It is concluded that projected CO2 in 2050 may have larger effects on rice grain quality than the projected temperature increase. Although deterioration in milling suitability, grain appearance and nutritional quality can be expected, the taste of cooked rice might be better in the future environment. © 2015 Society of Chemical Industry.

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With the trends of global warming, the extreme high temperature stress often happens during crop grain filling in the world. Heat stress has been an important factor limiting grain yield and quality. To determine the effects of heat stress on fresh kernel yield, quality and enzyme activities of sucrose metabolism, we carried out an experiment in artificial phytotron using two sweet corn cultivars (Xiatian 1 and Yuetian 16) with two typical temperature treatments (high temperature, HT and control, CK) during grain filling. The results indicated that the growth process of sweet corn was accelerated, but the weight and quality of kernel was decreased seriously under high temperature. The weight of 100-fresh-kernel and kernel water content were markedly reduced, but content of pericarp was increased. At the optimum harvest stage of fresh ear (with kernel water content 68%-74%), the fresh kernel weight of the two cultivars was reduced significantly by 20.8% (Xiatian 1) and 16.4% (Yuetian 16) under higher temperature respectively. The contents of soluble sugar and sucrose first increased and then decreased during the grain filling stage. High temperature was not favorable to sugar accumulation, resulting in sucrose content decrease and starch content increase. Sucrose phosphate synthetase (SPS) and sucrose synthetase (SS) play an important role in sucrose synthesis and degradation. SS catalyzes the interconversion of sucrose. Heat stress decreased the activities of SPS and SS (synthetic) and increased the activity of SS (cleavage), which inevitably leads to a depression in sucrose content and a reduction in kernel quality. The maximum SS (synthetic) activity in process of grain filling of two sweet corns appeared earlier under high temperature, while that of SPS activity appeared earlier in Xiatian 1 and did not in Yuetian 16.

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Maize (Zea mays L.) contributes approximately 55% of China’s grain production. The effects of nitrogen (N) on maize grain morphology and starch granules remain elusive. In this study, a field experiment in clay loam soil was conducted using three maize hybrids (Suyu 30, Suyu 20, and Suyu 29) and four N levels (0, 360, 450, and 540 kg ha−1) in 2010 and 2012. The results indicated that increased grain length and width, starch granule number, surface area, and volume, was associated with the application of 450 kg ha−1 of N. Differences between superior (ear base) and inferior (apical) grains decreased under highest yield treatments. The effects of N levels on inferior grains was more than that on superior grains. The starch granules of superior grains showed more polygonal, and bigger shape than inferior grains. The results revealed that N levels affected size and morphology of starch granules and grains. The application of 450 kg N ha−1 resulted in larger-sized starch granules and less difference between superior and inferior grains.