Heat Stress Effects on Forage Quality Characteristics of Maize (Zea mays) Cultivars

Heat stress adversely affects the plant quality characteristics leading to altered forage quality. Purpose of this study was to determine the comparative changes in heat tolerant (Sultan) and heat sensitive (S-2002) maize (Zea mays L.) varieties for the nutritional quality characteristics over short intervals. Heat stress was applied by shifting the plants into an illuminated growth chamber at 40oC, while control plants were kept in another chamber at 27oC. Sultan manifested greater shoot fresh and dry weight and greater shoot water contents than S-2002 under heat stress. The varieties showed no specific trend of changes in the levels of soluble nitrate (SN), soluble phosphate (SP) and K+ under control; while Sultan indicated no variation in SN, some reduction in SP and increased in K+, while S-2002 indicated increase in the levels of SN and SP, while no great difference in K+ contents under heat stress. This was attributed to heat induced reduced utilization of the available nutrients for incorporation into structural components. Although starch, oil and protein were variable in both the varieties under control condition, heat stress reduced starch contents of both the varieties, while oil and protein contents increased in Sultan but decreased in S-2002. Crude fiber increased greatly in Sultan than S-2002 under heat stress. Heat stress improved the nutritive value and metabolizable energy in Sultan but decreased in S-2002. It is concluded that tolerant maize, by virtue of better performance and nutritive value, could be a better choice for use as forage plant if cultivated in the warmer climates. © 2010 Friends Science Publishers