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High Temperatures during Endosperm Cell Division in Maize

A Genotypic Comparison under In Vitro and Field Conditions

^a ExSeed Genetics L.L.C., 2901 South Loop Dr. Bldg #3, Suite 3360, ISU Research Park, Ames, IA 50010
^b Department of Agronomy and Plant Genetics, 411 Borlaug Hall, 1991 Upper Buford Circle, Univ. of Minnesota, St. Paul, MN 55108

View larger version (91K): [in a new window]   Fig. 1. Exposure of field-grown maize kernels to high temperatures (35°C) using an electric heating mat fitted closely around the ear. A micro-thermocouple was placed between husk leaves and kernels, and was connected to a feedback-loop regulated electronic temperature controller. Ten of these devices were rack-mounted and used simultaneously to regulate the temperature of 10 individual ears. For uniform heat distribution, ears were wrapped with aluminum foil with both ends kept open for air circulation. This setup was replicated for control ears, except that they were not heated.

View larger version (25K): [in a new window]   Fig. 2. High temperature-induced (35°C) changes in the growth of B73 (panel A) and Mo17 (panel B). Pictures were taken at 34 d after pollination (DAP) for in vitro-grown kernels. For field-grown kernels, pictures were taken at 28 DAP for B73, and at 24 DAP for Mo17. The numbers in the boxes show percentage abortion of kernels in each treatment.

View larger version (26K): [in a new window]   Fig. 3. High temperature-induced (35°C) changes in the dry weight accumulation patterns of B73 (A, B) and Mo17 (C, D) kernels grown either in vitro (A, C) or under field conditions (B, D). Data are means ± SE of three replications. Data points followed by the same letter do not differ significantly at the P 0.01 level.

View larger version (183K): [in a new window]   Fig. 4. The scanning electron micrographs (SEMs) of longitudinal sections of maize kernels at 11 d after pollination (DAP) of field-grown B73 (A, B, C) and Mo17 (D, E, F). Controls (A, D) and kernels exposed to high temperature (35°C) at 5 DAP for 4 (B, E) and 6 d (C, F). Pe = pedicel; EN = endosperm; P = pericarp; E = embryo; and N = nucellus. Scale bar = 100 µm.

View larger version (44K): [in a new window]   Fig. 5. Comparison of the effect of high temperature (35°C) on the endosperm cell number of B73 (A, C) and Mo17 (B, D) grown either in vitro (A, B) or under field conditions (C, D), and exposed to high temperatures for 4 and 6 d, beginning at 5 d after pollination (DAP). Data are means ± SE of three replications. Data points followed by the same letter do not differ significantly at the P 0.01 level.

View larger version (41K): [in a new window]   Fig. 6. Comparison of the effect of high temperature (35°C) on the starch granule number of B73 (A, C) and Mo17 (B, D), grown either in vitro (A, B) or under field conditions (C, D), and exposed to high temperatures for 4 and 6 d, beginning at 5 d after pollination (DAP). Data are means ± SE of three replications. Data points followed by the same letter do not differ significantly at the P 0.01 level.