Effect of Three Species of Arbuscular Mycorrhizal Fungi on some Physiological and Growth Characteristics of Peach Seedlings under Drought Stress Conditions

Abstract

IntroductionSince Iran is one of the arid and semi-arid regions of the world and due to the great importance of water in agriculture, it is very important to conduct research to improve drought stress in order to produce more quality products. In this regard, this study was conducted to investigate the effect of mycorrhiza species on some morphological and physiological characteristics of peach seedlings under drought stress. Arbuscular mycorrhizal fungi coexist with the roots of various plants and have a broad effect on their growth. These fungus are effective in the initial establishment of the plant under drought conditions. Arbuscular mycorrhizal fungi increases plant resistance to dehydration by increasing growth and uptake of nutrients, especially phosphorus. Matherials and MethodsIn order to investigate the effect of three species of Arbuscular mycorrhizal fungi on some vegetative characteristics and phosphorus absorption of peach seedlings under drought stress conditions, a factorial experiment was conducted based on a randomized complete block design with four replications. The experimental factors included: drought stress at four levels (100, 80, 60 and 40 percent of field capacity) and the second factor application of mycorrhizal fungus at four levels: application of three species of mycorrhiza fungi and three species of fungi, each in three concentration (75, 100, 125 g in a pot) with chemical fertilizer (100 g triple super phosphate for each pot) and fertilizer (without mycorrhiza) and control (without fertilizer and mycorrhiza). The measurements were comprised root traits, stem diameter, vegetative growth of branches, leaf area index, vegetation index, relative leaf water content, chlorophyll fluorescence, leaf electrolyte leakage, leaf phosphorus and colonization root percent. Results and DiscussionResult showed that application of mycorrhizal fungi seems to be effective in reducing the effects of dehydration stress. The use of these fungi had a positive effect on reducing leaf electrolyte leakage under severe dehydration. According to the results obtained in this experiment, the highest efficiency in drought stress conditions was observed in G. mosseae and G. intraradices. Under drought stress conditions, the lowest values of root volume, greenness index, chlorophyll fluorescence, leaf electrolyte leakage, root colonization and leaf phosphorus content were observed. With increasing of drought stress, all of the mentioned traits reduced and mycorrhiza fungi had a positive significant effect on all studied traits. In this study, it was found that with increasing stress intensity, the traits were negatively affected and led to irreparable damage to the product. Therefore, it is expected that by preventing or minimizing the effects of stress, an effective step was taken to increase performance. The significant decrease in root colonization with increasing stress is probably due to the decrease in the growth of hyphae. The most important step after spore germination is the growth of hyphae resulting from germination, which plays an essential role in root colonization. Apparently, hyphae growth is more affected by osmotic potential than spore growth. The results obtained from this research showed that the roots of peach seedlings have significant symbiosis potential with arbuscular mycorrhizal fungi (Peymaneh & Zarei, 2013). According to Miyashita et al. (2005) Leaf photosynthesis activity can be used as a useful tool for classification of drought tolerant plants. Sajjadinia et al. (2010) regarding the relative water content and photosynthesis of several pistachio cultivars reported high correlation and high diversity in different stages and cultivars and stated that the decrease in relative water content strongly reduces transpiration, stomatal conductance and photosynthesis, which our results are consistent. With the escalation of tension, the greenness index also decreased; So that in the conditions of severe stress (40% of crop capacity), the amount of greenness index reached the lowest value. In the conditions of severe stress due to interruption of continuous irrigation, the plants entered from the stage of mild stress to the stage of severe dry stress, which seems that under these conditions, the decrease in the concentration of chlorophyll, in addition to the decrease in the amount of synthesis, is caused by the decomposition of chlorophyll due to the increase in the amount chlorophyllase, peroxidase and phenolic compounds. According to Schutz and Fangmier (2001), the decrease in the amount of chlorophyll in stress conditions is related to the increase in the production of oxygen radicals in the cell. These free radicals cause peroxidation and as a result the decomposition of this pigment. The greenness index is considered one of the most important growth parameters, which is reduced by drought stress conditions, and the results indicate that the treatment of mycorrhizal fungi in all three types of inoculated mushrooms has improved the greenness index and the adverse effects It has removed the drought stress to a great extent (Figure 6), which can be attributed to the improvement of water and food absorption by mycorrhizal roots (Larsson et al., 2008). Conclusion In general, this study showed that the best treatment related to the mycorrizha fungi was mosseae, which had the most effect on reducing the negative effects of stress

Keywords

• chlorophyll fluorescence
• cholorophyll index
• electrolyte leakage
• root colonization
• root volume