Journal of Soil and Plant Interactions

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Aloe vera is a perennial liliaceous plant with succulent green leaves joined at the stem in a whorled pattern. It is highly appreciated due to its short growth period and high economic value among all the aloe species, and is used in pharmaceuticals, cosmetic products and food products. In order to improve Aloe vera cultivation in soilless culture, an experiment was conducted in 2011 in greenhouse of College of Agriculture, University of Guilan, Rasht, Iran, as a split plot bi-factorial in completely randomized design with four replications. Four nutrient solutions containing different levels of nitrate and potassium were the main plot, which were sampled at six different periods. Results revealed that the nutrient solutions affect measured traits after 5-6 months. In other words, in research programs for this plant, it is better to record the data for at least 5-6 months. In general, the nutrient solution containing 9.8 mM nitrate and 5.8 mM potassium lead to the best results in all sampling periods. In fact, Aloe vera plants respond positively to high levels of nutrients and in solutions containing the highest level of nitrate and potassium show the highest amount of measured traits.

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Lack of sufficient water resources and drought stress is one of the main problems for crop production in arid and semi-arid regions of the world, such as Iran. The use of water absorbing polymers (hydrogels) improves water retention capacity of soils and can lead to optimal use of the restricted water resources. In this research, the effects of four levels of Aquasorb water-absorbing polymer (0, 2, 4, and 8 grams Aquasorb per kg of soil) and three irrigation frequencies (3, 6 and 9 day intervals) on growth indices, yield and water use efficiency (WUE) of greenhouse cucumber, cultivar Negar, were investigated. The results showed that yield and growth indices of the cucumber were affected by the application of hydrogel and increased as compared with control. Also, water consumption by cucumber decreased significantly as the irrigation interval increased. The highest yield (196.3 g/plant) was obtained when the hydrogel was used at the rate of 2 g/kg of soil and irrigation interval was 6 days. Although the use of hydrogel increased water consumption of the cucumber, but its application at the rate of 2 g/kg soil significantly increased WUE (17.0 g/L) of this plant.

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Abstract
Phosphorus deficiency and drought stress are limiting factors in wheat yield. Drought stress has different effects on the uptake, utilization and use efficiency of soil phosphorus in wheat cultivars. The purpose of this study is to investigate the response of growth and development, uptake and efficiency of phosphorus in Sirvan and Sivand wheat cultivars at three moisture stress levels of 50, 70 and 95% of soil field capacity (FC) and two phosphorus levels of 0 and 25 mg kg^-1. The results showed that addition of phosphorus increased shoot dry weight, phosphorus utilization efficiency, root length and area, and soluble sugars by 42, 61, 84, 47, and 66%, respectively, and decreased electrolyte leakage by 64% under stress conditions of 50%FC. Besides, the phosphorus application of 25 mg kg^-1 under drought stress conditions of 50%FC increased the shoot dry weight of the Sirvan variety by 75% compared to the Sivand variety. This increase can be due to the effect of phosphorus on metabolic activities inside the plant, which has led to an increase in root growth, soluble sugar production and cell wall resistance, and a decrease in electrolyte leakage. Therefore, the positive changes observed in different traits and indices due to the use of phosphorus increased the resistance of the Sirvan cultivar compared to Sivand under drought stress conditions. According to the results of phosphorus efficiency and some root morphological and physiobiochemical characteristics, Sirvan cultivar showed a good response to phosphorus fertilizer in modulating the effect of drought stress.

Background and Objective: Drought is one of the most widespread abiotic stresses which has a negative effect on the growth and yield of plants in most areas of the world. Drought stress reduces plant yield by decreasing the uptake of water and nutrients. The arid and semi-arid climate conditions of Iran have caused many problems in the production of plants, including wheat (Triticum aesivum L.). Phosphorus, as one of the essential nutritional elements for plants, can be effective in alleviating drought stress (Kang et al., 2014). In recent years, the use of plants and cultivars efficient in uptake nutrients, including phosphorus, as an appropriate strategy to increase crop yield in water-limited environments has been the focus of researchers. Phosphorous efficient cultivars are important due to their special physiological and morphological characteristics in drought stress conditions (Neji et al., 2019). Therefore, it is necessary to pay attention to the mechanism of efficient cultivars against drought stress for accurate fertilizer recommendations.

Methods: To evaluate Sirvan and Sivand wheat cultivars, in phosphorus uptake and efficiency and growth and development at different levels of moisture stress and phosphorus, a factorial experiment was performed based on a completely randomized design with three factors and three replications during the vegetative growth period in the greenhouse. The factors included phosphorus from Ca(H₂PO₄)₂·H₂O (0, and 25 mg P kg soil^-1), three moisture regimes including 50, 70 and 95% of field capacity (FC) and two spring wheat varieties (Triticum aesivum L.) of Sivand as a drought-sensitive variety and Sirvan as a drought-resistant variety.

Results: According to the results, it was observed that the application of phosphorus (25 mg kg^-1) was effective on the growth and development of the studied wheat cultivars under non-stress and drought stress conditions. Application of phosphorus increased shoot dry weight, phosphorus utilization efficiency, root length and area, and soluble sugars by 42, 61, 84, 47, and 66%, respectively, and decreased electrolyte leakage by 64% under drought stress conditions of 50%FC. Also, the phosphorus application of 25 mg kg^-1 under drought stress conditions of 50%FC increased the shoot dry weight of Sirvan variety by 75% compared to Sivand variety. This finding can be due to higher root growth and its characteristics (root area and cumulative length), uptake and utilization of soil phosphorus and physiobiochemical characteristics in Sirvan variety. The application of phosphorus with a positive effect on the growth and development of the Sirvan variety in the vegetative growth stage made it adapt to drought stress conditions.

Conclusions: The application of phosphorus at the level of 25 mg kg^-1 under drought stress conditions increased the shoot dry weight, root area and length, phosphorus uptake and efficiency, and soluble sugars and decreased electrolyte leakage. These changes were more noticeable in Sirvan variety. The use efficiency of phosphorus in the stages of vegetative growth can play an important role in determining the resistance of cultivars to drought stress. It is considered a good feature for a suitable fertilizer recommendation in order to improve the yield of agricultural products. Also, using the appropriate level of phosphorus can play an effective role in the efficiency of drought-resistant cultivars.

References:
1. Kang, L.y., Yue, S.C., Li, S.Q., 2014. Effects of phosphorus application in different soil layers on root growth, yield, and water-use efficiency of winter wheat grown under semi-arid conditions. J. Integr. Agric. 13(9), 2028–2039. https://doi.org/10.1016/S2095-3119(14)60751-6.
2. Neji, M., Kouas, S., Gandour, M., Aydi, S., Abdelly, C., 2019. Genetic variability of morpho-physiological response to phosphorus deficiency in Tunisian populations of Brachypodium hybridum. Plant Physiol. Biochem. 143, 246–256. https://doi.org/10.1016/j.plaphy.2019.09.006.