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1、Effect of Bt Cotton on Enzymes Activity and Microorganisms in Rhizosphere,Bt棉花对根际土壤酶活性和土壤微生物的影响 Usha Mina、Anita Chaudhary、Anju Kamra Journal of Agricultural Science（2011）,Outline,1 Introduction2 Materials and methods 2.1 Field preparation and cultural practices 2.2 Soil Sampling 2.3 Dehydrogenase、Al
2、kaline phosphatase、Urease、Nitrate reductase activity 2.4 Nematodes（线虫）、Collembola（弹尾目）and Ants3 Results and discussion,1 Introduction,In India nine million hectares(m ha)area was under cotton cultivation and it is one fourth of the global area under cotton cultivation.Bacillus thuringiensis(Bt)cotto
3、n was introduced in India in 2002.Following its success,during the last 7 years(2002-2008),the area under Bt cotton has increased by 7.6 m ha from 0.029 m ha.在印度棉花的种植面积达九百万公顷，占全球棉花种植面积的四分之一。印度在2002年引进苏云金芽孢杆菌(Bt)棉。在过去的7年(2002-2008)，种植面积从29万公顷增加到760万公顷。James,2008,Although there are diverse benefits of
4、 Bt cotton,public concern also exist because both in vitro and in vivo studies on Bt cotton showed that Bt toxin produced in leaves,stems and roots of Bt cotton plants is introduced in soil.,通过对Bt棉体外和体内的研究表明，Bt棉花在叶片、茎和根部产生Bt毒素并释放到土壤中。,Bt-toxin from Bt cotton plants introduced into the soil through t
5、wo pathways,i.e.,biomass incorporation and root exudates.,Bt毒素通过两条途径从Bt棉花植物体释放到土壤，例如，生物量合成和根分泌物。,Saxena and Stotzky 2001 Mina et al.,2008 Liu 2009,Bt toxin released in soil get adsorbed or bound on clay particles,humic components,or organic mineral complexes and then be protected against degradation
6、 by soil microorganisms(Tapp et al.,1995).,释放到土壤中的Bt毒素被粘土颗粒、腐植酸或有机矿物复合体吸附或束缚,防止其被土壤微生物降解。,Continuous growing of Bt crops on same location enhance its existing levels to a certain concentration that might affect the composition and activity of soil microbial communities(Donegan and Seidler 1999;Stotz
7、ky 2004;Wei et al.,2006)and the soil biochemical.,在同一地点连续种植Bt作物其浓度就会增加，当达到某一定浓度时就有可能影响土壤微生物群落的组分和活动以及土壤的生物化学特性。,Some studies indicate that Bt cotton has no negative effects on soil flora and fauna and may even have beneficial effects(Saxena and Stotzky 2001;Sarkar et al.,2009)，while some have report
8、ed adverse effects(Cui and Xia 2000;Tan et al.,2002).,一些研究表明Bt棉花不会对土壤植物和动物造成负面影响,甚至可能产生有益作用，同时也有一些不良影响的报导。,Therefore,we have studied the effects of Bt cotton(var.Mech 162)on activity of soil enzymes and microorganisms at Indian Agriculture Research Institute farms,New Delhi,India.An evaluation of th
9、e ecological risks of Bt cotton was made on the basis of changes in enzymes activity and number of nematodes,collembola and ants as compared to non Bt cotton in the respective rhizospheres.,因此，我们研究印度农业研究所农场、新德里、印度的Bt棉花对土壤酶活性和土壤微生物的影响。针对Bt棉花和非Bt棉花的植物根际酶活性变化量和线虫、弹尾目昆虫和蚂蚁的数量变化进行生态风险评价。,2 Materials and
10、methods,2.1 Field preparation and cultural practices Field experiments were conducted at the research farm of the Indian Agricultural Research Institute,New Delhi,India.田间试验布置在印度的农业研究所的农场、新德里、印度。Experiments were conducted for three consecutive years(2004,2005 and 2006)in a large plot(450 m2)where Bt
11、 and non Bt cotton had ever planted.This plot was subdivided into 24 subplots(3.75m x 5m).在常年种植Bt和非Bt棉花的土壤上进行了三年(04、05、06年)的连续试验，总面积为450m2，分为24个小区(3.75m5m)。,Treated:seeds of non Bt cotton and Bt cotton.Distance between row to row and plant to plant:60 cm and 45 cm respectively.Buffer zone:A 6 m also
12、 established surrounding the main plot.Recommended dose of NPK fertilizer:660 g N as Urea,250 g P as SSP,350 g K as MOPApplied time:phosphorus and Potash was applied at time of sowing,whereas nitrogen was given in split dose,half at the time of thinning and other half at flowering stage.Irrigate tim
13、e:First irrigation to cotton was given one week after sowing and subsequent irrigations at an interval of two weeks.Harvest time:in the first week of December in all the three years,2.2 Soil SamplingSoil samples from the rhizosphere of Bt cotton and non Bt cotton plants were collected at regular int
14、erval(30days interval,coinciding with different growth stage of cotton)since the date of sowings till harvesting in all the three years.Bt棉花和非Bt棉花根际土壤样品在整个三年内都是自播种之日起有规律间隔采集的(30天间隔,正好与棉花不同生育期相符合)。,2.3 Dehydrogenase、Alkaline phosphatase、Urease、Nitrate reductase activity,Measured using UVVis spectroph
