Several species from the Brassica genus are very important agricultural crops in different parts of the world and are also known to be heavy metal accumulators. There have been a large number of studies regarding the tolerance, uptake and defense mechanism in several of these species, notably Brassica juncea and B. napus, against the stress induced by heavy metals. Numerous studies have also been published about the capacity of these species to be used for phytoremediation purposes but with mixed results. This review will focus on the latest developments in the study of the uptake capacity, oxidative damage and biochemical and physiological tolerance and defense mechanisms to heavy metal toxicity on six economically important species: B. juncea, B. napus, B. oleracea, B. carinata, B. rapa and B. nigra.

In this study, the effect of different concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn on seed germination and seedling growth at an early stage of two lettuce cultivars (one with green and the other with red leaves) was evaluated. The inhibitory effects of these metals on germination rate, viable seedlings, shoot and root biomass, root length, seedling vigor and root tolerance index was determined. Globally, a decrease was observed in these variables with increasing concentrations of the metals. The present results indicate that seedling growth was more sensitive than germination. Lactuca sativa seeds were usually tolerant for all metals during the germination process and this probably occurred due to barrier effect of seed coat that prevented the metals to come in contact with the developing embryo. The inhibitory effects of these metals on seedling growth varied. In general, the presence of low Ni and Cr concentrations stimulated the growth of greenleaf lettuce seedlings. Low concentrations of Zn promoted the growth of red-leaf lettuce which is less tolerant to Cd. In this study it was verified that Lactuca sativa seedlings can survive in contaminated media, however, it was more sensitive to Cd and Cu and tolerant to Mn.

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Summary In 1997 and 1998, five field studies were conducted at four Portuguese wine‐growing regions in order to evaluate the effectiveness of the chemical control of vineyard weeds under Mediterranean conditions using either reduced doses of residual herbicides or only foliar herbicides. Amitrole (3440 g a.i. ha−1), amitrole + glyphosate mono‐ammonium salt (1720 + 900 g a.i. ha−1), amitrole (3400 g a.i. ha−1), amitrole + diuron (2580 + 1500 g a.i. ha−1), amitrole + simazine (2580 + 1500 g a.i. ha−1), amitrole + terbuthylazine (2580 + 1500 g a.i. ha−1) and amitrole + diuron + simazine (2580 + 1300 + 1400 g a.i. ha−1) were assayed and compared with the following reference herbicides: glyphosate isopropylamine salt (1800 g a.i. ha−1), amitrole + diuron (2520 + 1680 g a.i. ha−1), diuron + glyphosate + terbuthylazine (1275 + 900 + 1425 g a.i. ha−1), amitrole + simazine (1900 + 3900 g a.i. ha−1) and glyphosate + simazine (800 + 2200 g a.i. ha−1). The herbicides were applied during late winter. The results indicated that good control was achieved by the application of foliar herbicides alone or of reduced rates of a mixture of residual herbicides with foliar herbicides for at least 2 months. Three months after application, the efficacy of post‐emergence herbicides and lower rates of residual herbicides decreased significantly in clay soils and under heavy rainfall conditions. Convolvulus arvensis– a weed that is becoming increasingly significant in Portuguese vineyards – was poorly controlled, even when glyphosate was used. Despite this, it can be assumed that in those regions in which the trials were conducted, it is possible to employ weed control strategies that entail the elimination or a reduction in the rate of residual herbicides.