摘要
转基因棉花对中国和世界棉花生产起到了积极的推动作用。随着转Bt CrylAc基因棉花的种植面积逐年增加,人们对转基因作物释放后存在的安全性也越来越关注。因此深入研究转Bt基因抗虫棉在土壤中的Bt毒蛋白含量与残留、对土壤生态系统平衡、酶活性等的影响是转基因作物能否健康、可持续发展的必备条件。
本试验采用盆栽试验并结合酶联免疫(ELISA)法测定了转Bt基因抗虫棉及常规棉花在不同生育时期在根际土壤及非根际土壤的Bt毒蛋白含量,以及各个生育时期的根际及非根际土壤的脲酶和蔗糖酶活性变化,旨在为转Bt基因棉花种植后的根际环境变化提供信息,并为转基因植物的土壤生态系统安全性评价提供科学依据。
主要结果如下:
1.红壤、黄棕壤及黄褐土种植转Bt基因棉花和常规棉花后,根际土的Bt毒素含量大于非根际土的,其中转Bt基因棉花根际土与非根际土有显著性差异,而常规棉花根际与非根际则差异不显著。转Bt基因棉花在苗期根际土的Bt毒素含量为黄褐土＞黄棕壤＞红壤,分别为常规棉花根际土的1.44、1.21、2.38倍,而在花铃期为黄棕壤＞黄褐土＞红壤,分别为常规棉花根际土的1.56、1.16、1.97倍,且均达到显著差异。
2.黄褐土、黄棕壤和红壤两种棉花的根际土和非根际土都随棉花生长期增长Bt毒素含量先增加后减少。其中转Bt基因棉花的黄褐土、黄棕壤和红壤根际土的Bt毒素含量最大值分别为3.67 ng/g土、3.61 ng/g土和3.16 ng/g土,而最小值分别为0.79 ng/g土、0.79 ng/g土和0.62 ng/g土。在实验期间内,转Bt基因棉花的根际土Bt毒素含量大于常规棉花的,说明转Bt基因棉花确有更多的Bt毒素释放到根际土中。
3.黄褐土、黄棕壤和红壤上种植转Bt基因棉花或常规棉花后,根际土的蔗糖酶活性高于非根际上。蕾期、花铃期的转Bt基因棉花根际土的蔗糖酶活性均为黄棕壤＞黄褐土＞红壤,且都达到显著差异。转Bt基因棉花蕾期黄棕壤、黄褐土及红壤根际土的蔗糖酶活性分别是常规棉花根际土的0.93、1.14、1.02倍,花铃期为1.09、1.07、1.24倍。
4.黄褐土和黄棕壤根际土和非根际土的蔗糖酶活性均随生长期先减小再增大,最后又减少。其中种植转Bt基因棉花的黄褐土和黄棕壤根际土的蔗糖酶活性最小值分别为28.17 mg/g土和39.00mg/g土,而最大值分别为50.36 mg/g土和63.68 mg/g土。
5,转Bt基因棉花蕾期根际土的脲酶活性为黄棕壤＞红壤＞黄褐土,但相互间差异不显著,而在花铃期为黄褐土＞红壤＞黄棕壤,且黄褐上与红壤有显著差异,红壤与黄棕壤差异不显著。转Bt基因棉花根际土的脲酶活性都大于非根际土。转Bt基因棉花蕾期黄褐土、黄棕壤和红壤根际土的脲酶活性分别是常规棉花根际土的2.02、1.87、2.31倍,花铃期为0.96、0.88、1.01倍。
6.从蕾期到吐絮期,转Bt基因棉花的根际土和非根际土以及常规棉花的非根际土的脲酶活性一直减小,而常规棉花根际土的脲酶活性则先增大,后减小。其中转Bt基因棉花的黄褐土和黄棕壤的根际土脲酶活性最大值为分别为0.82 mg/g土和0.87mg/g土,而最小值分别为0.59 mg/g土和0.41 mg/g土。整个生育期内,根际土的脲酶活性均大于非根际土的。
Transgenic cotton has played a pc,sitive role in promoting cotton production of China and the world.With the growth of planting area of the transgenic Bt CrylAc cotton year by year,people pay more attention to the safety of the release of transgenic crops.Deeply study of the Bt toxic protein content and residue in the soil after planting transgenic Bt cotton and non-Bt cotton,and the influence on the soil ecosystem balance and the soil invertase and urease activity are necessary conditions for sustainable development and healthy of Transgenic crops.
