Arbuscular mycorrhizal fungi benefit drought-stressed Salsola laricina

Plant Ecology - Due to its contribution to plant drought tolerance, arbuscular mycorrhizae (AM) may play an important role in the revegetation of degraded pastures in semi-arid and arid regions....     

The effect of thidiazuron level on in vitro regeneration type and peroxidase profile in <Emphasis Type="Italic">Eucalyptus microtheca</Emphasis> F. Muell

The green twigs of 1-year-old Eucalyptus microtheca F. Muell seedlings were cultured on modified MS medium, supplemented with α-naphthalene acetic acid (NAA) and kinetin (Kin) hormones at 12 different concentrations. After 4 weeks, the combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin induced the highest number of axillary shoots. Meanwhile, embryogenic calli were observed in media containing 4 mg l⁻¹ NAA + 0.5 mg l⁻¹ Kin, without any regeneration. The hormone treatments were followed by subculturing the twigs in different levels of thidiazuron (TDZ). The combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin together with 0.01 mg l⁻¹ TDZ resulted in an increase of direct shoot, while higher amounts of TDZ led to adventitious shoot induction. Somatic embryogenesis was observed in the treatment containing 0.01 mg l⁻¹ TDZ + 4 mg l⁻¹ NAA + 0.5 mg l⁻¹Kin. The peroxidase (POD) band patterns in regenerated plantlets were investigated in order to determine the effect of different levels of TDZ on loci synthesis. A dimer locus, a tetramer locus and two epigenetic bands (a new band for NAA + Kin and the other for TDZ) were observed in the POD profiles. In case of low (0.01 mg l⁻¹ and 0.1 mg l⁻¹) levels of TDZ, one heterozygote allele was disappeared from dimer locus, while at higher TDZ levels, the dimer locus lost its stability and tetramer locus showed a high activity. Thus, POD allele patterns seems to be a feasible marker for different types of regeneration.     

Circumscription of taxa in the chasmophilous Iranian Stachys species (Lamiaceae: sect. Fragilicaulis, subsect. Fragiles) inferred from isoenzyme variation patterns

Fresh leaves of 150 individuals from 15 populations representing five putative species of Stachys sect. Fragilicaulis, subsect. Fragiles distributed in the Zagros mountains in western Iran were analyzed for isoenzyme variation. Four enzyme systems (peroxidase, esterase, superoxide dismutase and ascorbate peroxidase) have been studied and a total of 32 bands representing seven putative loci have been analyzed by UPGMA using the Euclidean distances. UPGMA analysis resulted in the recognition of three distinct clusters among the considered populations. The average value of Shannon diversity index (H′) estimated for each population ranged from 0.05 to 2.17. The mean number of bands per isoenzyme ranges from 1.60 to 2.50. The value of Euclidean distance ranges from 0.85 to 3.79. The analysis of isoenzyme variation patterns suggests recognizing following species in Stachys sect. Fragilicaulis subsect. Fragiles: Stachys benthamiana (including Stachys megalodonta), Stachys kurdica (including Stachys ballotiformis) and Stachys asterocalyx. These data also suggest paying more attention to geographical distribution of taxa in Stachys for their taxonomic delimitation. This study provides another strong support for application of electrophoretic analysis of isoenzymes in taxonomy at species level.