The present work describes a procedure that allows for the easy and rapid induction of caulogenesis in four cultivars of Brassica napus L. from transversal Thin Cell Layers (tTCLs). In order to investigate the regeneration ability of this crop, the effects of genotype, explant source and culture medium were examined on shoot regeneration. The tTCL explants were excised from hypocotyl and petiole of 2-week-old seedlings and cultured on a solid basal MS medium supplemented with a-naphthaleneacetic acid (NAA: 0.1-0.4 mg l -1 ), 6-benzylamino-purine (BAP: 1-4 mg l -1 ) and sucrose (20-40 g l -1 ). A significant genotypic effect was observed between the four cvs; Jumbo and Drakkar displayed higher capacities to produce shoots than Pactol and Cossair. Regeneration commenced earlier and the percentage of shoot-producing explants as well as the number of shoots per regenerating explant was greater. The comparison between the regeneration ability of different explants showed that the hypocotyls exhibited a high rate of shoot organogenesis when they were cultured on MS medium supplemented with 3 mg l -1 BAP, 0.3 mg l -1 NAA and 30 g l -1 sucrose. Adventitious shoot buds developed from 46% of the tTCLs, with a mean of 7.5 buds. Furthermore, the method was fast with shoot formation occurring by 7 days culture. Plantlets regenerated from all shoots and developed normally. The regenerated plants were fertile and identical to source plants.

Eliminating heavy metals in the environment by phytoremediation is a method that uses, generally, plants with a low biomass yielded and feeble depth of root system. For the purpose of improving this technique, we have tested four varieties of productive specie with high yields, the rapeseed (Brassica napus L.). In particular, we have studied metal stress effect on biomass, growth, and endogenous Zn and Cd content. Metal treatment caused significant dry weight differences between metal-treated and control plants. A significant genotypic difference has been noticed between the four cv. For two varieties, Jumbo and Drakkar, the accumulation is more important in the stems and petioles, whereas, this accumulation is at a maximum level in the root system for the two varieties, Cossair and Pactol. Chlorophyll and carotenoïd content, as well as lipid peroxidation, known as stress markers, were also evaluated. Metal treatment led to an increase in the amount of malondialdehyde (MDA) in the leaves. However, the increase of Zn and Cd levels in the tissue culture was followed by a decrease in the photosynthetic pigments. To cite this article: A.

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Allelopathic materials inside a tree can produce positive or negative change in the survival, growth, reproduction and behaviour of other organisms if they escape into the environment. To assess these effects, this work was carried out to evaluate the allelopathic impact of Eucalyptus erythrocorys L. on seed germination and seedling growth of two weeds: Sinapis arvensis L. and Phalaris canariensis L.; on one cultivated crop: Triticum durum L. Aqueous; and on ethanolic leaf extracts of E. erythrocorys L. The study was effected using four concentrations (10, 20, 25 and 30 μL/mL) while distilled water was used as a control. The results showed that the E. erythrocorys L. crude extracts had an inhibitory effect on seed germination and seedling growth of both studied weeds and wheat. The inhibition rate was increased by the increase in extract concentration. Only ethanolic extracts of E. erythrocorys L. induced a significant inhibition of seed germination of durum wheat. The effect of E. erythrocorys L. crude extracts was more severe on weeds than on durum wheat. These results indicate that the seedling growth, especially radicle elongation, was the more sensitive indicator to evaluate the effects of extracts than was the seed germination.