Journal of Soil and Plant Interactions

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Gerbera (Gerbera jamesonii L.) is one of the most important cut flowers in the world and nutrient solutions are the most important elements that increase quality and quantity of gerbera flowers. In this study, the effect of adding silicon, as an important mineral, from two sources of potassium silicate and nano silica, was investigated on physiological traits of gerbera flower, cv. Yanara. In this experiment, various concentrations of potassium silicate and nano silica were applied in different treatments including spray of nano silica in two concentrations of 12.5 and 25 mg/L (based on SiO2), drench of nano silica in two concentrations of 12.5 and 25 mg/L (based on SiO2), drench of potassium silicate in two concentrations of 25 and 50 mg/L (based on SiO2) and control (with no treatment), in three replications. The results showed that nano silica in both forms and concentrations decreased fresh weight of the flowers, but increased under-stomatal carbon dioxide. Number of flowers was increased under the 25 mg/L nano silica treatment, compared to control. Although there was no significant difference between treatments in dry weight of flowers and all photosynthetic parameters such as transpiration, photosynthesis, water use efficiency, and stomatal conductance, but in general, nano silica increased number of gerbera flowers while, potassium silicate could not improve the studied traits.

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One of the main factors of an aggregate hydroponic system is to use a suitable plant media with local origin. Thus the objective of this research was to study the possibility of replacement of cocopeat as an imported material with local materials and the effects of such media on the growth and flowering characteristics of Rosa hybrida cv. Maroussia. A randomized complete blocks design experiment with four replications was conducted. The treatments were nine growing media: cocopeat (100%), perlite (100%), leca (100%), cocopeat (75%) + zeolite (25%), perlite (75%) + zeolite (25%), leca (75%) + zeolite (25%), cocopeat (50%) + perlite (50%), cocopeat (50%) + leca (50%) and perlite (50%) + leca (50%). Results indicated that plants grown in cocopeat and cocopeat + zeolite showed high vegetative and reproductive growth. The highest number of flowers per plant was observed in in cocopeat (8.31) and cocopeat + perlite (7.81) substrates, which had no significant difference with cocopeat + zeolite medium (6.87). Adding zeolite to cocopeat, perlite and leca improved length of flower bud and number of flowers per plant over their pure medium. Also, adding cocopeat to perlite increased fresh and dry weight of cut flowers and number of flowers per plant. Based on the results and availability of zeolite in Iran, mixture of cocopeat (75%) + zeolite (25%) is recommended.

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Production of many cut flowers, such as lilium, is very common in Iran. Flower quality has special importance in lilium flower production process, and proper nutrition is one of the major effective factors. This research was conducted to investigate the effect of different concentrations of potassium silicate, nano-silicon and calcium chloride on concentration of potassium, calcium and magnesium, chlorophyll index and number of florets of Asiatic lily 'Brunello'. The experiment was carried out based on randomized complete blocks design with 9 treatments and 3 replications (each replication included 5 pots), in Educational/Research Greenhouses of Isfahan University of Technology, Isfahan, Iran. Treatments included drench of potassium silicate at three concentrations (25, 50 and 75 mg/L), spraying of 25 mg/L potassium silicate, spraying of calcium chloride at two concentrations (25 and 50 mg/L), spraying of nano-silicon at two concentrations (12.5 and 25 mg/L) and control (no treatment). Number of florets, chlorophyll index and concentrations of calcium, magnesium and potassium in stem and leaves were measured. Results showed significant differences between treatments in stem and leaf calcium and magnesium, leaf potassium, chlorophyll index at harvest time and number of florets. Drench of 25 mg/L potassium silicate had maximum number of florets per plant (5.27) and stem magnesium. Spraying 50 mg/L calcium chloride showed maximum leaf calcium, magnesium and potassium, respectively, with 4.38, 15.75 and 16.43 percent increase as compared to control. Spraying of 25 mg/L calcium chloride, with 38.9 percent increase as compared to control, had maximum stem calcium. Maximum chlorophyll index at harvesting time was related to spraying 25 mg/L potassium silicate. In general, if the goal is production of more florets, then drench of 25 mg/L potassium silicate is an appropriate treatment.

