Heat tolerance of maize with reference to some physiological characteristics

Abstract

Various physiological characteristics along with growth of a tropical maize genotype, F-212, were analyzed at 42/30 °C and 25/22 °C at seedling stage in highly controlled conditions. Plant growth was decreased seriously though was not checked completely at 42/30 °C. Photosynthesis was decreased seriously while dark respiration and intercellular C02 concentration were increased considerably by high temperature. Stomatal conductance as well as transpiration were noticeably higher in the plants grown at 42/30 °C than the plants at 25/22 °C. High concentration of glucose was measured from the plants grown at high temperature though a dramatic reduction of starch concentration was detected from the same plants. Concentration of ABA in leaf no. 2 was increased about 4 times at 42/30 °C than at 25/22 °C. Chlorophyll a fluorescence as represented by quantum yield of electron transport at PS II (<#>PS II) and efficiency of electron transfer at PS II (Fv/Fm) was lowered due to high temperature. The measured physiological characteristics, however, indicated that the reduction of photosynthesis at high temperature was not due to stomatal response to high temperature rather due to non-stomatal limitations.