Physiological traits for improving high temperature stress tolerance in rice

High temperature stress during flowering and grain filling offsets beneficial impact of elevated CO2 on assimilate partitioning and sink-strength in rice

“…Negative impact of temperature documented on sink size and sink activity/strength (ability to utilize enhanced assimilate supply) in crop plants has instigated the need to explore crop responses to e[CO 2 ] + HT interaction under realistic environmental conditions. Previous studies quantifying e[CO 2 ] + HT interaction in rice are mostly conducted under controlled chamber conditions 15 , 27 , 29 – 31 which would not translate into delineating crop responses under realistic field conditions, due to limitation in space, light etc 33 .…”

Special Issue 2021

“…Many studies demonstrate that elevated temperature injury is caused by excessive production of reactive oxygen radicals and consequent low activities of antioxidant enzymes and membrane damage in plants (Zhang et al, 2006;Zhu et al, 2005). Plants with the ability to scavenge and/or control the level of cellular ROS may be able to withstand heat stress (Almeselmani et al, 2006;Bita and Gerats, 2013), and naturally higher levels of antioxidant enzymes in a plant may be considered as an aid to combat high temperature stress (Bahuguna et al, 2016;Ramesh et al 2017). Cao et al (2009) suggested that the relatively higher yields in heat tolerant rice genotypes under high temperature are associated with high levels of activities of ATPase and antioxidant enzymes.…”

Physiological responses of rice to increased day and night temperatures

“…Complex plant traits are strongly affected by environmental conditions, thus research findings from controlled environment conditions are sometimes different from those from natural field situations (Poorter et al, 2016). Success in breeding for heat-tolerant rice is limited, partly because it is difficult to extrapolate the findings from controlled-environment studies to the dynamics of rice response to temperature in natural environments (Bahuguna et al, 2016). Thus, it is crucial to know how rice plants perceive warmer nights in field conditions.…”

“…Recent progress in fine mapping of an effective QTL on chromosome 4 (qHTSF4.1), shows increased spikelet fertility by 15% at 38°C compared to its susceptible parent IR64 during flowering (Ye et al, 2015). However, the developed IR64 heat tolerant near-isogenic line has not been tested to assess its behaviour using a physiological approach when physiological traits related to heat tolerance are identified to be the best available useful handle for genetic improvement (Bahuguna et al, 2016).…”

“…Moreover, a significant reduction in assimilate translocation after floweringwasobservedfor the susceptible genotype when exposed to HNT (Chapter 2), highlighting the critical role high assimilate translocation plays in tolerance to HNT.In addition, net assimilate production is mainly determined by the balance between photosynthesis and respiration. Warmer nights negatively affect thebalance between day-time photosynthesis and night-time respiration (Bahuguna et al, 2016), reduce overall carbohydrate pool and biomass, and thusreduce yield(Chapter 3).The reduction in single-grain weight under HNT is related not only to the changes in source activity as reported above, but also to sink limitation resulting from the changes in enzymes involved in sucrose-to-starch metabolism (Bahuguna et al, 2016). Only superior spikelets having greater access to assimilates were considered in Chapter 5 to test if assimilate supply is the major factor leading to lower single-grain weight and poor quality under exposure to heat stress.No decline in the single-grainweight was found under HNT at early grain filling stage in the controlledenvironments.…”