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Sackcloth with a softer touch?
Lignin is of course essential for the life of vascular plants and is also very useful to humankind, for example in wood. However, there are situations in which our exploitation of plant material is hindered by lignin. One example of this is in the use of phloem fibres to make fabrics, including the fibres from flax (Linum usitatissimum) and jute (Corchorus sp). Comparing these two, the phloem fibres of flax contain much less lignin than those of jute and hence jute fibres cannot be used to make finer fabrics such as are made from flax fibres. There is thus great interest in identifying varieties of jute with reduced lignin content. Two such lines of Corchorus capsularis have been generated by X-ray-induced mutagenesis, as described by Sengupta and Palit (Kolkata, India, pp. 211-220). They carried out a detailed comparison of one of these lines with wild type jute. Lignin content of the mutant phloem fibres was only about 50 % that of wild type but cellulose content was about 30 % greater. Intriguingly, the tensile strengths of the mutant and wild type fibres were very similar which means that decreased coarseness was not achieved at the expense of strength. However, there were some negative effects: the mutants plants were shorter as a result of lower growth rates and the fibre yield was very much less than in the wild type. In addition to these factors that affect the use of the fibres, the authors also noted that xylem lignification was unaffected in the mutants. The mutation affects specifically the lignification of the phloem fibres and this was attributed to a failure to up-regulate a key enzyme, phenylalanine-ammonia lyase. As the authors point out, these mutants therefore also have great academic interest in that they provide a system for studying positional information in relation to developmental changes in gene expression.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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