Isolation of transgenic cells and embryogenesis

Resistant crop plant (without foreign gene)

Resistant transgenic crop plant

Due to its similarity with glutamic acid, phos-phinotricin ("Basta") inhibits glutamine synthetase. It is inactivated by N-acetylation.

Strategies for the creation of Basta-resistant crops

In principle, there are two strategies to introduce Basta resistance into a plant:

1. Increasing the expression of the plant's own gene that the herbicide targets, i.e. the gene for glutamine synthetase. Thus plants remain undamaged or only slightly damaged at Basta concentrations that kill wildtype plants (strategy I).

2. Introduction of a Basta-inactivating foreign gene, i.e. the gene for N-acetyltransferase from Streptomyces (strategy II).

In the first case a non-transgenic plant is produced, whereas in the second the plant is transgenic.

3.5.1 and Fig. 2.3.7 F) has been mainly attributed to such atmospheric pollutants.

In the past, trees in the areas of smelting works and power stations fuelled by lignite were damaged lethally by the high S02 concentrations (e.g. in the Erzgebirge of Germany). Current regulations on air pollution have resulted in a decrease in the concentrations of these pollutant below the threshold of damage (Fig. 1.9.5). However, this raises the question: "What is the damaging concentration?" In principle, the impact of stress depends on the product of time and concentration of a noxious substance; however, in practice, this applies only conditionally. For almost all gaseous pollutants exists a range of concentration (below the so-called threshold) where the pollutant does no damage, and may even be useful. Not everything emitted from the exhaust of a motor vehicle is, from the perspective of the plant, a damaging gaseous pollutant - C02 and nitric oxides, and to a certain extent even S02, can contribute to the mineral nutrition of plants. In making such a general statement, the different sensitivities of the individual plant species must be considered (Table 1.9.3), which in turn depend on the developmental stage of the plant.

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