Bt玉米光合作用和生长性状的变化

在华南地区种植美国先锋公司的Bt玉米34824与其非转基因近等基因系34823，比较它们的光合作用和部分重要的生理生长性状。结果表明，Bt玉米由于Bt基因的插入和表达使植株得到保护，受玉米螟危害的叶片显著减少；但Bt玉米植株的光合作用和部分生理生长性状也发生了一定的变化。与其非转基因近等基因系34823相比，虽然Bt玉米34824的胞问CO2浓度变化不大；并且在绝大多数生长时期，Bt玉米的蒸腾速率和气孔导度大于的非转基因玉米；但是从生长中期始，Bt玉米的净光合速率却一直小于非转基因玉米，在生长后期，这种差异甚至达到显著水平。在生长性状方面，各时期观察到的Bt玉米植株叶片数一直略少于非转基因玉米，表明Bt玉米的生长发育受到一定的延缓。同时，Bt玉米植株的株高变矮，单株叶面积变小，根系活力显著降低。在地下部，Bt玉米34824的植株根系总长度、根总表面积、根总体积和平均根直径均小于相对应的非转基因近等基因系34823。

Change of photosynthesis and growth of Bt corn

Bt corn is one of the large-scale commercialized GM crops being planted around the world.The debate surrounding the potential ecological risk of Bt corn is ongoing.Among these there are concerns over the photosynthesis and growth properties of corn hybrids with the Bt trait transferred from Bacillus thuringiensis.In order to learn the behave of transgenic Bt corn in South China a plot experiment was conducted in a greenhouse in South China Agricultural University.The experiment compared the photosynthesis and some growth characteristics of Bt corn 34B24 with its non-transgenic near isogenic line 34B23.From the experiment it can be found that because of the expression of Bt gene,Bt corn had no leaves damaged by corn borer(Ostrinia nubilalis) while its non-transgenic counterpart had many leaves damaged by corn borer.But Bt corn plant was also found some physiological and ecological changes.The difference of the internal CO_2 concentration between Bt corn 34B24 and its near isogenic line 34B23 was not significant.In most stages Bt corns had higher transpiration rate and leaf stomatal conductance.In the late stage,the differences of transpiration rate and leaf stomatal conductance between 34B24 and 34B23 were significant.But the net photosynthesis rate of Bt corn 34B24 was smaller than that of 34B23,and in the late stage the difference was significant.Bt corn plant had slightly delay for the growth and development.Bt corn 34B24 were found slightly less leaves than its conventional near isogenic line 34B23 at every observation.Bt corns also had shorter plant height,smaller leaf area than 34B23.As to the underground property,Bt corn 34B24 had decreased root vigor.34B24 also had less total root length,total root surface area,and average root diameter than its near isogenic line 34B23.