Effects of elevated temperature on seed germination and seedling growth on three cereal crops in Nigeria

The effect of elevated temperature on seed germination and seedling growth was investigated on three Nigerian cereal crops: maize, rice and sorghum. Seeds where then allowed to germinate in controlled growth at 37 (control: room temperature), 40, 42, 45 and 50 degree C and monitored for germination, shoot length and root length for 24, 48, 72 and 96 h, respectively. Seeds were also sown in small poly bags in triplicates under the same temperature regimes and assayed for the physiological effects on the root, stem and leaf for 2 weeks after germination. Results showed a decrease in germination rate as temperature regimes increased. There was significant increase in the shoot length of maize at 37 and 40 degree C after 96 h of exposure to these temperature regimes but a drastic decrease at 42, 45 and 50 degree C, respectively. Root length of the maize plantlets also decreased when exposed to 45 and 50 degree C, respectively. Sorghum plantlets also showed shoot increase at 37, 40 and 42 degree C temperature regimes but decreased at 45 and 50 degree C, while root length decreased in length at 42, 45 and 50 degree C, respectively. Rice plantlets exposed to different temperature regimes showed an increase in shoot length at 37, 40, 42 and 45 degree C, respectively with a decrease only at 50 degree C and also a decrease in root length at 50 degree C. The results from the seedling experiments showed a drastic reduction in physiological parameters tested when compared with the control at p < 0.05. Root length of maize reduced from 13.10 plus or minus 1.5 at 40 degree C to 3.80 plus or minus 0.5 at 50 degree C, while length of stem of sorghum reduced from 5.00 plus or minus 0.4 to 3.40 plus or minus 0.5. Rice had a reduction in leaf length of 6.70 plus or minus 1.0 to 4.20 plus or minus 1.5. The results of the experiments also showed that sorghum was most affected by the increased temperature range among the three test crops. This study clearly indicates that the growth of maize, rice and sorghum seedlings showed signs of stagnation or decrease following rise in temperature. As temperature rise is part of the global climate change problem, the study clearly shows that climate change vis a vis increase in temperature will have strong negative implications on food crops in the nearest future especially in emerging economies like Nigeria. Key words: Cereal crops, climate change, elevated temperature, seed germination, seedling growth.