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Thermal Environment During Endosperm Cell Division and Grain Filling in Maize: Effects on Kernel Growth and Development in Vitro¹

Relative effects of temperature during endosperm cell division (lag phase) and the effective grain-fill period (EGFP) thephysiology of kernel development and final kernel mass in maize (Zea mays L.) were studied in vitro. Kernels were cultured at 15, 30, and 35°C during most of the lag phase. Before the start of the EGFP some kernels were transferred to each of the other temperature regimes while others remained at the original temperatures. When 30°C was maintained through the lag phase and EGFP, kernel mass was 77% of that observed for kernels from field-grown ears. Temperature extremes (15 or 35°C) during either period of kernel development reduced final kernel mass, however, an unfavorable thermal environment during the lag phase caused the most reduction. Detrimental effects sustained in the lag phase prevailed when kernels were transferred to a more conducive (30°C) thermal environment during EGFP. Regardless of temperature during the EGFP, final kernel mass was 3 to 10 times higher when the lag phase temperature was 30°C. The data also showed that duration of EGFP was mediated primarily by prevailing temperature during EGFP while kernel growth rate during the EGFP was mediated in part by thermal history during the lag phase. High levels of soluble sugars were found in the endosperm during both stages of kernel development under adverse thermal environments (15 or 35°C). This suggested that low substrate level was not the cause of the reduced kernel growth rate and lower kernel weight observed at these temperatures. High temperature during the lag phase appeared to have the greatest negative effect on endosperm starch deposition during EGFP even when a favorable EGFP temperature (30°C) was provided. These data show that temperature extremes during the lag phase may mediate final kernel size by reducing endosperm sink capacity established during the lag phase or by reducing starch deposition in endosperm cells during the subsequent EGFP.

Key Words: Temperature • Endosperm starch content • Endosperm soluble sugar content • Effective grain-filling period • Lag phase • Linear fill period • Kernel endosperm sink capacity

² Associate professor, grad research assistant and professor, respectively, Dep. of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108.

Received for publication March 14, 1983.

This article has been cited by other articles:

				P. Monjardino, A. G. Smith, and R. J. Jones Zein Transcription and Endoreduplication in Maize Endosperm are Differentially Affected by Heat Stress Crop Sci., November 21, 2006; 46(6): 2581 - 2589. [Abstract] [Full Text] [PDF]