Detecting content of Bt insecticidal crystalline protein(ICP) using the enzyme linked immuno sorbed assay(ELISA),the invertase activity and urease activity in rhizosphere and non-rhizosphere soil in different stages of transgenic Bt cotton and non-Bt cotton adopt a pot experiment,that can provide the effects of rhizosphere environment and a scientific basis for safety assessment of the soil ecosystem.The main results are outlined as follows:
1.Content ofBt ICP in rhizosphere soil is more than in non-rhizosphere soil after planting transgenic Bt cotton and non-Bt cotton.Content of Bt ICP in bud stage of transgenic Bt cotton in rhizosphere soil is in the order of yellow cinnamon soil＞yellow brown soil＞red soil.Contents ofBt ICP oftransgenic Bt cotton were 1.44,1.21 and 2.38 times of non-Bt cotton in yellow cinnamon soil,yellow brown soil and red soil,separately. Content of Bt ICP in flowering and boll-setting period of transgenic Bt cotton in rhizosphere soil is in the order of yellow brown soil＞yellow cinnamon soil＞red soil. Contents of Bt ICP of transgenic Bt cotton were 1.56,1.16 and 1.97 times of non-Bt cotton in yellow brown soil,yellow cinnamon soil and red soil,separately.All of them are significantly differences.
2.Content of Bt ICP of transgenic Bt cotton and non-Bt cotton in rhizosphere and non-rhizospher soil firstly increases,then decreases with time.The maximum values of Bt content of transgenic Bt cotton in rhizosphere soil are 3.67 ng/g in yellow cinnamon soil, 3.61 ng/g in yellow brown soil and 3.16 ng/g in red soil.And the minimum values of Bt content are 0.79 ng/g in yellow cinnamon soil,0.79 ng/g in yellow brown soil and 0.62 ng/g in red soil.Throughout the experimental period,content ofBt ICP in rhizosphere soil of transgenic Bt cotton is approximately more than of non-Bt cotton.The result show that more Bt ICP released to rhizosphere soil from transgenic Bt cotton than non-Bt cotton.
3.The soil invertase activity in rhizosphere soil is approximately more than in non-rhizosphere soil after planting transgenic Bt cotton and non-Bt cotton.The soil invertase activity of transgenic Bt cotton in rhizosphere soil including bud stage and flowering and boll-setting period is in the order of yellow brown soil＞yellow cinnamon soil＞red soil.All of them are significantly differences.The soil invertase activity of transgenic Bt cotton in bud stage is 0.93 times of non-Bt cotton in yellow brown soil,1.14 times in yellow cinnamon soil and 1.02 times in red soil.And when in flowering and boll-setting period,that is 1.09 times,1.07 times and 1.24 times.
4.The soil invertase activity of transgenic Bt cotton and non-Bt cotton in rhizosphere and non-rhizospher soil including yellow brown soil and yellow cinnamon soil firstly decreases,then increases with time.The minimum soil invertase activity of transgenic Bt cotton in rhizosphere soil are 28.17 mg/g in yellow cinnamon soil and 39.00 mg/g in yellow brown soil.And the maximum values of Bt content are 50.36 mg/g in yellow cinnamon soil and 63.68 mg/g in yellow brown soil.
The soil urease activity of transgenic Bt cotton in rhizosphere soil in bud stage is in the order of yellow brown soil＞red soil＞yellow cinnamon soil.And they are no significant differences.And the soil urease activity in flowering and boll-setting period is in the order of yellow cinnamon soil＞red soil＞yellow brown soil.
5.It is significantly difference between yellow cinnamon soil and red soil.It is no significantly difference between red soil and yellow brown soil.The soil urease activity in rhizosphere soil is more than in non-rhizosphere soil after planting transgenic Bt cotton. The soil urease activity of transgenic Bt cotton in bud stage is 2.02 times of non-Bt cotton in yellow cinnamon soil,1.87 times in yellow brown soil and 2.31 times in red soil.And when in flowering and boll-setting period,that is 0.96 times,0.88 times and 1.01 times.
6.The soil urease activity of transgenic Bt cotton and non-Bt cotton in non-rhizosphere soil decreases with time.And the soil urease activity of transgenic Bt cotton in rhizosphere soil is similar to that.The soil urease activity of non-Bt cotton in rhizospher soil firstly increases,then decreases.The maximum soil urease activity of transgenic Bt cotton in rhizosphere soil are 0.82 mg/g in yellow cinnamon soil and 0.87 mg/g in yellow brown soil.And the minimum values of Bt content are 0.59 mg/g in yellow cinnamon soil and 0.41 mg/g in yellow brown soil.Throughout the experimental period,the soil urease activity in rhizosphere soil is more than of in non-rhizosphere soil.
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