BOTANY Higher Secondary Second Year - Textbooks Online

y a number of firms. Plants have been engineered to produce human
proteins, such as hormones, in their seeds. A weed called mouse-eared
cress has been engineered to produce a biodegradable plastic
(polyhydroxybutyrate, or PHB) in tissue granules.
Transgenic dicotyledonous plants
1. Nicotiana tabacum 4. Helianthus annuus
2. Beta vulgaris 5. Solanum tuberosum
3. Glycine max 6. Gossypium hirsutum
Transgenic monocotyledonous plants
1. Asparagus sp. 3. Zea mays
2. Oryza sativa 4. Avena sativa
Herbicide resistance in transgenic plants
Under normal circumstances, herbicides affect photosynthesis or
biosynthesis of essential amino acids. Under field conditions, application
of herbicides not only kills the unwanted weeds but also greatly affects
the field crops. In order to protect the crops against exposure to herbicides,
scientists after intensive research isolated a gene from Streptomyces
hygroscopicus which encodes an enzyme, capable of inactivating the
herbicide ‘Basta’. Transgenic plants with this gene have been developed,
demonstrating effectiveness of this gene for protection against herbicide
‘Basta’. Thus, herbicide-tolerant crop plants have now been developed
by genetically manipulating plant genomes resistant to specific herbicides.
Improved resistance to insect pests and microbial diseases
Genes from Bacillus thuringiensis (Bt 2 ) have been introduced into
several crops, including tomato and cotton, and field-testing has
demonstrated impressive results against many pests. Spore preparation
of this bacterium is used as a biological insecticide during the last 20
years. Insecticidal activity depends on a toxic protein called delta
endotoxins. The toxin gene (Bt 2 ) from Bacillus thuringiensis has been
isolated and used for Agrobacterium. Ti plasmid mediated transformation
of tobacco, cotton and tomato plants. The transgenic plants were resistant to the
Manducta sexta, a pest of tobacco. India had acquired technology from U.S.A. for
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