Danijela Djunisijevic-Bojovic

Lead uptake increases drought tolerance of wild type and transgenic poplar (Populus tremula x P. alba) overexpressing gsh 1

Growth and development of plants largely depends on their adaptation ability in a changing climate. This is particularly true on heavy metal contaminated soils, but the interaction of heavy metal stress and climate on plant performance has not been intensively investigated. The aim of the present study was to elucidate if transgenic poplars (Populus tremula x P. alba) with enhanced glutathione content possess an enhanced tolerance to drought and lead (Pb) exposure (single and in combination) and if they are good candidates for phytoremediation of Pb contaminated soil. Lead exposure reduced growth and biomass accumulation only in above-ground tissue of wild type poplar, although most of lead accumulated in the roots. Drought caused a decline of the water content rather than reduced biomass production, while Pb counteracted this decline in the combined exposure. Apparently, metals such as Pb possess a protective function against drought, because they interact with abscisic acid dependent stomatal closure. Lead exposure decreased while drought increased glutathione content in leaves of both plant types. Lead accumulation was higher in the roots of transgenic plants, presumably as a result of chelation by glutathione. Water deprivation enhanced Pb accumulation in the roots, but Pb was subject to leakage out of the roots after re-watering. Transgenic plants showed better adaptation under mild drought plus Pb exposure partially due to improved glutathione synthesis. However, the transgenic plants cannot be considered as a good candidate for phytoremediation of Pb, due to its small translocation to the shoots and its leakage out of the roots upon re-watering.

Micropropagation of Achillea millefolium L. on half-strength MS medium and direct rooting and acclimatization of microshoots in hydroponic culture.

The aim of this study was to determine the possibility of micropropagation of the medicinal plant A. millefolium on half-strength MS medium and ex vitro rooting and acclimatization of the obtained microshoots in hydroculture in order to establish an efficient production method. Two explant types were used: basal and terminal cuttings, and better results were achieved when terminal cuttings were used. The development of shoots in the multiplication phase was successful with a regeneration percentage of 100%. Ex vitro rooting in a modified Hoagland nutrient solution was successful (83%), but the percentage of in vitro rooting on half-strength MS medium without hormones was higher (95%). However, bearing in mind that mass production of A. millefolium is more efficient when the phase of in vitro rooting is excluded, this method could be recommended for commercial propagation of this medicinal plant. It is necessary to conduct additional research in order to optimize the composition, EC and pH value of the hydroponic nutrient solution. [Projekat Ministarstva nauke Republike Srbije, br. 43007]

Quick-dip and contact method of cutting rooting of Zelkova carpinifolia (Pall.) K. Koch as an alternative non-invasive species

Two methods of rooting of Zelkova softwood cuttings were analyzed: (1) quick-dip method and (2) contact method - the thin polyethylene film (20 mm) laid directly over the cuttings during the rooting process. The control for contact method was a low tunnel with a thick polyethylene film. One group of cuttings in the contact method was treated with quick-dip (IBA 2,500 μg•mL-1, carrier-ethyl alcohol) during 5 sec, and the other group was treated with water solution of IBA (50 μg•mL-1) in 24-hour treatment. The third group was control - untreated cuttings. The same groups of cuttings were also used in low tunnels. The number and length of primary and secondary roots were measured on rooted cuttings. The results of all treatments show that contact method in combination with water solution of IBA was the best with 92% of rooted cuttings. No significant differences were obtained between this treatment and quick-dip + contact method (85.3%). Rooting of cuttings under low tunnel was significantly lower. In general, contact method was better than low tunnel, disregarding the carrier used. These results recommend the almost unknown contact method in nursery propagation of Zelkova, as an alternative, non-invasive species for the conditions in Serbia.