University of Isfahan Journal of Plant Biological Sciences 3041-9603 15 3 2024 10 09 Effects of bio-organic fertilizers and foliar application of zinc and putrescine on chlorophyll fluorescence indices and some physiological traits of barley (Hordeum vulgare L.) under water limitation conditions Effects of bio-organic fertilizers and foliar application of zinc and putrescine on chlorophyll fluorescence indices and some physiological traits of barley (Hordeum vulgare L.) under water limitation conditions 115 145 28612 10.22108/ijpb.2024.140572.1356 FA Mohammadi Kale Sarlou Sara Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran. Raouf Seyed Sharifi Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran. Mohammad Sedghi Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran. Journal Article 2024 01 28 To study the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions, a factorial experiment was conducted based on randomized complete block design with three replications at the research greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili in 2022. The experiment factors included irrigation levels (full irrigation as a control, irrigation withholding at 50% of booting and heading stages, as moderate and severe water limitation respectively equivalent to BBCH 43 and 55),  application of bio-organic fertilizers in four levels (no application as a control, application of vermicompost, mycorrhiza, both application of vermicompost and mycorrhiza), foliar spraying of putrescine and nano zinc oxide in four levels (foliar spraying with water as a control, foliar spraying 0.4 g.L-1 nano zinc oxide, 0.8 mM putrescine, foliar spraying zinc, and putrescine). The results showed that application of stress modulators (vermicompost, mycorrhizal, zinc and putrescine) under severe water limitation (irrigation withholding at 50% of booting) increased chlorophyll index (34.06%), flag leaf nitrogen index (24.19%), maximum fluorescence (77.73%), quantum yield (80.38%), stomatal conductance (62.88%) and relative water content (50.99%) in compared to the no application of stress modulators in the same level from irrigation levels. Also under severe water limitation, the lowest minimum fluorescence (137.8) and electrical conductivity (90.07 μS.m^-1) were obtained at the application of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide). Based on the results of this study, irrigation withholding at 50% of booting and no application of stress modulators decreased 25% grain yield of barley compared to the application of stress modulators in the same level of irrigation levels and application of stress modulators were able to compensate for part of this reduction in grain yield.<br /><strong>Introduction</strong><br />Drought is the most severe abiotic stress factor limiting plant growth and crop production. Drought stress decreases the yield of many crops by inhibiting plant photosynthesis and photosystem II efficiency. Mycorrhiza application is a strategy that can improve plant performance under stress environments and, consequently enhance plant growth through different mechanisms. The mechanisms used by mycorrhiza to enhance the water relations of host plants are not amply clear, however, this may occur by increasing water absorption by external hyphae, regulation of stomatal apparatus, increase in activity of antioxidant enzymes, and absorption of nutrients, particularly phosphorus. Also, vermicompost can directly increase plant production through increasing available plant nutrients and indirectly promote soil quality by improving soil structure and stimulating microbial activities, relative to conventional chemical fertilization. Putrescine is a polyamine that has a protective role in plants. Zinc deficiency is recognized as a critical problem in plants, especially grown in saline conditions with high pH values. However, plant growth and production can be improved by foliar application of nano zinc oxide. Zinc application significantly reduced the negative effects of droughts on plants by reducing photo-oxidative damage. So, this study aimed to investigate the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions.<br /><strong>Material and Methods</strong><br /> To study the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions, a factorial experiment was conducted based on randomized complete block design with three replications at the research greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili in 2022. The experiment factors included irrigation levels (full irrigation as a control, irrigation withholding at 50% of booting and heading stages, as moderate and severe water limitation respectively equivalent to BBCH 43 and 55),  application of bio-organic fertilizers in four levels (no application as a control, application of vermicompost, mycorrhiza, both application of vermicompost and mycorrhiza), foliar spraying of putrescine and nano zinc oxide in four levels (foliar spraying with water as a control, foliar spraying 0.4 g.L^-1 nano zinc oxide, 0.8 mM putrescine, foliar spraying zinc, and putrescine).<br /><strong>Results and Discussion</strong><br />The results showed that the application of stress modulators (vermicompost, mycorrhizal, nano zinc oxide, and putrescine) under severe water limitation (irrigation withholding at 50% of booting) increased chlorophyll index (34.06%), flag leaf nitrogen index (24.19%), maximum fluorescence (77.73%), quantum yield (80.38%), stomatal conductance (62.88%) and relative water content (50.99%) in compared to the no application of stress modulators in the same level from irrigation levels. Also under severe water limitation, the lowest minimum fluorescence (137.8) and electrical conductivity (90.07 μS.m^-1) were obtained at the application of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide). Based on the results of this study, irrigation withholding at 50% of booting and no application of stress modulators decreased 25% grain yield of barley by compared to the application of stress modulators in the same level from irrigation levels and application of stress modulators were able to compensate for part of this reduction in grain yield.<br /><strong>Conclusion</strong><br />It seems that the application of biofertilizers and foliar application of putrescine and zinc nano oxide under water limitation conditions were able to compensate for part of this reduction in grain yield by improving the chlorophyll fluorescence indices and some physiological traits.