Physiological, Biochemical, and Epigenetic Reaction of Maize (Zea mays L.) to Cultivation in Conditions of Varying Soil Salinity and Foliar Application of Silicon.

Soil salinity is one of the basic factors causing physiological, biochemical and epigenetic changes in plants. The negative effects of salt in the soil environment can be reduced by foliar application of silicon (Si). The study showed some positive effects of Si on maize plants (Zea mays L.) grown in various salinity conditions. At high soil salinity (300 and 400 mM NaCl), higher CCI content was demonstrated following the application of 0.2 and 0.3% Si. Chlorophyll fluorescence parameters (PI, FV/F0, Fv/Fm and RC/ABS) were higher after spraying at 0.3 and 0.4% Si, and plant gas exchange (Ci, PN, gs, E) was higher after spraying from 0.1 to 0.4% Si. Soil salinity determined by the level of chlorophyll a and b, and carotenoid pigments caused the accumulation of free proline in plant leaves. To detect changes in DNA methylation under salt stress and in combination with Si treatment of maize plants, the methylation-sensitive amplified polymorphism (MSAP) technique was used. The overall DNA methylation level within the 3'CCGG 5' sequence varied among groups of plants differentially treated. Results obtained indicated alterations of DNA methylation in plants as a response to salt stress, and the effects of NaCl + Si were dose-dependent. These changes may suggest mechanisms for plant adaptation under salt stress.

Micropropagation of Mountain Mulberry (Morus bombycis Koidz.) 'Kenmochi' on Cytokinin-Free Medium.

The aim of the study was to compare two methods of micropropagation of mulberry: single-node culture ("SNC"), and axillary-branching ("AxB"). The experiments were carried out on in vitro cultures for 6 successive passages. The "AxB" cultures were propagated on modified MS medium (+ 25% Ca2+ and Mg2+), supplemented with WPM vitamins, sucrose (30 g L-1), and BA (1.5 mg l-1). The "SNC" cultures were grown on cytokinin-free 1/2 MS (macro- and micronutrients) medium supplemented with WPM vitamins, IBA (0.05 mg l-1), and sucrose (15 g l-1). Both media (pH 5.8) were solidified with agar (7.0 g l-1). Initiation of in vitro cultures from explants taken from adult trees and young, potted plants was feasible on both media. Cultures were established from about 1 cm long nodal explants. Generally "SNC" cultures formed one well rooted, significantly longer axillary shoot with bigger leaves than "AxB" cultures, which developed significantly more shoots and big callus at the explant base. All shoots collected from "SNC" and "AxB" cultures rooted in vivo in peat mixture and developed into similar plantlets. The single-node method based on application of cytokinin-free medium is a good alternative for the axillary-branching method for micropropagation of mountain mulberry (Morus bombycis) "Kenmochi".