为探讨湘南镉污染稻区早稻的适宜收获时期,以湘早籼45号、陆两优996和株两优4026为材料,于2021-2022年在湖南郴州鎘污染稻田开展大田试验,研究了收获时期(齐穗后18、21、24、27、30d)对早稻产量与镉积累分配特性的影响.结果表明,收获时期对水稻有效穗数和穗粒数无显著影响,但结实率、千粒重和产量随收获时期推迟而提高,齐穗后27和30d处理差异不显著,但显著高于其他3个处理.随收获时期的延迟,各品种叶和谷壳镉含量、镉积累量、镉分配系数呈下降趋势,而茎和糙米镉含量、镉积累量、镉分配系数以及植株总鎘积累量呈上升趋势,除陆两优996外各品种齐穗后30 d收获处理的糙米鎘含量与积累量显著高于其他处理.水稻灌浆中后期(齐穗后18～30d)籽粒鎘主要来自土壤吸收和叶片、谷壳转运.早稻糙米镉含量品种间差异明显,陆两优996各处理糙米鎘含量均超过了国家标准(0.2mg/kg).可见,推迟收获时期有利于提高早稻产量,但籽粒镉含量也会提高,综合考虑产量和糙米镉含量,湘南镉污染稻区早稻适宜的收获时期为齐穗后27 d.
Effects of Harvest Time on Yield and Cadmium Accumulation and Distribution Characteristics of Early Rice
In order to explore the suitable harvest time of early rice in the cadmium-polluted rice area of southern Hunan,a field experiment was conducted in cadmium-polluted rice field of Chenzhou,Hunan province from 2021 to 2022 using Xiangzaoxian 45,Luliangyou 996 and Zhuliangyou 4026 as materials to study the effects of harvest time(18,21,24,27,30 days after full heading)on the yield and cadmium(Cd)accumulation and distribution characteristics of early rice.The results showed that the harvest time had no significant effect on the number of effective panicles and grains per panicle of rice,but the seed-setting rate,1000-grain weight and yield increased with the delay of harvest time.There was no significant difference between the treatments of harvesting at 27 and 30 days after full heading,but they were significantly higher than those of the other three treatments.With the delay of harvest time,the Cd content,Cd accumulation and Cd distribution coefficient in leaves and chaffs of all varieties showed a downward trend,while the Cd content,Cd accumulation,Cd distribution coefficient in stems and brown rice and the plant total Cd accumulation showed an upward trend.Except Luliangyou 996,the Cd content and accumulation in brown rice of treatmentof harvesting at 30 days after full heading were significantly higher than other treatments.In the middle and late stage of rice filling(18-30 days after full heading),the Cd in grain mainly came from soil absorption and transport of leaves and chaffs.The Cd content in brown rice of early rice varied significantly among varieties,and the Cd content in brown rice of each treatment of Luliangyou 996 exceeded the national standard(0.2 mg/kg).It can be seen that delaying the harvest time is beneficial to improve the yield of early rice,but the Cd content of grains will also increase.Comprehensively considering the yield and the Cd content of brown rice,the suitable harvest time for early rice in the Cd-polluted rice area in southern Hunan is 27 days after full heading.
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