Effect of introducing Bacillus thuringiensis gene on nitrogen metabolism in cotton

In the 2001 study, the results indicated that the Bt cotton cultivars (during peak reproductive growth) possessed greater leaf N, free amino acid and soluble protein than their parents. The biggest increase of total nitrogen was at peak boll period, with 36 and 19% increase for Kumian No. 1 and Xingyang 822, respectively. Similar results were found for free amino acid and soluble protein content. Further in 2002, the nitrate reductase activity increased dramatically at peak squaring and early boll open period, the biggest increase at early boll open period, with Kumian No. 1 and Xingyang 822 exhibiting 88 and 61% greater activity than their parents, respectively. The biggest increase in glutamic-pyruvic transaminase activity was at peak boll period, with Kumian No. 1 and Xingyang 822 having 39 and 29% higher activity than their parents, respectively. However, protease activity of Bt cultivars reduced significantly before flowering and early boll open period, the biggest decrease was before the flowering period. The results suggest that the Bt cotton cultivars have a more intense leaf nitrogen metabolism than their parents during reproductive development. The enhanced N metabolism may lead to excessive vegetative growth. Cultural practices should therefore be aimed at reducing leaf nitrogen metabolic strength and keeping the balance of vegetative and reproductive growth.