Abstract: A glasshouse study was conducted to evaluate the effects of high temperature growth conditions on the integrity of the photosynthetic pigment complex in maize (Zea mays L.) plants and to elucidate the influence of ascorbate and kinetin applications. Total chlorophyll content declined with age in all categories of plants. Ascorbate and kinetin applications tended to slow down the rate of chlorophyll loss even though these treatments did not increase the pigment content of treated plants significantly over those in untreated plants. Chlorophyll a:b ratio varied significantly with plant age under both ambient and high temperature conditions for both of ascorbate and kinetin treatments. These ratios were higher in heat stressed plants than in non-stressed plants. Chlorophyll: Carotenoid ratios varied significantly with plant age both under ambient and high temperature growth conditions for both ascorbate and kinetin treatments. These ratios were generally higher under ambient conditions than under heat stress conditions. Correlations between air temperature and pigment contents/ratios were mainly negative and were generally higher under high temperature than under ambient growth conditions. Similarity in the pattern of variation of both Chlorophyll a:b ratios and Chlorophyll: Carotenoid ratios observed in this study emphasized the close functional relationship between the pigments. Applied substances did not significantly influence the integrity of the photosynthetic light-harvesting complex at the concentrations used in this study.