The objective of this study was to investigate the effect of exogenous selenium (Se) supply (0, 2, 4, 8, 16 μM) on the growth, lipid peroxidation and antioxidative enzyme activity of 100 mM NaCl-stressed melon (<em>Cucumis melo</em> L.) seedlings. Salt stress significantly reduced the growth attributes including stem length, stem diameter, dry weight and increased antioxidative enzyme activity [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT)]. Moreover, the plant exhibited a significant increase in electrolyte leakage and malondialdehyde (MDA) content under NaCl stress. Se supplementation not only improved the growth parameters but also successfully ameliorated the adverse effect caused by salt stress in melon seedlings. However, the mitigation of NaCl-stressed seedlings was different depending on the Se concentration. At lower concentrations (2–8 μM), Se improved growth and acted as antioxidant by inhibiting lipid peroxidation and increasing in SOD and POD enzymes activity under salt stress. At higher concentrations (16 μM), Se exerted diminished beneficial effects on growth. Whereas CAT activity was enhanced. The result indicated that Se supplementation had a positive physiological effect on the growth and development of salt-stressed melon seedlings.

Posttranscriptional control of gene expression can be achieved through RNA interference when the activities of Dicer-like (DCL), argonaute (AGO) and RNA-dependent RNA polymerase (RDR) proteins are significant. In this study, we analysed the expression of seven AGO, five DCL and eight RDR genes in cucumber under cold, heat, hormone, salinity and dehydration treatments using quantitative reverse-transcription PCR (qRT-PCR). All CsAGO, CsDCL and CsRDR genes were differentially expressed under abiotic stress treatment. In response to abiotic stress treatment, most genes were expressed at higher levels in flowers or stems than in other organs, whereas some CsAGOs (CsAGO1c, CsAGO6 and CsAGO7) and CsRDRs (CsRDR1d and CsRDR2) were highly expressed in roots during dehydration treatment. The expression patterns indicate that most CsDCLs, CsAGOs and CsRDRs respond to abiotic stress, and stems or flowers are the most sensitive organs, followed by roots. This is the first report of expression analysis of all CsDCL, CsAGO and CsRDR family genes in cucumber under abiotic stress, which provides basic information and insights into the putative roles of these genes in abiotic stress. The results of this study should serve as a basis for further functional characterization of these gene families in cucumber and related Cucurbitaceae species.

To understand how sulfur nutrition affects the quality and yield of vegetable plants, we have grown two cultivars of pakchoi (Brassica campestris L. ssp. chinensis var. communis cv. Shang Hai Qing and You Dong Er) hydroponically in nutrient solution supplied with two levels of sulfur (0.0558 mM as sulfur deficiency and 1.0058 mM as sulfur sufficiency, respectively) for three weeks and their growth, nutrient uptake and glucosinolate content under these two sulfur conditions were investigated. The results showed that plant growth of both the cultivars was inhibited by sulfur deficiency. The concentrations of nitrogen and magnesium in shoots of both the cultivars were increased notably under sulfur deficiency, but there was no significant change in concentrations of sulfur, potassium and calcium. Moreover, sulfur deficiency increased phosphorus uptake in You Dong Er but not in Shang Hai Qing. In Shang Hai Qing sulfur deficiency reduced the content of all individual and total glucosinolates, while in You Dong Er this was also the case for most individual and total glucosinolates. However, in You Dong Er the total aliphatic glucosinolate concentration was not significantly influenced but the concentrations of individual aliphatic glucosinolates-glucoalyssin and gluconapin were in contrast increased under sulfur deficiency. Our data show that sulfur deficiency will decrease the yield and deteriorate the quality of pakchoi vegetable by reducing its growth and the contents of nutrients and glucosinolates. In addition, there was a significant genotypic variation in the composition and content of glucosinolates between these two pakchoi cultivars when exposed to sulfur deficiency.Additional key words: aliphatic glucosinolate, genotype, nitrogen, plant growth, sulfur sufficiency Hort.