The Efficiency of Mycorrhizal Fungi on Growth Characteristics and some Nutrients Uptake of Plane tree Seedling (Platanus orientalis L.)

Introduction: Drought stress is one of the most important abiotic stresses which significantly reduce yield and growth of most of plants. Plane tree is one of the important trees planted in the urban landscapes of Iran. One of the major limiting factors of landscapes development is providing water for plants. Deficit irrigation is a desirable method for saving water use in water deficit conditions and ultimately reducing necessary cost of water securement to landscape plants. Moreover, inoculation of plant root with mycorrhizal fungi can be considered as a method to reduce water demand of plants. In addition, mycorrhiza can increase plant resistance against environmental stress, such as salinity, temperature stress, drought stress and etc. Mycorrhiza can improve drought stress through enhancing water uptake as result of extra radical hyphae and stomatal regulation or transpiration. Increasing P concentration by mycorrhiza inoculation can be another mechansim for drought resistance in plants. The purpose of the present study was to evaluate two Glomus species in combination together on plane tree under water deficit for growth characteristics and nutrients uptake such as P, Fe and Zn concentration. Materials and Methods: This outdoor experiment was conducted at - Isfahan University of Technology, Isfahan, Iran, with average temperature 14.2 ºC and 27.9 ºC night/day, respectively and relative humidity 35-70% between Mar and Aug 2012 and repeated under the same condition in 2013. This experiment was carried out to evaluate the effect of inoculation with mycorrhizal fungus on plane saplings response to different applicable water levels (50 and 100% of water needs) based on a completely randomized design with 3 replications. The treatments were control (without fertilizer), Germans peat + fertilizer, Germans peat + fertilizer + mycorrhiza in 50% of field capacity and Germans peat + fertilizer + mycorrhizain 100% of field capacity. The Mycorrhiza fungi (mycorrhizal root, soil containing spore and extra radical mycelium) were obtained from Institute of Soil and Water Research (Tehran, Iran). There were inoculums treatments: two AM fungus inoculums (G. intraradices and G. mosseae) with combination of both. The inoculated dosage was approximately 80 spores g-1 for G. intraradices and 80 spores g-1 for G. mosseae, calculated by microscope before the experiment. Plants were irrigated daily base of 100% FC after the confidence of establishing plants about 2 months and then differential irrigations were applied. The amount of 100 and 50% ET was applied for full irrigation, moderate and serve deficit irrigation, respectively. To monitor the soil water content, tensiometry probe tubes were inserted into the soil in control pot around the root. Irrigation was performed whenever 40% of the available water was consumed. In order to calculate the amount of water necessary to bring each soil to FC, soil samples were collected and the water content determined by drying. Photosynthesis rate was measured with a LCI portable photosynthesis system. Soluble sugars measured according to Phenol–Sulfuric Acid method. Extraction of the Leaf chlorophyll pigments using with 100% acetone. The extraction of P, K, Fe, and Zn from the plant tissue material was performed by using dry ashing method. The mean data of two years were analyzed with SAS 9.1 software, the means were compared for significance by the least significant difference (LSD) test at P < 0.05. Results and Discussion: Mycorrhiza inoculation significantly increased fresh and dry weight, chlorophyll content, total sugar, leaf area, photosynthesis rate and P and K concentration as compared to control. As compared to the 100 and 50% FC, total chlorophyll, fresh and dry weight and P concentration significantly was increased in 100% FC (Table 4 & 5). The results showed that inoculation of plants with mycorrhizal fungus significantly increased most growth parameters including leaf area, chlorophyll content and leaf fresh and dry weight of plane saplings. Phosphorus content significantly increased in inoculated plants as compared to non-inoculated plants. It is recommended that in dry regions and water shortage conditions, the deficit irrigation method accompanied with mycorrhizal fungus inoculation to save water. Conclusion: Our data showed that mycorrhiza inoculations increased most growth parameters including leaf area, chlorophyll content and leaf fresh and dry weight of plane saplings. In conclusion, mycorrhiza inoculations can increase plant tolerance against drought stress by increasing phosphorus concentration, chlorophyll content, and photosynthesis rate. Generally, results of this study revealed that inoculation of plane tress with mycorrhizal fungi, improved plant growth under stress conditions through its positive influence on nutrients uptake, chlorophyll content and other growth parameters.