Objective The study analyzed the spatial distribution of polyamines in high-quality indica rice grains. The response of spraying of putrescine and spermidine were revealed in two fragrant rice varieties.

Method Field experimental methods were used to collect the grains of high-quality rice varieties 'Huanghuazhan' (HHZ) 'Meixiangzhan 2' (MXZ2), and 'Xiangyaxiangzhan' (XYXZ) under the same cultivation conditions. The putrescine, spermidine, and spermine were determined by HPLC in brown rice, polished rice, and embryos, respectively. Exogenous spraying of putrescine and spermidine was applied to the young panicles of MXZ2 and XYXZ. The polyamines, 2-acetyl-1-pyrroline (2-AP), and rice taste value were detected in grains.

Result The putrescine, spermidine, and spermine can be detected in all brown rice, polished rice, and embryo of three indica rice grains. The total content of polyamines was similar in each part, and the content of polyamines in polished rice is about half of that in brown rice, with the highest concentration of polyamines in the embryo. The content of spermine, putrescine, and spermidine decreased sequentially. The content of polyamines was significantly increased in XYXZ, with the spermine increased by 51.3%. There was no significant change in the content of polyamines in MXZ2 grains with spraying putrescine or spermidine. Exogenous polyamine treatment can both increase the 2-AP content of MXZ2 and XYXZ, under spermidine treatment, the 2-AP content increased by 6.8% and 6.1%, respectively. After treatment with putrescine, the eating quality value and taste value of MXZ2 increased by 2.2% and 2.8%, respectively.

Conclusion The content and distribution characteristics of polyamines were similar in brown rice, milled rice and embryo of high quality indica rice grains. The relative concentration of polyamines in embryo was the highest, while the spermine content was the highest in grains. Both exogenous putrescine and spermidine can enhance the 2-AP content and improve the eating quality of rice.