Investigation of yield, phytochemical composition, and photosynthetic pigments in different mint ecotypes under salinity stress.

Salinity stress is one of the main limiting factors of medicinal plant growth and may affect their characteristics and chemical composition. In order to evaluate the response of different species of Iranian mint to salinity stress, an experiment was designed in greenhouse conditions. In this experiment, six Iranian mint species were cultivated in pots under different salinity stress including 0, 2.5, 5, and 7.5 dS/m. The chlorophyll indices (a, b, total, and a/b ratio), carotenoids, total anthocyanin, total phenolic and flavonoid content, antioxidant activity, dry matter yield, and essential oil content were measured in two different harvest stages. Salinity stress affected various measured traits. The results showed that despite the negative effect of salinity stress on photosynthetic pigments, in some ecotypes and species, photosynthetic pigments were not affected by salinity stress. The amount of total phenolic content, total flavonoid content, and total anthocyanin increased in response to salinity stress. The dry matter decreased under salinity stress, but the content of essential oil increased as a result of salinity stress increment. The results of PCA biplot showed that the E16 and E18 ecotypes were separated by a large distance. Among the various ecotypes, E18 had the most desirable traits which can be recognized as a salt-tolerant ecotype. Also, piperita species was the best among the species in all salinity stress levels.

Physiological and biochemical traits in coriander affected by plant growth-promoting rhizobacteria under salt stress.

Salinity is a major environmental stress that limits crop production worldwide. It is well-understood that environmental adaptations, physiological and biochemical traits adjust salinity tolerance in plants, but imparting the knowledge gained towards crop improvement remain arduous. Utilizing the potentially of beneficial microorganisms present in the rhizosphere is an alternative strategy to improve crop production under optimal or stress conditions. The current study aims at examining the ability of plant growth-promoting rhizobacteria (PGPR) in improving coriander growth under salt stress condition. Coriander seeds were inoculated via dual culture of Azospirillum brasiliense and Azotobacter chroococcum, and therefore subjected to four levels of salt stress (0, 40, 80 and 120 mM NaCl) with three replications in a research greenhouse. Seventy-five days after sowing, when leaves fully developed, leaf samples were collected and the traits were measured. The results indicated that the dual inoculation improved chlorophyll a and b content, in comparison to the un-inoculated plants. The dual inoculation increased grain yield, stem fresh and dry weights by 11.6, 11.3 and 17.2%, respectively; it also enhanced total plant fresh and dry weights by 6.1 and 10.2%, respectively, as compared to control. As a result, the dual inoculation significantly improved catalase (CAT), but decreased ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) enzymes activities, as compared to control plants. Salt stress significantly increased (CAT) activity in the leaves, whereas it resulted in significant reduction in (APX) and (GPX) activity, especially in inoculated plants. Furthermore, dual inoculation decreased Na and subsequently increased K concentration in coriander leaves comparing with untreated plants. Overall, these results indicate that the PGPRs has improved coriander growth under control as well as salt stress conditions. Thus, PGPR can could significantly contribute to solve the coriander plant production problems caused by high salinity.

Piriformospora indica confers salinity tolerance on tomato (Lycopersicon esculentum Mill.) through amelioration of nutrient accumulation, K+/Na+ homeostasis and water status.

KEY MESSAGE: Piriformospora indica confers salt tolerance in tomato seedlings by increasing the uptake of nutrients such as N, P and Ca, improving K+/Na+ homoeostasis by regulating the expression of NHXs, SOS1 and CNGC15 genes, maintaining water status by regulating the expression of aquaporins. Piriformospora indica, an endophytic basidiomycete, has been shown to increase the growth and improve the plants tolerance to stressful conditions, especially salinity, by establishing the arbuscular mycorrhiza-like symbiotic relationship in various plant hosts. In the present research, the effect of NaCl treatment (150 mM) and P. indica inoculation on growth, accumulation of nutrients, the transcription level of genes involved in ionic homeostasis (NHXs, SOS1 and CNGC15) and regulating water status (PIP1;2, PIP2;4, TIP1;1 and TIP2;2) in roots and leaves of tomato seedlings were investigated. The P. indica improved the uptake of N, P, Ca and K, and reduced Na accumulation, and had no significant effect on Cl accumulation in roots and leaves. The endophytic fungus also increased in K+/Na+ ratio in roots and leaves of tomato by regulating the expression of NHX isoforms and upregulating SOS1 and CNGC15 expression. Salinity stress increased the transcription of PIP2;4 gene and reduced the transcription of PIP1;2, TIP1;1 and TIP2;2 genes compared to the control treatment. However, P. indica inoculation upregulated the expression of PIP1;2 and PIP2;4 genes versus non-inoculated plants but did not have a significant effect on TIP1;1 and TIP2;2 expression. These results conclude that the positive effects of P. indica on nutrients accumulation, ionic homeostasis and water status lead to the increased salinity tolerance and the improved plant growth under NaCl treatment.