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A greenhouse experiment, as hydroponic, was carried out in order to investigate the response of sunflower genotypes (Hison125, Iroflor and Bliezer) to different levels of salinity (0, 60 and 120 mM of NaCl) and Fe (0, 50 and 100 mM) in nutrient solution. The experiment was arranged as factorial, based on a completely randomized blocks design with four replications. Results showed that plant height, leaf area, shoot and root dry weight, ratio of shoot/root dry weight, K concentration, the ratio of K/Na concentration in shoot and roots were reduced and the concentration of Na was increased as the level of salinity was increased in the nutrient solution. There was a significant increase in the values of plant height, leaf area, shoot dry weight and the ratio of shoot/root dry weight as the level of Fe in the nutrient solution was enhanced from 5 to 50 mM. However, with a further increase from 50 to 100 mM, there appeared no significant changes in the amount of these traits. The interaction between genotype and Fe level was significant on the root dry weight and K concentration in the leaves. The lowest and the highest increase in root dry weight, in response to increased level of Fe, was observed in Hison125 and Bliezer cultivars, respectively. However, the difference between cultivars became less in treatments containing higher levels of Fe in the nutrient solution. Considering the K concentration in leaves, only Bliezer cultivar showed positive response to increasing Fe level. The interaction between salinity, genotype and Fe level was significant on the concentration of Fe in plant. Based on the results, increasing Fe concentration in the nutrient solution improves sunflower growth. However, the increased concentration of Fe could not significantly alleviate the negative effects of salinity.

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Petroleum hydrocarbons (PHs) are one of the most important soil contaminants. Presence of these compounds in soil may cause some stresses to plants and make the growth conditions unfavorable. Thus, for landscaping in the contaminated areas, tolerant plants to these stresses are needed. The aim of this research was to determine morphophysiological characteristics of two native and non-native bermudagrass species in a soil with 0, 2.1, 3.87 and 12.25 percent by weight PHs:soil. A factorial experiment, based on randomized complete blocks design with three replications, was performed in research greenhouse of College of Agriculture, Isfahan University of Technology, Isfahan, Iran. Results showed that application of 2.1% PHs to soil significantly reduced color and density of bermudagrasses (3.3% and 5%, respectively), and the growth of native and non-native species was reduced by 31.1% and 7.3%, respectively. Relative water content and chlorophyll content were significantly decreased and proline content was increased, when soil pollutant content by PHs was increased. Also, the increase in contaminants content up to 2.1% increased catalase activity. But, higher rates of contamination reduced its activity, as compared to control. Conclusively, both bermudagrass species had acceptable turf quality and therefore could be recommended to be used in PHs-polluted soils although quality and growth of non-native bermudagrass was better than the native one.

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Sophora japonica is a deciduous tree with fragrant white flowers and panicle inflorescence. This tree has not been used widely in the landscape of central. One of the reasons is lack of enough information about asexual propagation of this plant. In the present experiment, effects of different concentrations of indole butyric acid (IBA) and indole butyric acid-potassium salt (K-IBA) (0, 5000, 10000, 15000 and 20000 mg/L) was evaluated on hardwood cuttings of Sophora  japonica with/without bottom heat. Results showed that no root formation occurred in the hardwood cuttings without bottom heat, while callus was produced. Bottom heat significantly affected all measured traits. The highest rooting percentage was obtained by 20000 mg/L IBA and K-IBA (56.66% and 53.33%, respectively), 80 days after planting the cuttings. The highest root length at 80^th day after planting was obtained with 20000 mg/L K-IBA. Rooting percentage, number of roots, leaf area, roots carbohydrate content of roots and fresh and dry weights of roots, stem and leaves increased with increasing the hormones level. However, with decreasing hormones concentration, the ratio of sprout buds to dormant buds and the amount of carbohydrates in leaves were increased.

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Abstract
Drought is one of the most important abiotic stresses limiting the survival, growth, and production of plants in many regions of the world including Iran. Genetically, different species adopt different strategies to confront with drought. One of the mechanisms that plants have evolved to adapt to the environmental changes is stress memory. In this study, different genotypes of smooth bromegrass were evaluated to investigate the drought stress memory and drought stress tolerance based on a greenhouse pot experiment. Thirty three genotypes of smooth bromegrass were evaluated in three moisture environments: control (C), once drought-stressed (D2), and twice drought-stressed (D1D2) in a factorial arrangement according to the randomized complete blocks design with two replications. The dry matter yield decreased by 45 and 36% in the one-stress and two-stress treatments compared to the control, respectively. These results indicated the role of drought stress memory in modulating drought stress through the influence on forage dry yield and root dry weight. The root dry weight reduced in the once stress and twice stress conditions by 32 and 19%, respectively, compared to the control environment. This finding shows the significant effect of stress memory on the root growth. Based on the principal component analysis, superior genotypes were identified for future researches. Overall, the results suggested that smooth bromegrass is capable to activate some drought stress memory mechanisms related to morphological and root traits.

