Abstract
The pot experiment with three treatments of nitrogen (N) topdressing was performed with the japonica rice cultivar viz. Huaidao 5. Remobilization of nine mineral nutrients including N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) was measured from the source organs including bracts, leaf, and sheath to sink rice grain. Experimental results showed considerable contribution of bracts to grain for N, Mg, and Zn, with the averages contributions of 5.96, 12.56, and 12.34%, respectively, indicating a positive role of rice bracts in N, Mg, and Zn remobilization during grain filling. By contrast, minor contribution of bracts to grain P, K, and Cu was revealed, with the contribution rate being 0.99, 3.90, and 3.05%, respectively. Further, a net increase in Ca and Fe concentrations of bracts was detected, implying that bracts function as a sink of these mineral nutrients. In addition, grains produced at a moderate level of N topdressing had higher Fe and similar Zn concentration in comparison with those at high N level, suggesting the possibility of N management for maintaining Fe and Zn level under high yielding conditions.
Highlights
Mineral elements occupy an essential role in human nutrition (Huang et al 2016)
Dry matter in bracts was slightly lower at 35 DAA than at 7th day after anthesis (7 DAA) (Table 1), indicating the translocation of assimilates in these organs
This study quantified the contribution of rice bracts to grain in terms of minerals, and examined the effect of nitrogen topdressing
Summary
Mineral elements occupy an essential role in human nutrition (Huang et al 2016). Deficiencies of micronutrients like zinc (Zn) and iron (Fe), recognized as hidden hunger, are the most prevalent health disorders worldwide, affecting nearly two billion people (Promchan et al 2016). Rice is a major staple crop, supplying the bulk of calories and the majority of daily dietary nutrients for billions of people (Cakmak 2008; Waters et al 2009). Enrichment of the staple crops like rice with essential nutrients, especially Zn and Fe, is currently a high-priority research area in crop science. Flag and upper leaves are the main source organs of assimilates and mineral nutrients for grain filling (Sperotto et al 2009; Zhang et al 2017). Non-leaf organs such as stems, branches, sheaths, glumes/bracts, and awns have chloroplasts and photosynthetic activities,
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