15、otometer(UV-1201,Shimadzu Corp,Japan)紫外可见光谱分光光度计,2.4 Nematodes（线虫）、Collembola（弹尾目）and Ants,Nematodes:从水里提取后用立体解剖显微镜计数,Collembola and Ants：用干漏斗提取后用立体解剖显微镜计数,3.Results and discussion,On average dehydrogenase,alkaline phosphatase,nitrate reductaase and urease enzymes activity was high in Bt cotton rhiz
16、osphere as compared to non Bt rhizosphere.,On comparing enzymes activity for the interaction of crop variety(Bt and non Bt trait)over a monthly period,activity of dehydrogenase and urease enzymes were non significant and activity of Phosphates and nitrate reductase enzymes were significant.,总体来讲，与非B
17、t棉花根际土壤相比，Bt棉花根际土壤的脱氢酶、碱性磷酸酶、硝酸还原酶和脲酶活性较高。,在比较作物品种(Bt和非Bt特质)相互作用的酶活性超过一个月后，脱氢酶和脲酶活性都没有较大变化，而磷酸酶和硝酸还原酶有显著的变化。,Figure 1.Variations in activity of(a)Dehydrogenase(b)Alkaline phosphatase(c)Nitrate reductase and(d)Urease enzymes at different growth stages in Bt and Non Bt cotton rhizosphere,Except dehydr
18、ogenase enzyme,differences in activity of alkaline phosphatase,nitrate reductase and urease enzymes between Bt and non Bt plants rhizosphere were statistically non significant.Over the crop growth period(of 150 days)the activity of Phosphatase,nitrate reductaase and urease enzymes activity was high
19、in the rhizosphere at early vegetative and flowering stage,whereas activity of dehydrogenase enzyme was high at boll formation stage.Activity of all the four enzymes declined at crop harvesting stage.,除了脱氢酶以外，碱性磷酸酶、硝酸还原酶和脲酶活性在Bt和非Bt棉花根际之间的差异不显著。作物生长期间(150天)，磷酸酶、硝酸还原酶和脲酶活性在早期营养生长和开花阶段较高，脱氢酶活性则在铃形成阶段较
20、高。四种酶在作物收获阶段活性都会降低。,Study demonstrated enhanced phosphatase,nitrate reductase and urease activity in the rhizosphere of Bt cotton,but most of the time differences in enzymes activity between Bt and non-Bt cotton rhizosphere were non significant.,有研究证实Bt棉花根际土壤的磷酸酶、硝酸还原酶和脲酶活性增强，但大部分时间里，Bt棉和非 Bt 棉根际酶活性
21、之间的差异并不显著。,In present study variation in dehydrogenase enzyme activity between Bt and non-Bt cotton rhizosphere was significant(P0.05)and activity of dehydrogenase enzyme was high in Bt cotton rhizosphere.,目前的研究表明，非Bt棉和Bt棉花之间根际土壤脱氢酶活性变化是显著的(P 0.05)，Bt棉花根际土壤的脱氢酶酶活性高于非Bt棉。,The enhancement in activity
22、of dehydrogenase in Bt cotton rhizosphere may be due to altered composition of its root exudates.Root exudates have a profound qualitative and quantitative effect on the rhizospheric microorganisms.Bt棉花根际土壤的脱氢酶活性增强可能是由于其根际分泌物成分的变化。根际分泌物对于微生物的组成起着重大的定性和定量的作用。,Schenck,1976,Table 4.Number of nematodes,
23、collembola,ants in Bt and non Bt cotton rhizosphere,Significant differences(P0.05)were observed in the number of nematodes,collembola and ants between the Bt and non Bt cotton rhizosphere(Table 4).Number of nematodes,collembola and ants were more in Bt plants rhizosphere as compared to non Bt plants
24、 rhizospere.Number of nematodes,collembola and ants were highest in Bt and non Bt cotton rhizosphere at flowering stage.研究发现Bt棉花和非Bt棉花根际的线虫、弹尾目昆虫及蚂蚁数量（表4)有显著差异(P 0.05)。与非Bt棉花相比，Bt棉花根际的线虫、弹尾目昆虫和蚂蚁数量更多。Bt和非Bt棉花这三者的数量均在开花阶段达到最高。,Temporal variation in number of nematodes,collembola and ants is a complic
25、ating factor in impact assessment of Bt transgenic cotton,because the impact of the genetic modification may be transient and minor compared to the variation caused by soil condition and growth stage of crop.,线虫、弹尾目昆虫和蚂蚁数量的时间变化在Bt转基因棉影响评价中是一个复杂因素，因为与土壤条件和作物的生长阶段带来的变化相比，基因转变的影响可能是短暂的、微小的。,However the
26、se results should be considered as preliminary,as nematodes,collembola and ants are mobile and slight change in their niche environment may affect their mobility.,然而,这些结果应该认为是初步的，因为线虫、弹尾目昆虫和蚂蚁是移动的，生态位环境的轻微改变也将影响他们的移动性。,In general,we speculate that effects of Bt cotton on the number of nematodes,coll
27、embola and ants in rhizosphere might mainly depend on the extent of change in root exudates(quality and/or quantity)that may related to variety differences.我们可以推测Bt棉花对根际土壤线虫、弹尾目昆虫和蚂蚁数量的影响可能主要取决于与品种差异相关的根际分泌物的的改变程度(质量/或数量)。,In conclusion,based on three year field experiments it was found that Mech 16
28、2 variety of Bt cotton has no adverse effect on soil biochemical and microbial indicators.The differences caused by growing Bt cotton were not as large as those resulting from seasonal changes indicating that effect of Bt cotton on soil ecology was within normal variation expected in conventional agriculture.总之，三年的田间试验结果表明Bt棉花对土壤生化和微生物指标没有不利影响。由种植Bt棉花引起的差异与季节变化相比并不是很大，这表明Bt棉花对土壤生态系统的作用如传统农业的期望在正常变化之内。,Thanks for your time!,
