Iranian Journal of Plant Physiology
Volume:9 Issue: 1, Autumn 2018

Cadmium is a main toxic pollutant and poses a considerable threat to human health. In other to study the effect of Cd stress on traits of garden cress and radish, an experiment was conducted based on a completely randomized design in an aeroponic system. In this study CdCl2 was used at three levels (control, 3, and 6 mgl-1). Seeds were cultivated in an aeroponic system and Hoagland nutrient solutions (with and without Cd) were used for irrigation. Morphological traits and cadmium accumulation were measured after 40 days. Results for garden cress showed the highest plant height (32.67 cm), leaf number (30.83), root length (14.5 cm), dry weights of roots (0.34 g) and shoots (1.52 g), fresh weights of roots (2.27 g) and shoots (11.3 g) in the control and the 6 mg l-1 cadmium chloride resulted in the highest cadmium accumulation in roots and shoots 2.88 and 0.11 kg/g, respectively. Also in radish the results showed the highest plant height (50.1 cm), leaf number (18.8), root length (26.7 cm), dry weights of roots (0.41 g) and shoots (2.04 g), fresh weights of roots (3.9 g) and shoots (27.01 g) in the control and the 6 mg l-1 cadmium chloride produced the highest cadmium accumulation in roots and shoots 3.3 and 0.28 kg/g, respectively. Findings showed that proline, total phenol, and anthocyanin contents increased under cadmium stress in garden cress and radish.

In recent years, the use of soil microbial potential including arbuscular mycorrhizal fungi is widely considered to enhance the better growth and nutrition of plants. This research was conducted in order to study the impact of mycorrhizal fungi on the increase of yarrow production and the plant establishment affected by the symbiotic relationships between fungi and yarrow plant, based on factorial experiment as a randomized complete block (RCB) design with 4 treatments. Inoculated treatments included non-inoculated condition as control mode, inoculated with G. fasciculatum, G. mosseae and G. intraradice fungi. At the end of growth season, some growth parameters such as colonization, plant establishment, essential oil percentage and also morphological properties including fresh and dry weight of shoot and root and the root volume were measured. Results showed that the inoculation of Achillea millefolium L. with arbuscular mycorrhizal fungi have a significant effect on the measured parameters. This means that the inoculation with mycorrhizal fungi leads to increasing the plant establishment and essential oil percentage, fresh and dry weight of shoots and roots, and also the root volume compared to the control mode. It is noteworthy that among the three treatments done with fungi, the treatment of G. fasciculatum showed the most increase in the above parameters.

Valeriana officinalis (valerian), as a nutraceutical herb, is widely used for its sedative and hypnotic properties. It is known that C15 sesquiterpenoid valerenic acid (VA) is the active ingredient responsible for pharmacological effects of V. officinalis. To evaluate the effect of methyl jasmonate (MeJA) concentrations (50 and 100 µM) in the modulation of expression patterns of the genes involved in valerenic acid (VA) biosynthesis, transcript abundance of identified sesquiterpene synthase (Sesqui-TPS) genes in the root of V. officinalis was monitored by quantitative real time PCR (qRT-PCR) within a 144 h time period. In addition, Valerenic acid contents were measured by high-performance liquid chromatography (HPLC). The highest amount of VA (12.45 mg/g dry weight (DW)) was found at 100 µM MeJA with a 12 fold increase over control culture (1.03 mg/g DW) at exposure time of 72 h. Moreover, MeJA in a concentration dependent manner enhanced transcription rate of VoTPS1 and VoTPS7 genes. Accordingly, exposure to 100 µM MeJA for 24 h can be more effective in the induction of these genes than that observed for 50 µM. Such enhancement was correlated with increased VA accumulation suggesting that these genes may be responsible for the biosynthesis of intermediates involved in the VA-biosynthetic pathway. However, MeJA treatment seemed to have a less significant effect on VoTPS3 expression than VoTPS1 and VoTPS7 genes. This results provide insights for more effective biosynthesis of VA by MeJA-mediated transcriptional changes of putative sesqui-TPS.

The aim of this study was to analyze the effect of drought stress on the kinetics of leaf elongation in relationship to the variation of sugar concentrations and their net deposition rates along the elongation zone of leaf 4 of durum wheat plants. Plants were grown in soil in a naturally illuminated greenhouse, and water was withheld from seedlings for a period of 14 days. Leaf 4 of 26 day-old plants was used for growth measurements and tissue sampling. Relative elemental growth rates (REGR), cell displacement velocity (DV), and elongation zone length (EZL) were significantly reduced by drought treatment. Together, this resulted in a decrease in leaf elongation rate (LER) in drought-stressed plants. Epidermal cell length along the elongation zone was not significantly affected by drought stress, indicating that the decrease in elongation zone length was due mainly to a reduction in cell production rate. The concentration of total soluble sugars (TSS) and non-reducing sugars (NRS) was highest at the leaf base and decreased distally from 10 mm from the leaf base in plants grown under non-stressed (control) conditions. Drought stress caused a significant accumulation of TSS at the leaf base, mainly through an increase in non-reducing sugars. The continuity equation was used to calculate sugar net deposition rates. Drought stress increased the net deposition rates of non-reducing sugars in the first 10 mm from the leaf base. This increase was the principal source for the increase in non-reducing sugars concentrations at the leaf base in response to drought.

