Induction and characterization of oil palm (Elaeis guineensis Jacq.) pro-embryogenic masses.
Oil palm is one of the most economically valuable oil seed plants, but the expansion of plantations has been limited by availability of seedlings, as the conventional propagation is through seeds, which have low germination rates. One possible solution for the large-scale production is the use of somatic embryogenesis. The aim of this study was evaluate the effects auxins 2,4-D and picloram on the induction of pro-embryogenic masses in E.guineenesis hybrid leaf explants and characterize, regarding embryogenic characteristics, with cytochemical and ultrastructural analysis. Specifically, in vitro plantlets leaves fragments were inoculated in Y3 culture medium supplemented by 2.4-D or picloram at different concentrations (0.0, 1.0, 3.0, 6.0 and 9.0 mg l⁻¹). After 90 days the presence/ absence of cell masses were evaluated. Both growth regulators efficiently induced cellular masses regardless of the concentrations applied. As the cell masses were not homogeneously formed, they were classified according to color and shape into four types: TYPE 1--elongated and translucent, TYPE 2--uneven and translucent, TYPE 3--globular and beige, TYPE 4--globular and white. Based on the anatomical and ultrastructural features, TYPE 2, 3 and 4 cell masses were considered to have the highest embryogenic potential and therefore may be most suited to large-scale vegetative propagation of oil palm.
Cell Viability, Mitotic Index and Callus Morphology of Byrsonima verbascifolia (Malpighiaceae)
The combined analysis of cell viability, mitotic index and callus morphology of species of commercial interest may favor the identification of cell masses with embryogenic characteristics at early stages of cultivation, allowing the development or improvement of protocols for in vitro plant regeneration through indirect embryogenesis. Byrsonima verbascifolia L. (DC.) (Malpighiaceae) is a Brazilian medicinal species native to the Cerrado, which has a low seed germination rate due to tegument dormancy. This study aimed to identify cells with embryogenic characteristics during growth of callus of B. verbascifolia, by assessing cell viability, mitotic index and cell morphology. Callus was induced from leaf explants and inoculated on MS medium with 4.52 μM 2,4-D and 4.44 μM benzylaminopurine (BAP). Friable calli were obtained at four distinct growth phases: lag (until the 30th), exponential (from 31st to the 70th day), linear (from 71st to the 100th day) and decline (from 101st to the 120th day). Calli with 20 and 30 days showed cells with embryogenic characteristics, that is, isodiametric shape, juxtaposed, with small vacuoles, thin cell wall and presence of amyloplasts. After 120 days, calli were mostly elongated cells with lower cell viability and mitotic index.
LAND DEGRADATION IN THE DEVELOPING WORLD: ISSUES AND POLICY OPTIONS FOR 2020
Land degradation takes a number of forms, including depletion of soil nutrients, salinization, agrochemical pollution, soil erosion, vegetative degradation as a result of overgrazing, and the cutting of forests for farmland. All of these types of degradation cause a decline in the productive capacity of the land, reducing potential yields. Farmers may need to use more inputs such as fertilizer or manure in order to maintain yields, or they may temporarily or permanently abandon some plots. Degradation may also induce farmers to convert land to lower-value uses. For example, farmers may plant cassava, which demands few nutrients, instead of maize, or convert cropland to grazing land.