نشریه روابط خاک و گیاه
پیاپی 50 (تابستان 1401)

Association of the plant with microorganisms such as dark septate endophytic fungi reduces the harmful effects of environmental stresses such as salinity. In this experiment, the effect of dark septate endophytes isolated from date palm roots on increasing salinity resistance of tomato (Lycopersicon esculentum cv. Super cheif) was investigated. The experiment was performed as a factorial in a completely randomized design with two factors including the type of isolate at 13 levels [4-B, 8-B, 10-D, 11-C, 14-A, 15-D, 16-A, 19-F, 21-A, 22-C, 22-E, 39-D, control (PDA plug)], and salinity at 3 levels (zero, 50 and 100 mM sodium chloride) with 3 replications. Tomato plants were inoculated with fungal isolates separated from date palm roots under salinity. Based on ANOVA results, in symbiosis with fungal isolates of 4-B and 11-C, the negative effects of salinity (up to 100 mM and equivalent to 9.52 dS/m) on tomato biomass were reduced. At salinity of 100 mM, 4-B had the highest plant fresh weight and 11-C had the highest plant dry weight compared to other treatments and were 55.51 and 26.55% higher than the non-inoculated treatments, respectively. By increasing the salinity level up to 100 mM, isolates of 4-B, 8-D, 10-D and 11-C had high efficiency in decreasing sodium concentration, increasing potassium concentration and potassium to sodium ratio. Symbiosis with some fungi (10-D and 8-B) caused a significant increase in phosphorus concentration (19%) compared to non-inoculated plants. At different salinity levels, isolates of 11-C, 39-D and 10-D increased the leaf relative water content. Increase in salinity up to 50 mM (equivalent to 5.44 dS/m) was associated with increased endophytic dependency and isolates of 11-C and 4-B showed the highest increase (43%) compared to other isolates.

A pot experiment in soilless culture was performed as a factorial experiment based on the randomized block complete design with four replications in the research greenhouse of Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. The effect of foliar application of methyl jasmonate (MeJA) [distilled water (control), ethanol 1% (as solvent of MeJA and control), 1 and 2 mM MeJA] and Zn application (0, 0.025, 0.05 and 0.1 mgL-1) in Hoagland nutrient solution on the growth characteristics, photosynthetic pigments, and essential oil production of Mentha piperita L. was evaluated. According to the results, the highest growth was observed in 0.025 mg L-1 Zn and foliar application of 1 and 2 mM MeJA. The highest photosynthetic pigments of chlorophyll a and total chlorophyll were obtained in 0.025 mg L-1 Zn and foliar application of 2 mM MeJA. The highest root fresh and dry weights, chlorophyll b and carotenoid were observed in 0.05 mg L-1 Zn and foliar application of 2 mM MeJA and the treatment without Zn and foliar application with distilled water. In addition, the highest amount of essential oil production was observed in 0.1 mg L-1 Zn and foliar application with 1 mM MeJA. In general, 0.025 mg L-1 Zn and foliar application of 2 mM MeJA was the best treatment and improved most studied traits. The results of this experiment showed that Zn in low concentrations stimulate the peppermint growth; whereas Zn omission or application of high concentrations created some stressful effects in this plant increasing its essential oil production. Therefore, application of proper concentrations of Zn and MeJA can be a suitable way to improve the growth and essential oil production of peppermint.

Plant nutrition management and soil fertility are among factors that determine crop productivity and sustainability under agro-ecosystems conditions. A pot experiment was conducted to investigate the effect of vermicompost provided from sugarcane bagasse and foliar application of microalgae extract of Spirulina on growth parameters, grain yield and yield attributes of rapeseed. The experiment was a factorial combination of Spirulina extract and bagasse vermicompost arranged in a complete randomized block design with four replications. Plants were foliar sprayed with three different concentrations of Spirulina extract (i.e., 0, 2, 4, and 6 %v/v) and application of five vermicompost mixtures based on mass percentage of bagasse and buffalo manure (i.e., 0%, 75% bagasse + 25% buffalo manure, 50% bagasse + 50% buffalo manure, 25% bagasse + 75% buffalo manure, and 100% buffalo manure). Spirulina extract and vermicompost interaction effects on the length of root, root weight, leaf area, chlorophyll pigments, 1000-seed weight, protein and oil content in seed, grain yield and harvest index were significant. The highest seed oil content (43.35%) and seed protein content (36.85%) were recorded in plants foliarly sprayed with 6% Spirulina extract. Application of vermicompost resulting from a mixture of buffalo manure + bagasse with the higher ratio of buffalo manure to bagasse gave better seed and oil yield as compared to other vermicompost treatments.

