Purpling in Maize Hybrids as Influenced by Temperature and Soil Phosphorus
1987
Purpling in maize (Zea mays L.), which has been prevalent in Ontario in recent years, has been attributed to combinations of P deficiency, low temperature, and genotype. The intensity of purpling in maize hybrid seedlings grown in growth rooms in an Aqnic Hapludalf soil at three P levels (4,22,100 mg L⁻¹ NaHCO₃-extractable P) and two air temperatures (15/10 and 25/20°C, light/dark) was studied to determine the extent to which differential purpling at low temperature could be attributed to variable shoot P concentration. All hybrids tested (Pioneer 3720, 3732, 3780A, 3949, PAG SX111, Pride 1169) showed some purpling at very low soil P and 15/10°C temperatures. At 25/20°C and very low soil P, Pioneer 3732 and Pride 1169 were severely purpled, Pioneer 3780A and PAG SX111 were intermediate, and Pioneer 3720 and 3949 had the least purpling. Although intensity of purpling decreased with increasing P concentration in shoots, at 15/10°C some hybrids showed purpling even with 5 g P kg⁻¹ DM in shoot. Hybrids differed markedly in intensity of purpling at similar P concentration. Anthocyanin content decreased with increasing shoot P concentration, but there were marked differences among hybrids in anthocyanin content at a given shoot P concentration. There were also marked differences in degree of purpling among hybrids with similar anthocyanin contents. The effects of genotype and temperature on degree of purpling may be due to: (i) reduced shoot P concentration; (ii) higher anthocyanin content regardless of shoot P concentration; or (iii) greater purpling at similar anthocyanin contents. The appearance of purple color in maize seedlings is not necessarily due to inadequate P concentration in the plant.
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