Bio-removal of cadmium from aqueous solutions by filamentous fungi: Trichoderma spp. and Piriformospora indica.

Six strains of Trichoderma spp. and Piriformospora indica have been studied for cadmium tolerance and bioaccumulation capacities by the poisoned food technique. A quantitative assay for Trichoderma spp. and P. indica was conducted in broth cultures supplemented with different cadmium concentrations (0-500 mg/l). In addition, the growth pattern of P. indica was determined by growing the fungus in a solid medium amended with eight concentrations of cadmium (0-200 mg/l). Generally, an increasing cadmium gradient in the culture medium suppressed the ability of fungi for cadmium accumulation. However, a negative relation was observed between the biomass production of fungi and cadmium uptake (q: mg/g biomass). Results showed that Trichoderma spp., especially T. simmonsii [UTFC 10063], are tolerant to cadmium toxicity and have a high ability to cadmium bioaccumulation. The biomass production of T. simmonsii [UTFC 10063] was significantly stimulated and increased by 46.1% when cadmium concentration increased from 0 to 125 mg/l. Moreover, 91.7 and 31.2% of cadmium removal was observed at 10 and 500 mg/l of the cadmium concentration, respectively. P. indica, however, showed a lower tolerance and removal efficiency for cadmium as compared with Trichoderma spp. Therefore, Trichoderma spp., especially T. simmonsii [UTFC 10063], can be exploited as potent bio-removal agents in cadmium-polluted aqueous solutions. Graphical abstract.

Nutritional (Fe, Mn, Ni, and Cr) and growth responses of rice plant affected by perennial application of two bio-solids.

Trace toxic elements often restrict the land application of different bio-solids in agriculture. In order to evaluate the separate influence of the municipal solid waste compost (MSW), sewage sludge (SS) and combined application with inorganic fertilizers (chemical fertilizer (CF)) on nutritional (Fe, Mn, Ni, and Cr) and growth responses of rice plant, a research was conducted on paddy soil from 2013 to 2015. Obtained results showed that SS levels were superior to MSW in most studied traits. The maximum chlorophyll content (46.52), plant height (162.6 cm), biomass (23.33 t ha-1), soil available Fe (206.26 ppm), Ni concentration in the root (14.41 ppm) and shoots (3.16 ppm), Cr concentration in the root (12.43 ppm) and grain (3.65 ppm), and Mn concentration in grain (66.938 ppm) belonged to SS levels, specially enriched 40 t ha-1, when it was added to the soil for three continuous years. The highest 1000-grain weight (29.89 g), yield (6.86 t ha-1), harvest index (48.17%), and soil available Mn (712.7 ppm), Fe, and Ni concentration in grain (107.92 and 8.79 ppm, respectively) were recorded in 3 years of applying the enriched 40 t ha-1 MSW. Accumulation of Ni in grain in critical levels and negative effects of CF treatments on toxic element entry to soil and plant were two important findings of this research that need management.

Essential oil composition of sweet basil (Ocimum basilicum L.) in symbiotic relationship with Piriformospora indica and paclobutrazol application under salt stress.

Essential oil content and oil composition of paclobutrazol treated sweet basil (Ocimum basilicum L.) plant inoculated with Piriformospora indica under salt stress were investigated by GC-MS. The results show a slight increase in essential oil content when basil plants subjected to moderate salinity stress (3 dS m-1 of NaCl). It decreased signifiicantly with increasing salinity level to 9 dS m-1. The findings revealed that leaf area, above ground and leaf dry weights, essential oil content and yield were significantly affected by P. indica inoculation, however paclobutrazol application significantly influenced essential oil yield but not content. Fungal symbiosis as well as paclobutrazol application ameliorated the negative effects of salinity on dry matter and essential oil yield. The main constituents found in the volatile oil of O. basilicum in control treatment were Geranial (26.03%), Neral (24.88%) and Estragole (24.78%). The compounds concentrations showed some differences in P. indica and paclobutrazol treatments. The results demonstrate that micorrhiza-like fungi concomitantly increase essential oil production and biomass in sweet basil, a medicinal herb rich in commercially valuable essential oils.

