantly different among temperature treatments at all sowings in both cultivars but tassel branches tended to increase with temperature elevation in Junda#6. Daily anthesis and silking patterns followed the normal distribution in both maize cultivars. 50% anthesis occurred after 2.32 to 3.63 days and 2.74 to 2.99 days from initial anthesis in Chalok#1 and Junda#6, respectively. 50% silking reached at 2.08 to 2.49 days and 1.61 to 2.85 days from initial silking in Chalok#1 and Junda#6, respectively. Elevated temperature delayed only the duration from initial to 50% anthesis in Chalok#1. Grain yield tended to decrease along with temperature elevation in both cultivars. The yield reductions due to temperature elevation were resulted from the decrease in kernel number rather than in individual kernel weight. Grain yield exhibited highly significant correlations (r>0.9) with kernel number but no or low significant correlation with kernel weight. Kernel number reduction due to temperature elevation resulted from the decrease of differentiated ovule number and the increase of kernel set failure. High temperature- induced kernel set failure resulted from un-fertilization of ovules in both cultivars and abortion of fertilized ovules in Chalok#1. Individual kernel weight was not significantly different among temperature elevation treatments but showed significant differences among sowings in both cultivars. High temperature-induced reduction in kernel set, kernel number, and grain yield was much more sensitive in Junda#6 than in Chalok#1. Percent un-fertilized ovules showed highly significant positive with average temperatures during silking period of six days only in Junda#6, while percent aborted kernels showed no significant correlations with temperatures in both cultivars. The responses of percent fertilized ovules to temperatures during silking period were welled to logistic functions in Junda#6, while the distinctive responses were not detected in Chalok#1. Critical temperatures inducing 50% un-fertilization were estimated to be 28.6, 37.3, and 24.7℃ in average, maximum, and minimum temperatures, respectively in Junda#6. Two maize growth models, CERES-Maize and IXIM-Maize, predicted the growth durations and grain yields fairly well around ambient temperature conditions while underestimated under elevated temperature conditions. The gaps became greater along with temperature elevation in both cultivars. CERE-Maize underestimated grain yield much greater than IXIM-Maize under elevated temperature conditions. These poor estimations of grain yield in elevated temperature resulted from the poor temperature response of kernel weight and kernel number in both models. In conclusion, global warming projected in the future is expected to affect maize yield adversely in Korea, and crop models need further improvement for assessing the climate change impact on maize yield in the future.