Nutrient solutions used in the production of lettuce in soilless culture do not contain silicon (Si) as a beneficial element. Therefore, this experiment aimed to evaluate the role of Si in lettuce growing hydroponically. Results showed that the highest fresh weight, dry weight and total dry weight of lettuce were obtained in the control. The highest percentage of the edible part to root was observed in 0.5 mM silicon treatment. In the shelf life aspect, the lowest percentage of lettuce weight loss was recorded in 0.5 and 1.25 mM silicon concentrations and the best food quality was obtained in the treatment of 0.75 mM silicon. The highest stomatal conductance and transpiration rate were observed at the Si concentration of 0.25 mM and the highest antioxidant activity was observed at a concentration of 0.5 mM. The highest phenol and flavonoids were recorded in the treatments of 1.75 and 2 mM silicon, respectively. The highest leaf silicon concentration was found in the treatment of 1.75 mM silicon and the lowest amount of nitrate in lettuce was obtained in the concentrations of 0.25 and 0.5 mM silicon.

Under water stress conditions, growth-promoting rhizobacteria could alter root characteristics, leading to increased plants yield. A controlled experiment with two barley cultivars, Dasht, and Kavir, was carried out with four inoculations of Bacillus simplex strains (31-2, 42-3, 51-4, and control), in two irrigation levels of 80 and 50% of field capacity. The results showed that inoculation with the mentioned bacteria increased the biological yield of barley by 28% under water stress condition compared to the control treatment. The effect of bacteria was cultivar dependent. B. simplex 31-2 had the most significant effect on the biological yield of Kavir cultivar, and B. simplex 42-3 on the Dasht cultivar. Linear relationships between root characteristics and barley's biological yield were observed. The highest coefficients of determination (R2) were obtained with fresh root weight (84%), root volume (83%), and root surface (81%). Considering the relationship between root traits and the biological yield of barley and the role of B. simplex 31-2 in a 121% increase in root area under water stress, it seems that this trait is the essential mediator of yield. Due to the insignificance effect of B. simplex 3-32 on the root characteristics, against the increase of shoot performance by this bacterium, its mode of action may be due to inducing improvement on other physiological pathways. Overall Bacillus bacteria are effective in mitigating the negative effect of water stress on barley and these bacteria can be considered effective candidates for the production of biofertilizers.

Root exudates and morphological root traits play an important role in plant species’ response to drought. However, the functional consequences of these drought-induced changes for rhizosphere microbial communities are unknown. We hypothesized that drought-sensitive and -tolerant grass genotypes widely differ in the quality of root exudates, growth strategies, and root systems, which may affect rhizosphere microbial communities. Therefore, we examined microbial biomass carbon and nitrogen in the rhizosphere of drought-sensitive and -tolerant genotypes of Bromus inermis, Dactylis glomerata, and Festuca arundinacea species under four years water stress treatments at Lavark Farm of the Isfahan University of Technology. Responses of the rhizosphere microbial communities to the water stress varied by the plant genotypes. Water stress increased rhizosphere microbial biomass carbon in the drought-sensitive and -tolerant genotypes of Bromus inermis species. In contrast, water stress treatment significantly reduced microbial biomass in the rhizosphere of Dactylis glomerata genotypes. The effect of water stress on rhizosphere microbial biomass carbon was positive in the drought-sensitive genotypes of Festuca arundinacea species, while conversely, this effect was negative in the drought-tolerant genotypes. We found a similar pattern across two drought-sensitive and -tolerant genotypes of Bromus inermis species to the water stress, which could be an evolutionary strategy to overcome drought conditions through the stimulation of microbial biomass and activity and the subsequent mineralization of nutrients. Higher microbial biomass carbon in the rhizosphere soils relative to those in the control (bulk soil) were observed, regardless of the moisture treatment. Under the water stress, microbial biomass carbon were almost simillar in the rhizosphere of drought-sensitive and -tolerant genotypes but were higher in the drought-tolerant genotypes without the stress.