Influence of water stress on morpho-physiological and phytochemical traits in Thymus daenensis.

Abstract Thymus daenensis is a medicinal plant endemic to semi-arid regions of Iran. A field experiment using a randomized complete block design with four replications was conducted to evaluate the effect of 20, 50 and 80% soil water depletion on morpho-physiological traits, essential oil content and composition and water use efficiency of T. daenensis during 2010-2011. Water stress reduced growth, herbage production, chlorophyll and carotenoid content, while increased proline, K + , essential oil content and irrigation water use efficiency based on essential oil yield (IWUE eso ). Thymol was the highest essential oil composition (63.3-73.5%) followed by carvacrol (3.6-16.0%), ρ-cymene (3.8-7.4%), γ-terpinene (3.3-4.7%), β-caryophyllene (2.8-4.0%) and borneol (1.4-3.4%), respectively. Thymol, ρ-cymene and γ-terpinene were increased, while the other compositions decreased under water stress. It is concluded that irrigation of T. daenensis based on 50% water depletion should be an appropriate choice for first growing season and 80% water depletion for the second growing season in semi-arid climatic conditions

Nitrate and nitrite accumulation in tomato and potato in Ardabil province

The research was conducted to determine the residual nitrite and nitrate on potatoes and tomatoes, two commercially important vegetables in Ardabil province. Samples of these plants were collected randomly from farms and wholesale markets in 10 day intervals at harvesting time in three sites (Ardabil, Parsabad and Meshkin Shahr) during 2004 and 2005. The samples were analyzed for residual nitrate and nitrite using spectroscopic method. The results revealed that in 10% of potato samples nitrate concentration was more than acceptable level (465 – 519.3 mg/kg fresh weight). Nitrite residue in potatoes ranged from 0.1 to 1.12 mg/kg. The nitrite and nitrate concentrations of 83.4% and 33% of tomato samples were lower than detecting limit of the methods. The amount of nitrate in tomato samples of Meshghin shahr was 20 fold lowers than Parsabads region that probably resulted from higher nitrogen fertilizers application in this region

Angular sensitivity of blowfly photoreceptors: intracellular measurements and wave-optical predictions

The angular sensitivity of blowfly photoreceptors was measured in detail at wavelengths λ = 355, 494 and 588 nm. The measured curves often showed numerous sidebands, indicating the importance of diffraction by the facet lens. The shape of the angular sensitivity profile is dependent on wavelength. The main peak of the angular sensitivities at the shorter wavelengths was flattened. This phenomenon as well as the overall shape of the main peak can be quantitatively described by a wave-optical theory using realistic values for the optical parameters of the lens-photoreceptor system. At a constant response level of 6 mV (almost dark adapted), the visual acuity of the peripheral cells R1-6 is at longer wavelengths mainly diffraction limited, while at shorter wavelengths the visual acuity is limited by the waveguide properties of the rhabdomere. Closure of the pupil narrows the angular sensitivity profile at the shorter wavelengths. This effect can be fully described by assuming that the intracellular pupil progressively absorbs light from the higher order modes. In light-adapted cells R1-6 the visual acuity is mainly diffraction limited at all wavelengths.

Metarhodopsin control by arrestin, light-filtering screening pigments, and visual pigment turnover in invertebrate microvillar photoreceptors

The visual pigments of most invertebrate photoreceptors have two thermostable photo-interconvertible states, the ground state rhodopsin and photo-activated metarhodopsin, which triggers the phototransduction cascade until it binds arrestin. The ratio of the two states in photoequilibrium is determined by their absorbance spectra and the effective spectral distribution of illumination. Calculations indicate that metarhodopsin levels in fly photoreceptors are maintained below ~35% in normal diurnal environments, due to the combination of a blue-green rhodopsin, an orange-absorbing metarhodopsin and red transparent screening pigments. Slow metarhodopsin degradation and rhodopsin regeneration processes further subserve visual pigment maintenance. In most insect eyes, where the majority of photoreceptors have green-absorbing rhodopsins and blue-absorbing metarhodopsins, natural illuminants are predicted to create metarhodopsin levels greater than 60% at high intensities. However, fast metarhodopsin decay and rhodopsin regeneration also play an important role in controlling metarhodopsin in green receptors, resulting in a high rhodopsin content at low light intensities and a reduced overall visual pigment content in bright light. A simple model for the visual pigment–arrestin cycle is used to illustrate the dependence of the visual pigment population states on light intensity, arrestin levels and pigment turnover

Evaluation of Morpho-physiological Responses of Iranian Rice Landraces and Improved Genotypes to Iron Deficiency in Nutrient Solution