<br /><strong>Acknowledgments: </strong>Funding for the present research was provided by Mohaghegh Ardabili University of Iran. The authors gratefully acknowledge the Mohaghegh Ardabili University. To study the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions, a factorial experiment was conducted based on randomized complete block design with three replications at the research greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili in 2022. The experiment factors included irrigation levels (full irrigation as a control, irrigation withholding at 50% of booting and heading stages, as moderate and severe water limitation respectively equivalent to BBCH 43 and 55),  application of bio-organic fertilizers in four levels (no application as a control, application of vermicompost, mycorrhiza, both application of vermicompost and mycorrhiza), foliar spraying of putrescine and nano zinc oxide in four levels (foliar spraying with water as a control, foliar spraying 0.4 g.L-1 nano zinc oxide, 0.8 mM putrescine, foliar spraying zinc, and putrescine). The results showed that application of stress modulators (vermicompost, mycorrhizal, zinc and putrescine) under severe water limitation (irrigation withholding at 50% of booting) increased chlorophyll index (34.06%), flag leaf nitrogen index (24.19%), maximum fluorescence (77.73%), quantum yield (80.38%), stomatal conductance (62.88%) and relative water content (50.99%) in compared to the no application of stress modulators in the same level from irrigation levels. Also under severe water limitation, the lowest minimum fluorescence (137.8) and electrical conductivity (90.07 μS.m^-1) were obtained at the application of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide). Based on the results of this study, irrigation withholding at 50% of booting and no application of stress modulators decreased 25% grain yield of barley compared to the application of stress modulators in the same level of irrigation levels and application of stress modulators were able to compensate for part of this reduction in grain yield.<br /><strong>Introduction</strong><br />Drought is the most severe abiotic stress factor limiting plant growth and crop production. Drought stress decreases the yield of many crops by inhibiting plant photosynthesis and photosystem II efficiency. Mycorrhiza application is a strategy that can improve plant performance under stress environments and, consequently enhance plant growth through different mechanisms. The mechanisms used by mycorrhiza to enhance the water relations of host plants are not amply clear, however, this may occur by increasing water absorption by external hyphae, regulation of stomatal apparatus, increase in activity of antioxidant enzymes, and absorption of nutrients, particularly phosphorus. Also, vermicompost can directly increase plant production through increasing available plant nutrients and indirectly promote soil quality by improving soil structure and stimulating microbial activities, relative to conventional chemical fertilization. Putrescine is a polyamine that has a protective role in plants. Zinc deficiency is recognized as a critical problem in plants, especially grown in saline conditions with high pH values. However, plant growth and production can be improved by foliar application of nano zinc oxide. Zinc application significantly reduced the negative effects of droughts on plants by reducing photo-oxidative damage. So, this study aimed to investigate the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions.<br /><strong>Material and Methods</strong><br /> To study the effects of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide) on chlorophyll fluorescence indices and some physiological traits of barley under water limitation conditions, a factorial experiment was conducted based on randomized complete block design with three replications at the research greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili in 2022. The experiment factors included irrigation levels (full irrigation as a control, irrigation withholding at 50% of booting and heading stages, as moderate and severe water limitation respectively equivalent to BBCH 43 and 55),  application of bio-organic fertilizers in four levels (no application as a control, application of vermicompost, mycorrhiza, both application of vermicompost and mycorrhiza), foliar spraying of putrescine and nano zinc oxide in four levels (foliar spraying with water as a control, foliar spraying 0.4 g.L^-1 nano zinc oxide, 0.8 mM putrescine, foliar spraying zinc, and putrescine).<br /><strong>Results and Discussion</strong><br />The results showed that the application of stress modulators (vermicompost, mycorrhizal, nano zinc oxide, and putrescine) under severe water limitation (irrigation withholding at 50% of booting) increased chlorophyll index (34.06%), flag leaf nitrogen index (24.19%), maximum fluorescence (77.73%), quantum yield (80.38%), stomatal conductance (62.88%) and relative water content (50.99%) in compared to the no application of stress modulators in the same level from irrigation levels. Also under severe water limitation, the lowest minimum fluorescence (137.8) and electrical conductivity (90.07 μS.m^-1) were obtained at the application of stress modulators (vermicompost, mycorrhiza, and foliar application of putrescine and nano zinc oxide). Based on the results of this study, irrigation withholding at 50% of booting and no application of stress modulators decreased 25% grain yield of barley by compared to the application of stress modulators in the same level from irrigation levels and application of stress modulators were able to compensate for part of this reduction in grain yield.<br /><strong>Conclusion</strong><br />It seems that the application of biofertilizers and foliar application of putrescine and zinc nano oxide under water limitation conditions were able to compensate for part of this reduction in grain yield by improving the chlorophyll fluorescence indices and some physiological traits.<br /><strong>Acknowledgments: </strong>Funding for the present research was provided by Mohaghegh Ardabili University of Iran. The authors gratefully acknowledge the Mohaghegh Ardabili University. https://ijpb.ui.ac.ir/article_28612_8d3f0295e570304299f877edf1cf2da0.pdf