| Cotton is characterized by high requirement for and low utilization capability of potassium. However, resource of potassium is very poor in china and fertilizer K has been applied much lower than fertilizer N and P for long time. Consequently grown in most soils cotton appears severe deficiency of potassium. Transgenic technology advances the study on potassium transporter genes of plant. Introducing of potassium transporter gene into cotton is believed to be one of the efficient measures for improvement of potassium nutrition which can also promote the study of potassium transportation in cotton. Indeed transgenic technology greatly contributes to improvement of cotton growth such as Bacillus thuringiensis (Bt) transgenic cotton, which has been widely grown in the world since 1996 due to their resistance to insects where Bt proteins play an important role. However, the introduction of Bt gene also affects vegetative and reproductive growth of cotton. It is reported recently that Bt cotton is more sensitive to potassium deficiency than it's parent cotton, which can enhance the crisis of potassium deficiency of cotton field in china and should be fully noticed with the rapid development of Bt cotton production.There were two transgenic cotton cultivars used in this study. One was Bt transgenic cotton (sukang103) which had been planted widely, the other was KAT1 transgenic cottons which included two experimental lines (C1&C2). Their parent cotton is sumian12. Indirect and direct effects of foreign gene on plant potassium nutrition were analyzed in order to improve potassium transport research and afford bases of fertilization for produce of insect-resistant (Bt) cotton.Hydroponic experiments were carried out to study potassium transport rates in cotton sap with supply of different potassium concentrations, kinetic parameters in potassium uptake in the existence of competitive cations NH4+ and Na+, and distribution of potassium in seedlings both in Bt transgenic cotton (Sukang103) and it's parent (Sumian12). The results showed that at three-leaf stage Bt cottons had lower K content in root, highermaximum potassium uptake rate (Vmax) of root and faster upward-transportation of potassium from root to shoot than the non-Bt transgenic (parent) cottons.Induced changes of the uptake, transport and allocation of potassium and sodium, SOD activity and H2O2 content in leaves of Bt (Bacillus thuringiensis) transgenic cotton(Sukangl03) by different level of salt stresses were compared with its parent (Sumianl2) at the early growth stage . The results showed that, in comparison to non-transgenic cotton seedlings exposed to salt stress, selection of Bt cotton seedlings for potassium was weakened during the transport from root to shoot in the Bt transgenic cotton, consequently more sodium was accumulated in the shoot and resistibility against salt stress was dropped than that in the control. Furthermore, SOD (superoxide dismutases) activity in leaves of the Bt cotton decreased significantly in salt stress, which might reduce the ability of eliminating superoxide radicals(O2-).Our results suggest that Bt cotton is more sensitive to salt stress than regular cotton and may not be suitable to be planted in saline soils.Growth properties of both regular cotton and transgenic cotton with over expressing potassium channel gene were continuous recorded throughout whole growth period in pot. Uptake and utilization of mineral potassium by cotton were studied under sand condition as well as potassium efflux and uptake kinetics under hydroponic conditions. The results showed that introducing of potassium channel gene accelerated early vegetative growth of cotton, slowed reproductive growth and raised branch node position of the first bud. Furthermore, both of potassium channel transgenic lines had lower rate of potassium efflux in roots and higher uptake capability of potassium at low external potassium concentration (0.1mmolL-1) than that of parent cotton. Both lines of Cl and C2 accumulated more potassium in shoot than t... |
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