نشریه روابط خاک و گیاه
پیاپی 40 (زمستان 1398)

Salinity is one of the most brutal environmental stresses limiting the productivity of agricultural crops. In order to determine the effect of humic acid on some morphological and physiological characteristics and uptake of elements by strawberry (Fragaria ananassa Duch. cv. Sabrina) under salinity stress, a greenhouse factorial experiment was conducted with three factors including two treatment methods of humic acid application (spray and drench), three humic acid levels (0, 300 and 600 mg/L) and three salinity levels (0, 20 and 40 mM NaCl) in a completely randomized design with four replications. Results revealed that in the salinity level of 40 mM, the dry weights of shoot and root were reduced by 36.65 and 26.85 percents compared to control. With increasing the salinity level, the Na+ concentration increased and the K+, Ca2+ and Mg2+ concentrations in leaves and roots decreased. In the presence of 40 mM NaCl in external media, application of 600 mg/L humic acid increased root Ca2+ concentration by 65 %. However, application of humic acid mitigated the Na+ concentration in leaves and roots and improved the Fe2+ and Zn2+ concentrations. According to the results of this study, application of humic acid (especially at 600 mg/L) ameliorated the deleterious effects of salt stress in strawberry cv. Sabrina

Biochar reduces the bioavailability of a wide range of pollutants, especially heavy metals (HMs).To evaluate the effects of waste biochar of cutflower rose on growth characteristics and accumulation of lead (Pb) and cadmium (Cd) HMs of in lettuce, a factorial experiment, based on completely randomized design, with four replications was conducted. The amount of rose biochar at 3 levels (0, 5 and 10 g/kg), Cd at 3 levels (0, 10 and 20 mg/kg) and Pb at 3 levels (0, 300, 600 mg/kg) were tested. Results showed that the highest amount of leaf area, fresh and dry weight of shoots, and root volume were observed at 5 g/kg level of rose biochar. Increasing the rose-biochar level from 5 to 10 g/kg decreased all traits except height and diameter of shoots. Application of 600 mg/kg Pb decreased the number of leaves, fresh and dry weight of the shoots, fresh and dry weights of roots, and root length by 6.92, 13.38, 18.04, 22.44, 12.66 and 8.61%, respectively, compared to the control treatment. The highest amount of fresh and dry weight of shoots and root volume was observed in 5 g/kg rose biochar and 300 mg/kg Pb treatment, and the least amount of all of the abovementioned traits was observed at the highest levels of biochar and Pb. Increasing the level of biochar from zero to 5 and 10 g/kg and 20 mg/kg of Cd reduced the loss of root Cd by 92.9 and 24.17 percent, respectively. In fact, rose biochar (especially at 5 g/kg level) has improved the lettuce growth characteristics by reducing the bioavailability of Pb and Cd in the soil.

Salicylic acid is an important signal molecule modulating plant responses to abiotic (drought) stresses. A pot factorial experiment based on completely randomized design with three replications was carried out to investigate the effect of salicylic acid on yield and essential oil content of fenugreek under water deficit conditions. Factors were two irrigation levels (50 and 100% of field capacity) and four salicylic acid doses (0, 0.5, 1 and 1.5 mM). Results showed that interaction effect of water stress levels and salicylic acid doses was significant (P≤0.01) for number of pods per plant, 1000-seed weight, protein percent, proline and total soluble sugars. Maximum grain yield (119.2 g/m2) was obtained with application of 1.5 mM salicylic acid and water deficit stress showed significant difference with respect to optimum irrigation. Maximum protein percent (13.83%) was obtained under water deficit conditions and without application of salicylic acid. There was no difference in essential oil percent in 1 mM foliar application of salicylic acid between optimum irrigation (1.4%) and water deficit conditions (1.44%). Therefore, with respect to different responses of studied traits to different levels of salicylic acid, it could be concluded that salicylic acid is able to reduce and adjust the negative effects of water deficit stress on fenugreek plant.

In order to determine the critical period for weed control of greenhouse cucumber, an experiment was conducted in 2012 in a soil greenhouse located 25 km from Mashhad, as a randomized complete blocks design with three replications. The experiment consisted of two treatment series of weed interference. The first series consisted of weed-interference periods (including 14, 28, 42, 56, 70 and 84 days after emergence and the entire growth period of greenhouse cucumber) and the second series consisted of weed-free periods (including 14, 28, 42, 56, 70 and 84 days after emergence and the whole period of greenhouse cucumber growth). Results of this study showed that red root pigweed, common purslane, black nightshade, dwarf mallowand and common lambsquarters were the weeds with the highest density and biomass. Increasing or decreasing the weed-interference and weed-free periods led to changes in density, biomass, relative density and relative biomass of these plants. If 10, 5, and 1% of greenhouse cucumber yield loss are acceptable, then weed control must be carried out from 23 to 77 days (54 days), 18 to 94 days (76 days), and 16 to 107 days (91 days) after the greenhouse cucumber emerges, respectively. In general, the results of this experiment demonstrated that weed control in greenhouse cucumber production is necessary to achieve optimal yield.