The critical period of weed control in soybean (Glycine max (L.) Merr.) in north of Iran conditions.

A field study was conducted in 2006 at Sari Agricultural and Natural Resources University, in order to determine the best time for weed control in soybean promising line, 033. Experiment was arranged in randomized complete block design with 4 replications and two series of treatments. In the first series, weeds were kept in place until crop reached V2 (second trifoliolate), V4 (fourth trifoliolate), V6 (sixth trifoliolate), R1 (beginning bloom, first flower), R3 (beginning pod), R5 (beginning seed) and were then removed and the crop kept weed-free for the rest of the season. In the second series, crops were kept weed-free until the above growth stages after which weeds were allowed to grow in the plots for the rest of the season. Whole season weedy and weed-free plots were included in the experiment for yield comparison. The results showed that among studied traits, grain yield, pod numbers per plant and weed biomass were affected significantly by control and interference treatments. The highest number of pods per plant was obtained from plots which kept weed-free for whole season control. Results showed that weed control should be carried out between V2 (26 day after planting) to R1 (63 day after planting) stages of soybean to provide maximum grain yield. Thus, it is possible to optimize the timing of weed control, which can serve to reduce the costs and side effects of intensive chemical weed control.

Study of water stress effects in different growth stages on yield and yield components of different rice (Oryza sativa L.) cultivars.

A field experiment was conducted during 2001-2003 to evaluate the effect of water stress on the yield and yield components of four rice cultivars commonly grown in Mazandaran province, Iran. In northern Iran irrigated lowland rice usually experiences water deficit during the growing season include of land preparation time, planting, tillering stage, flowering and grain filing period. Recently drought affected 20 of 28 provinces in Iran; with the southeastern, central and eastern parts of the country being most severely affected. The local and improved cultivars used were Tarom, Khazar, Fajr and Nemat. The different water stress conditions were water stress during vegetative, flowering and grain filling stages and well watered was the control. Water stress at vegetative stage significantly reduced plant height of all cultivars. Water stress at flowering stage had a greater grain yield reduction than water stress at other times. The reduction of grain yield largely resulted from the reduction in fertile panicle and filled grain percentage. Water deficit during vegetative, flowering and grain filling stages reduced mean grain yield by 21, 50 and 21% on average in comparison to control respectively. The yield advantage of two semidwarf varieties, Fajr and Nemat, were not maintained under drought stress. Total biomass, harvest index, plant height, filled grain, unfilled grain and 1000 grain weight were reduced under water stress in all cultivars. Water stress at vegetative stage effectively reduced total biomass due to decrease of photosynthesis rate and dry matter accumulation.

Effects of Zn rates and application forms on protein and some micronutrients accumulation in common bean (Phaseolus vulgaris L.).

In order to investigation the effects of Zn rates and application forms on protein and element contents (Fe, Cu, Mn, N and Zn) in bean plant, an experiment was conducted as a factorial based on completely randomized design at greenhouse conditions during 2006. Treatments were included zinc rates in 4 levels (10, 20, 30 and 40 mg Zn kg(-1) soil(-1) in ZnSO4 source) and 3 application forms (soil application, seed pelleting and foliar spraying). Results showed that Zn rates had significant effect on accumulation of Zn, Cu, Mn and N in bean leaves. Nitrogen accumulation in leaves reduced with increasing of zinc in the soil. Among Zn application forms, spray application had the highest accumulation of Fe, Zn and Mn in leaves (423.17, 282.89 and 88.17 mg kg(-1), respectively). The highest Zn content in seed was observed in 20 and 40 mg Zn kg(-1) soil(-1) levels (46.39 and 45.62 mg kg(-1), respectively). Meanwhile, all treatments of Zn (both rate and application) had not significant effects on Cu and Mn accumulation in bean seeds. According to interaction effects between Zn rates and application forms, the highest Fe content in seed was observed when 40 mg kg(-1) soil(-1) of Zn was applied as foliar spraying. The seed protein content nearly was stable while Zn levels was increased from 20 to 40 mg Zn kg(-1) soil(-1). Grain yield had significant correlation to zinc and Cu of leaves but, biomass had significant and negative correlation to Zn content of leaves at p < 0.05% probability levels.

