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ABSTRACT Early planting of corn ( Zea mays L.) is a strategy to avoid excessive heat and drought that often negatively influence grain production during its reproductive phase. An experiment was conducted by imposing very low (day/night, 21/13°C), low (25/17°C), and optimum (29/21°C) temperatures during seed germination and seedling growth stages under optimum moisture and nutrient conditions. Above‐ and belowground growth parameters were assessed at 18 d after seeding. Several root morphological traits were assessed using the WinRHIZO root image analysis system. Corn hybrids varied significantly for many traits measured, particularly plant component weights and root morphological parameters. Principal component analysis (PCA) and total low‐temperature response index (TLTRI) methods were used to categorize corn hybrid tolerance to low temperature and to group corn hybrids as cold tolerant, moderately cold tolerant, moderately cold sensitive, and cold sensitive. Total leaf and root weights and cumulative root length and length per unit volume were the most important morphological traits in describing hybrid tolerance to cold temperature. Based on the TLTRI method, relative scores were provided for each hybrid, which ranged from 22.45 to 29.52 among the hybrids. The hybrids CR8410VT3P, D57VP51, and R22BHR43 were classified as cold sensitive and AR1262, DKC6697, DKC6804, and M2V707 as cold tolerant based on PCA and TLTRI techniques. Based on the relative scores assigned in this study, corn producers could select hybrids to maximize corn production in an early planting production system.
Wijewardana et al. (Thu,) studied this question.