JIA-2018-09

1989 TAO Zhi-qiang et al. Journal of Integrative Agriculture 2018, 17(9): 1979–1990 (Blumenthal et al . 1991; Zhang et al . 2012). Furthermore, extreme heat can reduce the function of chlorophyll enzymes, which can limit availability of sugar and energy for seed growth (Wahid et al . 2007). Therefore, exposure to HTS at D20 may have reduced the photosynthetic rate, and subsequently, caused the reduction in grain weight and increase in protein content. Higher temperatures can also cause wheat to mature faster, which can shorten the grain filling period (Akter and Islam 2017). Thus, grain weight was reduced, the grain nitrogen content was increased, and the grain protein content was increased correspondingly (Jenner et al . 1991; Liu et al . 2007). 4.3. Response of wheat grain production and flour quality to zinc fertilizer and high temperature stress The type of wheat (strong gluten or medium gluten wheat) is dependent upon grain quality and its end use. Wheat with high protein content for bread is considered strong gluten and wheat with a lower protein content for slender and steamed bread is considered a medium gluten wheat. Certain varieties of wheat are better for particular food uses depending on the flour quality. Bread wheat has high protein content and strong gluten strength, noodle wheat has a moderate protein content and gluten strength, and biscuit wheat has a low protein content and gluten strength (Shewry et al . 1997). HTS increased grain protein content in both cultivars, but reduced grain weight and protein yield (Liu et al . 2007). The results of this study also showed that additional zinc fertilizer reduced the extent of grain weight loss in HTS-treated plants of both cultivars (Fig. 2), and zinc fertilizer significantly ( P <0.05) increased grain protein content and protein yield of both wheat cultivars. Furthermore, compared with ZM8 under HTS, grain protein content of GY2018 was significantly higher (Figs. 5 and 6). The high protein content of GY2018 makes it a high quality wheat that is suitable for bread-making; whereas, the lower protein content of ZM8 makes it a lower quality wheat that is more suitable for noodle-making. The glutenin content and the ratio of glutenin to gliadin of strong gluten GY2018 was significantly higher than that of medium gluten ZM8. Compared with the Zn0 treatment under HTS, Zn treatments increased glutenin content, gliadin content, and the ratio of glutenin to gliadin. These changes suggest that the content of the main storage proteins of wheat flour also increased. Higher amounts of storage protein increases gluten strength where greater strength indicates a better processing quality of flour, and GY2018 is a prime example of a strong gluten wheat. These results showed that application of 15 mg Zn kg –1 soil zinc fertilizer to plants under HTS is beneficial to improving the processing quality of flour in strong gluten wheat GY2018 and medium gluten wheat ZM8. Zinc addition is especially beneficial to GY2018 because it alleviated some of the negative effects of HTS on grain weight and grain yield. 5. Conclusion The addition of zinc fertilizer increased grain yield and weight, positively affected NR and GS activities within days but not weeks after anthesis, and affected grain protein yield, content and components (glutenin, gliadin, abumin, and globulin). High temperature stress reduced grain yield and weight and NR and GS activities but increased grain protein content. HTS also decreased grain protein yield and likely affected the synthesis of protein components. Zinc fertilizer and high temperature stress had different effects on different wheat cultivars. Zinc fertilizer appears to alleviate the negative effects of high temperature stress on wheat yield and flour quality. The results of this study may be helpful to farmers seeking ways to increase their grain yield while maintaining grain quality in light of the potential threats to plant growth from climate change. Acknowledgements This study was supported by the National Key Research and Development Program of China (2016YFD0300407) and the earmarked fund for the China Agriculture Research System (CARS-03). References Akter N, IslamM R. 2017. Heat stress effects and management in wheat. A review. Agronomy for Sustainable Development , 37 , 1–17. Asseng S, Ewert F, Martre P, Rotter R P, Lobell D B, Cammarano D, Kimball B A, Ottman M J, Wall G W, White J W, Reynolds M P, Alderman P D, Prasad P V V, Aggarwal P K, Anothai J, Basso B, Biernath C, Challinor A J, Sanctis GD, Doltra J, et al . 2015. Rising temperatures reduce global wheat production. Nature Climate Change , 5 , 143–147. Blumenthal C S, Barlow E W R, Wrigley C W. 1993. Growth environment and wheat quality: The effect of heat stress on dough properties and gluten proteins. Journal of Cereal Science , 18 , 3–21. Blumenthal C S, Bekes F, Batey I L, Wringely C W, Mass H J, Mares D J, Barlow E W R. 1991. Interpretation of grain quality results from wheat variety trials with reference to higher temperature stress. Australian Journal of Agricultural Research , 42 , 325–334. Crawford N M. 1995. Nitrate: Nutrient and signal for plant growth. The Plant Cell , 7 , 859–868. FAO. 2017. FAOSTAT, Food and Agriculture Organisation of the United Nations, Rome. [2017-09-22]. http://faostat.fao .