Leaf and seed micronutrient accumulation in soybean cultivars in response to integrated organic and chemical fertilizers application.

Plant nutrients can be influenced by organic materials of soils. An experiment was conducted to evaluate the effect of organic amendments on elements uptake by soybean cultivars in a silty loam soil in Mazandaran province, Iran. The experiment was carried out in split plot based on randomized complete block design with three replications in 2006. Main plots were included 8 fertilizer treatments consisted of 20 and 40 Mg ha(-1) Municipal Solid Waste Compost (MSW), Vermicompost (VC) and Sewage Sludge (SS) which enriched with 50% chemical fertilizers needed by soil, only chemical fertilizer treatment and control. Sub plots consisted of three genotypes of soybean (032, 033 and JK). Grain yield was determined and soybean leaves and seeds were digested and analyzed for Mn, Cu, Zn and Fe. Results showed that yield and elements content in soybean leaves and seeds (Mn, Cu, Zn and Fe) were influenced by all treatments. The 40 Mg ha(-1) of sewage sludge enriched with chemical fertilizers produced maximum grain yield. Different soybean cultivars had also significant differences in terms of leaf and seed micronutrients accumulation. Maximum grain yield was observed in JK and 033. Mean comparisons showed that interaction effects of fertilizer and cultivar had significant differences on Mn, Cu and Fe content in soybean leaves, so that the maximum Cu content was observed in 032 cultivars with 40 Mg ha(-1) enriched sewage sludge and municipal waste compost. Also the highest amount of Fe was obtained for JK cultivar when the 40 Mg ha(-1) of municipal compost was used. Among different mentioned traits, Fe and Cu content in leaf and seed and Zn content in leaf had a positive and significant correlation with grain yield.

Investigation the growth, yield and yield components of rice varieties in rotation with garlic, Faba bean, lettuce, pea and fallow in north of Iran.

In order to investigating the effects of second crop cultivation on growth, yield and yield components of rice, a field experiment was conducted at the Rice Research Institute of Iran-Deputy of Mazandaran (Amol) during 2004 and 2005. Tarom as a traditional variety and Fajr as a improved variety were used in this research. Faba, pea, Lettuce and garlic were used as a second crop in rotation with rice. Second crop cultivation, variety and interaction between them had a significant effect on tiller number at 0.01 probability level. Results showed that rice yield after lettuce and garlic rotation was lower than with Faba bean, pea and fallow rotation. These results indicated that rice varieties had different reaction to second crop cultivation. For example, Tarom variety in rotation with lettuce and garlic had higher yield deficiency than Fajr variety. These results suggested that Lettuce and garlic can not be a permanent second crop in paddy field. According to results, pea and faba bean in rotation with rice for the best performance of yield attributes of rice varieties were recommended.

Study the effect of nitrogen fertilizer management on dry matter remobilization of three cultivars of rice (Oryza sativa L.).

In order to study the effect of nitrogen fertilizer management on dry matter remobilization among three rice cultivars, a field experiment was carried out at the Rice Research Institute of Iran-Deputy of Mazandaran (Amol). In 2005, a split-split experiment in the basis of randomized complete block design with 3 replications and 3 factors were used in which fertilizer rate (100, 150 and 200 kg ha(-1) from urea source), fertilizer split application (3 levels in variable ratios in transplanting, tillering and heading stages and cultivars (Tarom, Shafagh and Bahar1) were the treatments. Results showed that nitrogen fertilizer rates and split application had significant effect on dry matter remobilization amount in total shoot, stem and leaves (except flag leaf) in which among cultivars, Shafagh had the highest amount in terms of stem and total shoot dry matter remobilization. This amount was obtained at the 100 kg ha(-1) nitrogen fertilizer and the first split application treatment. The highest rate of dry matter remobilization in leaves (except flag leaf) related to Bahar1 that obtained in 200 kg ha(-1) nitrogen fertilizer level. Also, flag leaf of Bahar1 had the highest dry matter remobilization amount, although was not affected by nitrogen fertilizer rates and split application. Thus, it seams that this part has important role in current photosynthesis at post anthesis stage compared with dry matter remobilization. According to our findings, flag leaf in Tarom cultivar not only has no significant role in dry matter remobilization, but also act as a powerful sink for photosynthetic assimilates.