Effect of water stress and heavy metals on induction of somatic embryogenesis in wheat leaf base cultures.

In vitro cultures of plant tissues are known to mimic the response of field-grown plants when subjected to stress treatments. This investigation on Triticum aestivum explores the effect of drought stress on somatic embryogenesis and endogenous proline content. Leaf bases were cultured on MS medium supplemented with 2,4-D (10 microM) and different concentrations of PEG (2.5, 5, 7.5%) or mannitol (0.25 and 0.5 M) and also subjected to different periods of aerial drying in the laminar flow for one-day and subsequently transferred to MS basal medium. PEG treatment induced a high percentage (up to 50%) of embryoid formation. However, with mannitol and aerial drying, percentage of embryoid formation decreased with increasing concentrations and duration. After ten days, the endogenous proline content of explants treated with different concentrations of PEG, mannitol and different durations of aerial drying increased with increasing concentration and increasing duration of the treatment, thus, corroborating the role of proline as an osmolyte during stress conditions. Similarly, addition of metals such as cadmium and cobalt caused a reduction in percentage explants depicting embryogenesis. However, when cadmium was employed alone, 22% explants displayed somatic embryogenesis as compared to 54% in 2,4-D treated cultures.