growthrooms,onemightexpectthemoredynamicenvironment of the field to elicit an even stronger response of the Rca-Oa recombinantprotein. The choice of 45◦C as an appropriate temperature to heat stress rice with abundant water supply was evident in that the data reveal no impact of heat on growth and development traits, including yield until daily maxima were raised to 45◦C. It should be noted that leaf temperatures were 2–3◦C lower than air temperature, suggesting that the threshold leaf temperature for heat-induced damage to photosynthetic biochemistry was between 38 and 42◦C. This temperature threshold accords with our previous in vitro findings, where temperatures greater than 36◦C severely impaired function of Rca-Os while having little effectonRca-Oa.Inthistemperaturerange, the advantageous effect of Rca-Oa expression at levels below 20% of the total Rca complement was sufficient to enhancevegetativegrowth,finalbiomass,panicledevelopmentand,most particularly,seednumber.Becausethegraindevelopedoptimally inallplantsat30◦C,variationinyieldisreflectedinseednumber (Yoshida,1981;Yoshidaetal.,2006;Makino,2011;Sánchezetal., 2014).Aswellashigherseednumbers,thereisalsoevidencethat seedsetwaspositivelyaffectedbyRca-Oaexpression,supporting