小麦秸秆还田量对土壤Cd有效性及水稻Cd亚细胞分布的影响

为研究小麦秸秆还田量对水稻镉(Cadmium,Cd)亚细胞分布的影响,本文采用盆栽试验的方法,研究了小麦秸秆半量(Half dose wheat straw,HDWS)、全量(Full dose wheat straw,FDWS)还田对土壤有效态Cd及水稻Cd亚细胞分布的影响。结果表明,小麦秸秆还田降低了水稻苗期与分蘖期根部细胞壁(F1)、细胞器(F2)和可溶性物质(F3)中的Cd含量(比对照降低11.0%～51.1%),但提高了灌浆期和成熟期根部F1、F2和F3中的Cd含量(10.1%～35.5%)。同时,小麦秸秆还田显著降低了灌浆期和成熟期水稻茎部F1、F2中的Cd含量(31.3%～47.4%),亦显著降低了分蘖期和灌浆期茎部F3中的Cd含量(49.4%～51.1%);HDWS和FDWS较CK均显著降低了水稻地上部分的Cd总积累量(P0.05)。小麦秸秆还田通过提高水稻根系细胞壁固定及液泡区隔化作用,显著降低了水稻稻谷中Cd含量,降低了Cd的食品安全风险。根据研究结果,小麦秸秆全量还田更有利于Cd污染土壤上水稻安全生产,且DGT法评估水稻Cd有效性优于化学提取法。

Effects of returning wheat straw on available cadmium and subcellular distribution of cadmium in rice

The effects of wheat straw returning treatments on distribution of cadmium subcellular in rice were studied by a pot experiment for providing a scientific basis of straw returning at Cd polluted area. The different straw returning treatments were 7 850 kg·hm^-2(FDWS), 3 925 kg·hm^-2(HDWS)of wheat straw and CK with no straw returning. The soil available Cd and the distribution characteristics of Cd in rice subcellular structures were studied. The results showed that wheat straw returning treatments decreased the Cd contents in the cell wall (F1), organelles(F2), and soluble matter(F3)of rice roots(by 11.0%~51.1% compared to the CK)at the seedling and tillering stages, while the Cd content was increased in the F1, F2, and F3 of rice stems(by 10.1%~35.5%)at the filling and mature stages. Meanwhile, the results showed that wheat straw returning significantly reduced the Cd content in the F1 and F2 of rice stems(by 31.3%~47.4%)at the filling and mature stages, and also reduced the Cd content in the F3 of rice stems (49.4%~51.1%)at the tillering and filling stages. When compared HDWS and FDWS with CK, both straw returning treatments remarkably decreased the total accumulation of Cd in shoots(P<0.05). Cell wall binding and vacuolar compartmentalization were very important Cd detoxification mechanisms in rice roots, and Cd transportation from roots to shoots was restricted by wheat straw returning, which also significantly lessened the Cd content of rice grains, thus reducing the food safety risks resulting from Cd. Based on the above results, the FDWS treatment is recommended to safely produce rice in Cd-polluted soils, and correlation analysis revealed that the diffusive gradients in thin-films(DGT)may be a better indicator than traditional chemical extractants at reflecting the bioavailability of Cd in soils.