Heat Stress during Late Vegetative Growth of Maize: Effects on Phenology and Assessment of Optimum Temperature.

CICCHINO, M.; RATTALINO EDREIRA, J.I.; OTEGUI, M.E.

CROP SCIENCE

CROP SCIENCE SOC AMER

Lugar: Baltimore; Año: 2010 vol. 50 p. 1431 - 1437

0011-183X

Prediction of phenology is based on thermal time (TT) computation, which requires the correct defi - nition of base (TB) and optimum (TO) temperatures. Most information on these traits came from controlled environments using a wide range of mean air temperatures (TX), including TX > TO and TX < TB. These conditions are rarely found in fi eld environments. We assessed the effect on development of day-time temperatures above TO during late-vegetative growth of maize (Zea mays L), and established a model based on TT computation on a per hour (TTh, in °C h) rather than per day basis (TTd) for TO estimation. Field experiments included two temperature regimes (TC: control; TH: heated) between V11 and tasseling of TC. We registered temperature at ear level, and dates of anthesis and silking. We computed developmental rates (DR), TTh above 8°C during treatment period (TTh1) and between V11 and silking (TTh2), a stress index based on the quotient of differences in TTh (ΔTTh) between TH and TC (SI = ΔTTh2/ΔTTh1), and TO. Heat stress caused a delay in fl owering events, and a decline in DRs. Estimated TB was higher (12.7°C) than normally used in computations. Estimated TO was within the expected range (36°C > TO > 30°C), independently of TB. Stressful temperatures promoted a delayed in silking, identifi ed as an increase of at least 2.14°C h in TTh for each degree above TO. Estimated TO differed between growing seasons (P = 0.04), suggesting possible variation due to climatic effects.