粒肥施用时间对双季稻乳熟期亚细胞镉分布的影响

Effect of the application period of granular fertilizer on the subcellular cadmium distribution of doubleseason rice at the milky stage

为探究水稻生育后期施氮对双季稻乳熟期植株亚细胞镉分布及成熟期糙米镉积累的影响,开展大田试验,选取早稻株两优819(低镉积累品种)、陆两优996(高镉积累品种)和晚稻湘晚籼12号(低镉积累品种)、玉针香(高镉积累品种)为试验材料,设置3个后期施氮时期处理,分别为始穗期施氮、齐穗期施氮、灌浆期施氮,并以后期不施氮为对照。试验结果表明,后期不施氮情况下,水稻根、叶细胞镉分布表现为细胞壁>细胞液>细胞器,后期施氮处理下不同稻季根、叶亚细胞各组分镉分配比例存在较大差异,早稻品种根、叶乳熟期细胞壁和细胞液镉分配比例降低,细胞器分配比例提高,低镉积累品种株两优819根细胞壁和细胞液镉含量显著高于高镉积累品种陆两优996;晚稻品种乳熟期根、叶细胞壁和细胞液镉分配比例提高,细胞器镉分配比例降低。根细胞壁中镉分配比例与细胞器和细胞液中镉分配比例极显著负相关(P<0.01),根细胞壁镉分配比例与镉的转运系数极显著负相关(P<0.01),根细胞器中镉分配比例与镉的转运系数极显著正相关(P<0.01)。始穗期施氮,株两优819糙米镉含量显著降低28.57%;齐穗期施氮,陆两优996、玉针香糙米镉含量分别显著降低38.46%、48.15%,湘晚籼12号糙米镉含量降低10.00%;灌浆期施氮会提高糙米镉含量。水稻生育后期是籽粒镉积累的关键时期,水稻齐穗期施氮可显著降低高镉积累品种糙米镉含量。

This study aimed to investigate the effect of nitrogen application during the late growth period of rice on subcellular cadmium(Cd)distribution in double-season rice plants at the milky stage and Cd accumulation in brown rice at the maturity stage.A field experiment was conducted to select early rice plants Zhuliangyou 819(low Cd accumulation)and Luliangyou 996(high Cd accumulation),and late rice Xiangwanxian 12 hao(low Cd accumulation)and Yuzhenxiang(high Cd accumulation)as the test materials.Three nitrogen application periods during the late period were established at the initial heading stage,full heading stage,and filling stage.A treatment without nitrogen application was used as the control.The results showed that Cd distribution in the roots and leaf cells of the rice in the control treatment was cell wall>cytosol>organelle,and the Cd distribution in the root and leaf subcellular fractions of the different rice seasons differed greatly with nitrogen application.For early rice varieties,the Cd distribution ratio in the roots and leaf cell wall and cytosol at the leaf milky stage decreased and the distribution ratio of organelles increased.Cd content in the root cell wall and cytosol of the low Cd accumulating variety Zhuliangyou 819 was significantly higher than that of the high Cd accumulating variety Luliangyou 996.The Cd distribution ratio in the roots and leaf cell wall and cytosol of the late rice varieties at the milky stage increased and the Cd distribution ratio in the organelles decreased.The Cd distribution ratio in the root cell wall was negatively correlated with the Cd distribution ratio in the organelles and cytosol(P<0.01),and the Cd distribution ratio in the root cell wall was negatively correlated with the transport coefficient of Cd(P<0.01),whereas the Cd distribution ratio in the root organelle was positively correlated with the transport coefficient of Cd(P<0.01).The Cd content of brown rice was significantly decreased by 28.57%with the application of nitrogen at the initial heading stage in Zhuliangyou 819,significantly decreased by 38.46%and 48.15%with the application of nitrogen at the full heading stage in Luliangyou 996 and Yuzhenxiang,respectively,and decreased by 10.00%in Xiangwanxian 12 hao.The Cd content of brown rice was increased with the application of nitrogen at the filling stage.The late growth period of rice is a critical period for grain Cd accumulation,and nitrogen application during the full heading stage of rice can significantly decrease the Cd content of brown rice in high Cd accumulating varieties.