BASE TEMPERATURE AND LEAF EXTENSION RATE OF MAIZE

Abstract

The present work was conducted to study variation in leaf extension rate (LER) and base temperature (T_b) in seedlings of nine corn (Zea mays L.) varieties from different ecological regions of México, exposed to thermal variations under artificial light conditions. Two experiments were conducted; experiment I (E-I) and experiment II (E-II), were carried out at Montecillo, Edo. de México. Seeds of all varieties were sown in 1 L polystyrene pots. Seedlings were maintained outdoors under artificial light at night and in dark conditions during the day. LER was determined measuring the length of leaf 1 at 18:00 and 6:00 h daily from seedling emergence up to the appearance of ligule on the second main stem leaf. T_b was determined using a linear regression model between LER and mean daily outdoors air temperature, and extrapolating the regression line to a value of zero growth. Results showed that varieties Chiautla I, Huehuetlán I and CP-560, and composites Mixteca Alta A-I and Mixteca A-P had a higher LER than variety CP-562 in experiment E-I, and composites S and Mixteca A-P had a higher LER than composites Pinto Salvatori and Zapalote Precoz, and variety CP-560 in experiment E-II. No significant differences among varieties for Tb were found in both experiments with an average value of 7.5 °C.