Modeling Preemergent Maize Shoot Growth: II. High Temperature Stress Conditions
1996
Weaich, Karl | Bristow, Keith L. | Cass, Alfred
Highs oil temperatureas re a significant constraint to crop establishment. Exposure of preemergent maize (Zea mays L.) to temperatures in excess of 40°C stops shoot elongation and maya lso damaget he seedling, reducing subsequent shoot growth in the physiological temperature range (9 to 40°C). At present, there is little quantitative understanding of the effects of high temperature stress on preemergent maize shoot growth. Consequently, existing maize emergence or preemergent maize shoot growth models are restricted to the physiological temperature range. The work described in this paper quantified the effect of supramaximum temperatures (temperatures greater than 40°C) on maize shoot growth, and in particular on its component parts, the coleoptile and first internode. The major impact of supramaximum temperatures on shoot growth was due to a severe reduction in the first internode growth rate, which was correlated with the maximumtem peraturer eached during the day. We also found that, under diurnally varying temperature conditions, coleoptile growth ceased only at 45°C, rather than at 40°C as found previously in constant temperature experiments. Inhibition of shoot growth due to high temperature damage was alleviated when seedlings were grown in the physiological temperature range for 33 h. Based on these findings, a model was developed that can predict shoot growth of seedlings exposed to supramaximum temperatures. The model successfully predicted shoot growth of seedlings exposed to supramaximum temperatures as a part of the diurnal cycle. The model was unable, however, to predict seedling recovery from high temperature damage. Work done while the senior author was with the CSIRO, Div. of Soils, Davies Lab., Townsville, QLD 4814.
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