Root knot nematode is one of the important plant pathogens that causes damage to many crops, including greenhouse crops. Pepper is an agricultural crop which its cultivation has increased in recent years, especially in greenhouses. Most of the adopted management methods for this nematode have not met the required efficiency. In this study, reaction of some pepper cultivars (Elmina, Tuvana, Chaliston, Sera Demre8, hybrid Aristotle, the California Wonder, Dymaz and Green chilli) to the presence or absence of two root-knot nematodes (M. javanica and M. incognita) was investigated. The nematode was isolated from infested root samples collected from Isfahan and Saveh greenhouses and was identified by the morphometric and morphological characteristics. Nematodes were reared on tomato. The seeds of pepper cultivars were sown in seedling trays and the seedlings with similar growth were transferred to the main pots (having diameter of 15 cm) containing 2 kg of sterilized soil (1:1:1 field soil, sand and manure). At the 4-leaf stage, they were inoculated with 2500 eggs and larvae per kg soil. The experiment was carried out as a factorial based on completely randomized design with four replications. Four months after nematode inoculation, results were evaluated using plants’ growth indices (fresh and dry weight of roots and shoots, length of roots and height of shoots) and growth and developmental factors of nematodes (number of moths per g of root, number of egg colonies per g of roots, number of eggs per colony of eggs, and population of second age larvae per 200 g soil). The Chaliston, California Wonder, hybrid Aristotle and Tuvana cultivars showed low sensitivity to M. javanica nematode, compared to other cultivars. The growth and developmental indices of nematodes in different cultivars showed significant difference. Therefore, based on the Canto-Saenz system, they were divided into two groups of sensitive and resistant cultivars. But all the cultivars were susceptible to M. incognita nematode, except California Wonder cultivar.

An experiment was conducted to select the optimum nutrient solution for growing lettuce (Lactuca sativa L.) under hydroponic conditions (open system) and Shahrekord climate, as a completely randomized design with five different nutrient solutions and three replicates, in Shahrekord University. The nutrient solutions were: 1) Research Station for Floriculture and Greenhouse Vegetables (the Netherlands), 2) Cornel University, 3) Savvas et al., 4) Yamazaki, and 5) Domingues et al. Results showed that maximum shoot fresh weight was obtained by application of Domingues et al. nutrient solution; of course, it had no significant difference with lettuce shoot fresh weight obtained by application of Cornel University and Savvas et al. nutrient solutions. Application of Savvas et al. nutrient solution led to significant increase in shoot Mn, Zn and Cu concentrations in comparison to other nutrient solutions. However, shoot P, K, Ca and Mg concentrations as well as shoot dry weight were not affected by nutrient solutions. Minimum nitrate accumulation in lettuce shoot was observed in plants nourished with Savvas et al. nutrient solution. Based on the maximum shoot fresh weight, minimum nitrate concentration and maximum elements’ concentration in lettuce shoot (Fe, Mn, Zn and Cu), application of Savvas et al. nutrient solution can be recommended for lettuce production in porous substrate hydroponic culture under the conditions of the present study.

In order to study the effect of zinc (Zn) nutrition on relative tolerance of olive (Olea europea L.) seedlings to salinity, a factorial pot experiment was conducted, based on completely randomized design with three replications, during fall 2013. One-year seedlings of two olive cultivars (‘Frontoio’ and ‘Conservolea’) were planted in 10-litre plastic pots containing sand and perlite (1:1 ratio) and treated with nutrient solutions having different levels of sodium chloride (0, 40, 80 and 120 mM) and Zn (0, 1 and 5 µM zinc sulfate). Results showed that salinity reduced root and leaf dry weight, seedling height, number of leaves, potassium/sodium (K/Na) ratio of roots and leaves, and calcium (Ca) molarity ratio in roots and leaves of both cultivars. With increasing Zn content to 5 µM, all the growth traits of the two cultivars were increased significantly. This trend was observed in the leaf K content and K/Na ratio of roots and leaves as well. Interaction of Zn×cultivar and salinity×cultivar was significant only on root dry weight. The Frontoio cultivar had maximum root dry weight at all salinity levels. The Zn had a positive and significant effect on root and leaf dry weight. Interactions of Zn×salinity and Zn×cultivar were not significant on leaf dry weight. Frontoio cultivar was more tolerant cultivar to salinity according to the maximum root and leaf dry weight, as well as other studied traits. Application of Zn not only raised growth indices, but also increased K absorption, K/Na ratio, and Ca molarity ratio. This role led to improved nutrition conditions and finally increased dry leaf and root weights. In general, Ca molarity ratio is more proper index in comparison with K/Na ratio to determine tolerance to salinity in the olive seedlings