Background and Objective: Smooth bromegrass is particularly adapted to areas with medium and low annual precipitations and has a high drought tolerance when compared with the other grasses. Drought is one of the most important environmental factors with adverse effects on plant growth and development and affects all morphological, physiological, biochemical and metabolic aspects of plants (Farooq et al., 2009). Therefore, it is necessary to identify drought-tolerant genotypes (Saeidnia et al., 2017b). The term stress memory was first proposed by Trewavas (2003), as the plant's ability to access past experiences to better respond to future stresses. In open-pollinated species that are difficult to develop inbred lines, such as smooth bromegrass, the main breeding method is to create synthetic varieties that are obtained through the crossing of suitable parents. Besides, half-sib matting is one of the most common methods for obtaining genetic information such as estimating the additive effects and dominance of genes (Nguyen and Sleper, 1983). Saidnia et al. (2017a) in a study on the genotypes of orchardgrass species found superior genotypes for hay production. They also examined the genetic parameters and heritability of dry matter yield and introduced the superior genotypes for the further researches. Hence, this study was designed to investigate stress memory and its effect on improving drought tolerance in a smooth bromegrass germplasm.

Methods: This research was carried out from February 2017 to June 2018 in the research greenhouse located at the Isfahan University of Technology as a pot experiment. A sandy loam soil with bulk density, field capacity, and wilting point of 1.57 g cm^-3, and 12.5 and 7.4 %w/w, respectively, was used for filling the pots. The genetic materials included 33 genotypes of smooth bromegrass that were collected from different regions of the country and some foreign gene banks. The genotypes were investigated in three moisture environments including control (C), once drought-stressed (D2) and twice drought-stressed (D1D2) as a factorial experiment in the form of a randomized complete blocks design with two replications.

Results: The analysis of variance showed that drought treatments had a significant effect on most of the traits. A significant difference was observed between the genotypes regarding the measured traits indicating high genetic diversity among the genotypes. The secondary drought stress significantly reduced most of the traits. The dry matter yield decreased by 45 and 36% in the once-stress and twice-stress treatments compared to the control, respectively. These results indicated the role of drought stress memory through the effect on dry yield of forage and root dry weight. Also, the root dry weight was reduced by 32 and 19% in the conditions of one stress and two stress compared to the control environment, respectively, which shows the significant effect of stress memory on the root system. Multivariate analysis showed that under the twice stress condition compared to the other two moisture environments, the relationships of the traits have undergone severe changes, which is a confirmation of the effect of initial stress and stress memory.

Conclusions: This research indicated a high genetic diversity among the smooth bromegrass genotypes in terms of stress memory responses, which can be used in the selection methods. For example, the means of dry matter yield and root dry weight decreased to a lesser extent when grown in the presence of twice drought stress, than once drought stress. This finding shows that the mechanisms of the stress memory related to morphological and root traits in this plant are activated by applying preliminary mild drought stress and help the plant to have a smaller decrease in growth. Based on the principal component analysis, superior genotypes were identified for future research. The results of this research can be used in breeding programs and future genetic research. It is also suggested that suitable genotypes be studied more in field conditions over several years.

References:
1. Farooq, M., Wahid, A., Kobayashi, N., Fujita, D., Basra, S.M.A., 2009. Plant drought stress: effects, mechanisms and management. In: Alberola, C., Debaeke, P., Lichtfouse, E., Navarrete, M., Véronique, S. (Eds.), Sustainable Agriculture. Springer Dordrecht. pp. 153–188.
2. Nguyen, H.T., Sleper, D.A., 1983. Theory and application of half-sib matting in forage grass breeding. Theor. Appl. Genet. 64, 187–96.
3. Saeidnia, F., Majidi, M.M., Mirlohi, A., 2017a. Genetic analysis of stability in poly­crossed populations of orchardgrass. Crop Sci. 57, 2828–2836.
4. Saeidnia, F., Majidi, M.M., Mirlohi, A., Manafi, M., 2017b. Productivity, persistence and traits related to drought tolerance in Smooth Bromegrass. Plant Breeding. 136, 270–278.
5. Trewavas, A., 2003. Aspects of plant intelligence. Ann. Bot. London. 92, 1–20.