施氮肥对盐胁迫下Bt棉生长和叶片Bt蛋白含量的影响

 以Bt棉品系K638为材料，在盆栽条件下研究了施氮肥对不同程度盐胁迫（土壤含盐量：0(CK)、0.15%(轻度胁迫)和0.3%（中度胁迫））下棉株生长、氮素吸收、Bt蛋白含量和Bt蛋白氮占全氮量比例的影响；同时，在水培条件下研究了不同形态氮素（硝态氮和铵态氮）对NaCl胁迫下Bt蛋白含量的效应。结果表明，氮肥与盐胁迫对棉叶Bt蛋白含量有显著的互作效应。非盐和低盐胁迫下，施氮肥促进了棉株生长（生物量分别提高了3.0和2.8倍）、Bt蛋白合成（分别提高41.0%和90.9%）和全N向Bt蛋白N的转化（分别提高9.3%和15.6%）；中度盐胁迫下，施氮肥虽也促进了棉株生长（1.4倍），并提高了叶片全N含量（98.8%）和Bt蛋白含量（83.3%），但并未提高Bt蛋白N占全N量的比例。无论盐胁迫与否，施NO₃^--N处理的生物量和叶片全氮含量都显著高于施NH₄⁺-N的处理，但由于盐胁迫下NO₃^--N降低了Bt蛋白N占全氮的比例（11.0%），叶片Bt蛋白含量则略低于NH₄⁺-N处理。据此认为，盐胁迫下施氮肥通过促进棉株对N素的吸收积累并影响全氮转化为Bt蛋白的比例，进而影响Bt蛋白含量。

Effects of Nitrogen Fertilization on Bt Cotton Growth and Bt Protein Concentration in Leaves under Salinity Stress

It is well known that salinity stress inhibits plant growth and Bt protein synthesis in cotton(Gossypium hirsutum L.),but it is still not clear if fertilization alleviates the inhibitory effects.Two experiments with pot culture and hydroponic culture were conducted using Bt cotton strain K638 in a rain shelter and a greenhouse,respectively,to study the effects of N fertilization and its forms(NO3——N and NH4+-N) on plant growth,nitrogen uptake,Bt protein content and the ratio of N in Bt protein to total N under salinity stress.In the pot experiment,a significant interaction was detected between N fertilization and salinity stress on leaf Bt protein content.Under non-saline and low saline(total salt content≈0.15%) soils,N fertilization enhanced plant biomass by 3.0 and 2.8 times,and increased leaf Bt protein content by 41.0 and 90.9%,and the ratio of N in Bt protein to total N by 9.3% and 15.6%,compared with the non-fertilization treatment,respectively;under moderate saline soil(total soluble salt content≈0.30%),N fertilization also improved plant biomass(1.4 times),total N content(98.8%) and Bt protein level(83.3%),but decreased the ratio of N in Bt protein to total N(7.3%).In the hydroponics experiment,plant biomass and the total N content in NO3——N treatment were higher than that in NH4+-N with or without salinity stress,but the Bt protein levels was slightly lower than that in NH4+-N treatment owing to decreased ratio of N in Bt protein to total N under salinity stress(11.0%).It is concluded that Bt protein concentration in leaves was influenced by nitrogen fertilization under salinity stress through increasing nitrogen uptake and/or altering the ratio of N in Bt protein to total N.