Effects of High Night Temperature on Crop Physiology and Productivity: Plant Growth Regulators Provide a Management Option

Abstract

Crop production is experiencing both increases in the frequency and intensity of high night temperatures (HNT) (IPCC, 2007). The HNT threatens the sustainability of crop production both currently and in the future. Recent meteorological data indicated faster increases in night temperatures (NT) than day temperatures (Alward et al., 1999). Experimental evidence also indicated the importance of assessing the effects of NT separately from the day temperature, as a smaller increase in NT can show a drastic decrease in crop production (Peng et al., 2004). Studies have indicated decreased crop yields as a result of HNT (Hall, 1992; Mohammed & Tarpley, 2009a). Apart from HNT, climate change will also increase a variety of environmental stresses affecting crop production, namely heat, drought, salinity, and relative humidity, hence farming in the future climate will have to be better adapted to a range of abiotic and biotic stresses. A long-term approach to negate the effects of abiotic stress is to develop stress-tolerant cultivars. The short-term approach includes the use of agrochemicals, especially those with plant growth regulator (PGR) capabilities, for the prevention and/or amelioration of various environmental stresses, including heat stress. Studies focusing on day temperature stress and, more recently, on NT stress have increased, but, studies looking at the effects of PGR under heat stress are rare (Ashraf & Foolad, 2007). This chapter primarily focuses on the effects of HNT on crop production and the beneficial effects of PGR (glycine betaine [GB] and salicylic acid [SA]) application against heat stress on crop production with special emphasis on rice (Oryza sativa L.) production.