Hairy roots of Brassica napus (rape cv. Giant) were produced by cocultivating leaf and cotyledon explants with Agrobacterium rhizogenes strain A4T. The hairy roots grew prolifically on solid and in liquid media. Incorporation of ammonium sulphate or phosphinothricin (PPT) into the media reduced growth. PPT treatment reduced glutamine synthetase (GS) activity and increased the ammonia content of the hairy roots. We have found that PPT treatment also induces a loss of glutamine from the roots and this may influence root growth. To test this we grew hairy roots in a liquid medium containing 10 mM glutamine. This glutamine treatment overcame the PPT induced suppression of growth but also significantly increased GS activity, reduced ammonia accumulation and increased the levels of glutamate and asparagine.
Shoots were regenerated from 12-mm diameter leaf discs derived from greenhouse plants of Limonium perigrinum (Bergius), with either zeatin or thidiazuron (TDZ), the latter producing five times the number of shoots. After 8 weeks exposure to a modified Murashige and Skoog basal medium (BM) supplemented with 3.0 mg/litre TDZ, an average of 13 shoots/disc formed, 90% of which were 1 mm long. There was no significant difference in the total number of shoots formed at 1.0-5.0 mg/litre TDZ, however at lower rates (1.0-2.0 mg/litre) a greater proportion of longer shoots (> 1 mm) developed. Shoots regenerated after 8 weeks from leaf discs exposed to BM with TDZ for from 2 h to 6 weeks before being transferred to growth-regulator-free medium. A mean of 4.8 shoots/disc formed from the shortest TDZ pulse period, with the majority being longer than 1 mm. Serial sections of discs pulsed with TDZ medium showed many suppressed shoot initials within the new tissue originating from the cut edge of the discs.
H93056
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