Excessive application of P fertilizers, use of the bicarbonated water sources for irrigation concomitant to a  low level of organic matter have resulted in widespread iron deficiencies in crop plants in Iran. One of the strategies to overcome this problem is to select tolerant genotypes to iron deficiency (i.e. iron-use-efficient genotypes) or bred genotypes with high-micronutrient-uptake ability. Therefore, this experiment was conducted to study the behavior of twelve Iranian rice landraces and improved genotypes to iron deficiency (Tarom Mahalli, Amol 2, Musa-Tarom, Gharib, Shiroudi, Bejar, Neda, Nogouran, Jozdan, Sazandegi, Zayande Roud, and Kouhrang) as exposed to two levels of chelated iron fertilizers, including 5mM (iron deficiency) and 50mM (no iron deficiency) in Yushida nutrient solution culture.  A factorial experiment based on a completely randomized design with four replicates was carried out in Soilless Culture Center at Isfahan University of Technology, Isfahan, Iran in 2013. The results showed that the iron content, shoot and root dry weights, total dry weight, leaf area, root length and volume and the number of tillers were significantly affected by genotypes, iron fertilizer, and their interaction. The mean dry weights were 0.215, 0.138, and 0.255 g per plant in northern landraces, northern improved, and central Iranian genotypes under no iron deficiency condition, but they were decreased by 25.7, 35.2, and 23.0% under iron deficiency condition, respectively. Based on the magnitude of decrease of total biomass under iron deficiency condition, genotypes such as Musa-Tarom, Bejar, and Zayande Roud seemed to be more tolerant in comparison to Jozdan, Amol 2, and Shiroudi

Effect of Mycorrhizal Inoculation and Pre-treatment with Salicylic Acid at Different Levels of Drought on Morphological Traits and Yield of Flax

The use of plant growth hormones and beneficial microorganisms, could reduce the drought damage. The purpose of this study was to investigate the treatment with salicylic acid and inoculated with mycorrhizal fungi at different levels of irrigation on flax growth. A factorial experiment based on randomized complete blocks design with 3 replications was performed in growth chamber of college of agriculture, Isfahan university of technology and in the years 2010-2011. Treatments were irrigation regimes at 3 levels (100%, 70% and 40% field capacity), mycorrhizae at 3 levels (non-inoculated and inoculated with two species Glomus mosseae and G. intraradices) and salicylic acid in 2 levels (seeds treated with 250 μM concentration of salicylic acid for 8 hours and non-treated seeds). The level of 40% field capacity irrigation reduced the leaf number, root length, root dry weight, height, stem and leaf and total plant dry weight, number and weight of capsules per plant, number of seeds per capsule and seed yield and increased vesicle diameter and percent colonization. Both mycorrhizal species in the three levels of irrigation increased the drought tolerance of the flax but in G. mosseae was more effective. Salicylic acid decreased some of the investigated traits. Inoculation with mycorrhiza and treatment with salicylic acid reduced the investigated characteristics than the inoculation with mycorrhiza and non-application of salicylic acid. 100% field capacity and G. mosseae species were the best irrigation level and mycorrhizal fungi respectively. Therefore it is suggest that application of mycorrhizal fungi especially G. mosseae species increase in the cultivation of flax plants without treatment with salicylic acid, especially in drought conditions because in addition to increased yield, water consumption is also lower and it makes the plant more tolerant to stress conditions such as drought

An Assessment of the Effect of Nitrogen Application and Planting Methods on Yield and Yield Components ofLinseed and Berseem Clover Intercropping System

In order to assess the effect of nitrogen application and planting methods on linseed and berseem clover yield and yield components in an intercropping system an experiment was conducted as a split plot based on randomized complete block design with three replications at the Research Farm of College of Agriculture, Isfahan University of Technology, Isfahan, Iran in 2013. Experimental factors included three levels of nitrogen (zero, 30 and 60 kg ha-1) as main plots and linseed and berseem clover planting methods in 4 levels (pure culture of linseed, berseem clover monoculture, mixed cropping) (50%:50%), intercropping row) 50%:50%)) as sub-plots. Results showed that different levels of nitrogen had no effect on the main stem, seed weight and harvest index of both plants, but the number of lateral branches, number of capsules per plant (linseed), inflorescences number per plant (berseem clover), number of seeds per capsules (linseed), biological yield and grain yield were affected by nitrogen fertilizer. Among the methods of planting, pure cultures of linseed and berseem clover with 1604 and 830 kg ha-1 had the highest yield, respectively. Significant difference between treatments was found in the land equivalent ratio, but the highest land equivalent ratio, was archived at 30 kg nitrogen fertilizer application (1.35) and row intercropping treatment (1.32), respectively. According to the results of this research, the use of berseem clover as a nitrogen-fixing plant, intercropped with linseed under 30 kg of nitrogen application per hectare could, probably, be useful for achieving an appropriate grain yield