NATURAL REGENERATION UNDER FOREST PLANTATIONS: "GREEN DESERTS" OR MILIEU FOR BIODIVERSITY?

Although commercial forest plantations have been termed "green deserts", several studies from the last two decades have reported the opposite. These studies suggest that forest plantations can catalyze the natural regeneration in their understory and, thus, contribute to biodiversity conservation. In order to obtain a wide and multi-faceted panorama of forest plantations and their potential contribution to biodiversity conservation and forest restoration, previous studies investigating natural regeneration under forest plantations have been reviewed, highlighting those carried out in Brazil. Methods and environmental conditions are quite variable among studies, making generalizations difficult. Nevertheless, results indicate that historical and environmental factors, such as canopy density and light availability, plantation age, forest species, distance from natural forests, silvicultural practices, and previous land use directly or indirectly affect natural regeneration richness, abundance and community structure under forest plantations. The reviewed studies, as a whole, reinforce the idea that commercial forest plantations can act as environments of biodiversity, at least for some life forms, and, in addition, can facilitate the restoration of native forests. Although the Brazilian studies are abundant, they have been restricted to a few regions and biomes and are mostly descriptive studies. Experimental studies focusing on specific factors that affect the natural regeneration dynamic under forest plantations as well as on management techniques in order to combine high production and biodiversity conservation are desirable. Nonetheless, other biomes and regions rather than those already studied, where forest plantation is a common land use, should be considered.20353355

Cytotoxic effect of the diterpene lactone dehydrocrotonin from Croton cajucara on human promyelocytic leukemia cells

Diterpenes exhibit potent antineoplastic properties against human and murine carcinoma cell lines. trans-Dehydrocrotonin from Croton cajucara, a Brazilian medicinal plant, is a nor-diterpene with antiulcerogenic activity. In this work, we examined the effect of trans-dehydrocrotonin (t-DCTN) on the vitality of HL60 cells by assessing the MTT reduction, protein content and phosphatase activity of these cells. Protein quantification indicated that t-DCTN reduced the number of cells with an IC50 of 500 muM; mitochondrial function (MTT reduction), was also inhibited (IC50 = 300 MM), when the cells were treated for 24 h. In contrast, when the cells were treated with this lactone in the initial plating and cultured for 96 h, t-DCTN was more toxic for all parameters analyzed: MTT and phosphatase activity (IC50 = 180 muM) and protein content (IC50 = 150 muM). The flavonoid utilized as positive control myricetin and the following IC50 values were obtained after 24 h of treatment: 300 and 192 muM for protein content and MTT reduction, respectively. According to the chemical characteristics of both compounds, the cytotoxic effect of t-DCTN could be explained through two mechanisms: adduct formation with DNA and proteins and/or oxidative stress induction.691676