In order to investigate chitosan and magnesium-nano fertilizers’ impact on photosynthetic pigments, protein, proline, and soluble sugar contents of sesame under irrigation cut-off treatment, a split-factorial experiment was conducted based on randomized blocks with three replications. Irrigation cut-off based on BBCH scale as the main factor (normal irrigation and irrigation cut-off in 6 and 75 BBCH stages). Secondary factors as subplot included Oltan and Dashtestan-2 sesame cultivars, and foliar application of Mg-nano fertilizer (application and non-application) and chitosan (control, foliar application of 4.8 g.l-1 in 65 BBCH and 6.4 g.l-1 in 75 BBCH stages). Based on the results, severe drought stress (irrigation up to 65 BBCH) resulted in reducing the mean of chlorophyll a, b, and total compared to the control treatment. Chitosan foliar application yielded more desirable results compared to those of Mg-nano fertilizer and caused an increase in the mean traits of chlorophyll a, b, total, carotenoid, protein, proline, and soluble sugar. In addition, irrigation up to 65 BBCH (severe drought stress) and non-application of nanofertilizer led to a decrease in chlorophyll content and physiological damage. Based on the findings, chitosan biopolymer, as a natural substance, as well as co-application of these two can be an appropriate action in order to decrease the plant damage under drought stress regarding the role of Mg in chlorophyll structure and a large number of the plant vital enzymes.

Arsenic (As) is a toxic metalloid which is usually found in rice fields as a contamination and has negative effects on the plant growth and reduces the crop yield. Similar to heavy metals, the deleterious effects of As may be due to, at least in part, the amount of absorbed As and disturbance of the plant water status. In this connection, different varieties of the same species may show differential performances. Comparative responses to 75 µM AsIII were evaluated in two Iranian rice cultivars adapted to moderate-humid vs. very warm and dry climates (Hashemi and Amber, respectively). Although both cultivars absorbed AsIII, but its translocation factor was lower in Amber accompanied by accumulation of soluble sugars and glycine betaine and lower level of internal ABA. Moreover, adverse effect of AsIII onrelative water content and stomata closure was less prominent in Amber, compared to Hashemi. Results suggest that cultivars adapted to dry conditions are more capable to withstand against As and to control its entrance to human food chain.

Growers often apply high amounts of chemical fertilizers for vegetable production and this application contributes to concerns about nitrate levels in food. An experiment was conducted to investigate soil N amendment effects for reducing the nitrate accumulation and improving the quality of fresh purslane (Portulaca oleracea L.). Treatments included four levels of animal manure as follows, N-based broiler litter (T1), P-based broiler litter (T2), N-based cattle manure (T3), P-based cattle manure + urea (T4), four levels of chemical fertilizer equivalent to organic treatments, and a T0 (no fertilizer and manure). Results showed that nitrate levels of broiler litter and cattle manure treatments were significantly lower than those of chemical fertilizer treatments. The highest level of nitrate in the first harvest was recorded in the T7 treatment and higher levels were recorded in T5 and T7 treatments in the second harvest. In the first harvest, T1 and T2 treatments had higher appearance quality but in the second harvest, appearance quality of T2 and T5 treatments showed a significant increase compared to the other treatments. It is concluded that organic manure application results in higher quality as compared with the inorganic fertilizer andreduces nitrate accumulation in fresh purslane.

Triticum aestivum L. and Zea maize L. are both sensitive to salinity stress which is a major problem faced by farmers today. In the present study, the effect of chitosan, a biologic elicitor under salinity stress was examined on growth parameters and biochemical markers in maize and wheat seedlings. Seeds of wheat and maize plants were coated with chitosan 25%, 50%, and 75% solutions before they were planted and subjected to 0, 50, 100, 150, and 200 mM salinity stress under a 11/8 h photoperiod and at 25±2 °C temperature condition during 7 days. Then, the growth parameters including germination percentage, root and shoot growth as well as seedling weight were recorded. The biochemical markers including catalase and peroxidase activity and malondialdehyde, proline, and protein contents were measured at day seven of the experiment. Significant difference in relation with growth parameters was observed at high concentrations of chitosan in comparison with the control plants under salt stress. Catalase and peroxidase activity and protein content increased under salinity stress and chitosan at high concentration reduced catalase and peroxidase activity. Salinity stress induced lipid peroxidation and malondialdehyde accumulation while chitosan reduced malondialdehyde content of the plants under salinity stress. The synthesis of protein was significantly increased with increasing the chitosan concentration. Generally, the growth parameters of both seedlings were improved and unfavorable effects of salinity were reduced when the seeds were coated with chitosan. Application of chitosan at low concentrations increased antioxidant enzyme activity and proline content and decreased MDA accumulation. In conclusion, chitosan at an appropriate dose improved growth performance and biochemical marker fluctuation under salinity stress.