The interactions between arbuscular mycorrhizal fungi (AMF) and non-host species are poorly studied. Particularly scarce is information on members of the Amaranthaceae/Chenopodiaceae family. Sugar beet (Beta vulgaris) plants were co-cultivated with a host species (Hordeum vulgare) in the presence (+AMF) or absence of Rhizophagus intraradices to explore the hypothesis that the presence of an active, pre-established AMF mycelium induces defense responses in the non-host species. Biomass of sugar beet did not respond to the +AMF treatment, while its root exudation of organic acids and phenolic acids was drastically decreased upon co-cultivation with +AMF barley. The most conspicuous effect was observed on a wide range of potential defense parameters being differentially influenced by the +AMF treatment in this non-host species. Antioxidant defense enzymes were activated and the level of endogenous jasmonic acid was elevated accompanied by nitric oxide accumulation and lignin deposition in the roots after long-term +AMF treatment. In contrast, significant reductions in the levels of endogenous salicylic acid and tissue concentration and exudation of phenolic acids indicated that AM fungus hyphae in the substrate did not induce a hypersensitive-type response in the sugar beet roots and downregulated certain chemical defenses. Our results imply that the fitness of this non-host species is not reduced when grown in the presence of an AMF mycelium because of balanced defense costs. Further studies should address the question of whether or not such modulation of defense pattern influences the pest resistance of sugar beet plants under field conditions.

Effect of Se (as Na 2 SeO 4 at final concentration of 10 µg l -1 ) was studied in two durum wheat (Triticum durum L.) genotypes in perlite under drought conditions. Se treatment increased slightly biomass of both genotypes under drought but not under control conditions. Photosynthetic rate was depressed by drought while increased by Se treatments in both genotypes up to 2.3 fold. However, transpirational water loss was also enhanced in Se-treated plants under both wellwatered and drought conditions. Se application resulted in higher concentrations of soluble proteins and free α-amino acids under drought conditions, but not proline. Our results indicated that Se application improves some physiological parameters such as photosynthesis, accumulation of osmolyes and water use efficiency but did not change significantly plants biomass or water relation parameters. Preučevani so bili učinki Se, dodanega kot Na 2 SeO 4 v koncentraciji 10 µg l -1 na dveh genotipih trde pšenice (Triticum durum L.) gojene v perlitu v razmerah sušnega stresa. Tretiranje s Se je neznatno povečalo biomaso obeh genotipov v razmerah sušnega stresa, a ne pri kontroli. Fotosinteza je upadla s sušo, a se je po tretiranju s Se pri obeh genotipih povečala za 2.3 krat. Transpiracijska izguba vode je bila pospešena pri rastlinah tretiranih s Se v razmerah sušnega stresa kot pri dobro zalitih rastlinah. Uporaba Se se je odrazila v večji koncentraciji topnih beljakovin in prostih α-amino kislin v razmerah suše, vendar ne v koncentraciji prolina. Naši rezultati kažejo, da uporaba Se izboljša nekatere fiziološke parameter kot so fotosinteza, akumulacija osmotikov in učinkovitost izrabe vode, vendar ne spremeni značilno biomase rastlin in parametrov vodnega režima rastline.Ključne besede: organski osmotiki, fotosinteza, prolin, učinkovitost izrabe vode, vodni režim

Effects of selenium (Na 2 SeO 4) was studied in two wheat genotypes under well-watered and drought conditions in greenhouse (15 µg Se L-1) and field (20-60 60 g ha-1) experiments. Application of Se improved dry matter and grain yield under both well-watered and drought conditions. Se increased leaf concentration of pigments and photosynthesis rate under both well-watered and drought conditions. Our results indicated that Se alleviates drought stress via increased photosynthesis rate, protection of leaf photochemical events, accumulation of organic osmolytes and improvement of water use efficiency. Under well-watered condition, Se-mediated growth improvement was associated with higher photosynthesis rate and water use efficiency, greater root length and diameter, and higher leaf water content.

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