Osmotic drought stress influence on physiological and biochemical characteristics of pistachio (Pistacia spp.) seedlings Ali Esmaeilpour . In The Name Of Allah, The Most Beneficent, The Most Merciful Promotors: Prof. dr. ir. Patrick Van Damme, Laboratory of Tropical and Subtropical Agronomy and Ethnobotany, Department of Plant Production, Faculty of Bioscience Engineering, Ghent University, Belgium Prof. dr. ir. Roeland Samson, Department of Bioscience Engineering, Faculty of Science, Antwerp University, Belgium Faculty of Bioscience Engineering Dean: Prof. dr. ir. Marc Van Meirvenne Rector: Prof. dr. Anne De Paepe Ali Esmaeilpour Osmotic drought stress influence on physiological and biochemical characteristics of pistachio (Pistacia spp.) seedlings Thesis submitted in fulfilment of the requirements for the degree of Doctor (PhD) in Applied Biological Sciences This work should be cited as: Esmaeilpour, A. 2017. Osmotic drought stress influence on physiological and biochemical characteristics of pistachio (Pistacia spp.) seedlings. PhD thesis, 181 pp, Ghent University, Ghent, Belgium. Copyright: The author and the promoters give the authorization to consult and to copy parts of this work for personal use only. Every other use is subject to the copyright laws. Permission to reproduce any material contained in this work should be obtained from the author. ISBN- number: 9789463570442 Cover illustration: Front page: Adult pistachio tree Back page: Top left: male flowers Middle left: female flowers Top right: ripen fruits Bottom left: fruits in shell Bottom right: pistachio kernels Members of the jury Prof. Jo Dewulf (Chairman) Department of Sustainable Organic Chemistry and Technology Faculty of Bioscience Engineering, Ghent University Prof. Kathy Steppe (Secretary) Department of Applied Ecology & Environmental Biology Faculty of Bioscience Engineering, Ghent University Prof. Marie-Christine Van Labeke Department of Plant Production Faculty of Bioscience Engineering, Ghent University Dr. ir. Karen Wuyts Department of Bioscience Engineering Faculty of Science, Antwerp University Dr. ir. Wouter Maes Department of Applied Ecology & Environmental Biology Faculty of Bioscience Engineering, Ghent University Dr. ir. Wouter Vanhove Department of Plant Production Faculty of Bioscience Engineering, Ghent University Prof. Patrick Van Damme (Promotor) Department of Plant Production Faculty of Bioscience Engineering, Ghent University Prof. Roeland Samson (Promotor) Department of Bioscience Engineering Faculty of Science, Antwerp University Acknowledgements First of all, I am grateful to The Almighty God for establishing me to complete this research. This thesis would not have been possible without the support of many people. I would like to express my deepest appreciation to my first promotor, Prof. dr. ir. Patrick Van Damme, for his constant support, guidance and valuable comments through the period of this study. I am very grateful to my other promoter, Prof. dr. ir. Roeland Samson from Antwerp University for his great comments and also his support for providing all devices that I required to measure some data parameters during my research in his laboratory thanks also to his colleagues for helping me in this project. I would also like to thank Prof. dr. ir. Marie-Chrisitine Van Labeke, who advised my research in the best way at horticulture laboratory. She provided me with all the facilities that I needed in my research and I am deeply thankful to her and her colleagues in this laboratory for their great expertise and contribution to my research. I am very thankful to the director of Iran’s Pistachio Research Institute (IPRI) and Agricultural Research, Education and Extension Organization (AREEO) of Iran for awarding me a scholarship for doing this PhD research. I would like to thank former rector of Ghent University Prof. dr. Paul Van Cauwenberge, dean of bioscience faculty Prof. dr. ir. Guido Van Huylebroeck and Head of Laboratory of Tropical and Subtropical Agriculture and Ethnobotany Prof. dr. ir. P. Van Damme for accepting me as a doctoral student. I am deeply grateful to Prof. dr. ir. P. Van Damme and Prof. dr. ir. Van Labeke for their invaluable assistance and remarks during the course of writing my thesis and publications. I am very grateful, for the help and hospitality of the staff in the Laboratory of Tropical and Subtropical Agriculture and Ethnobotany, Ghent University: Johan Geirnaert, who assisted me during all glasshouse experiments and solved my technical problems, dr. ir. Wouter Vanhove, dr. ir. Celine Termote, ir. Kaat Verzelen, ir. Arne Baert, dr. ir. Hannes Cosyns and Isabel Vandriessche who helped me during my study here. I take this opportunity to record our sincere thanks to all my colleagues in the laboratory of Horticulture in the Department of Plant Production in Ghent University; ir. Katrien De Dauw, Mieke, Thea and Christophe thanks to you all for your kind help and support. I would like to thank Prof. dr. ir. Pascal Boeckx and Katja Van Nieuwland, laboratory of Isotope Bioscience–ISOFYS, Ghent University, who assisted me in measuring carbon and nitrogen isotope contents in plant samples. I would like to thank Nafiseh (my daughter) for translating the summary to Dutch and also Dr. ir. Wouter Vanhove who did scientific editing of the Dutch summary. I also place on record my sense of appreciation to all of my colleagues in Iran’s Pistachio Research Institute: dr. ir. H. Hashaminasab, dr. ir. A. Javanshah, dr. ir. H. Hokmabadi, dr. ir. A.H. Mohamadi, dr. ir. M.R. Mehrnejad, dr. ir. M. abdolahi, dr. ir. B. Panahi, ir. Akbar Mohamadi and ir. M. Heidari and other my colleagues who directly or indirectly have lent their helping hand in this venture. I greatly appreciate the help, co-operation and friendship of all my Iranian friends in Gent: dr. ir. M. Mohammadimasoudi, dr. ir. Meisam Rezaei, ir. S. Safari, Mrs. Tahera Safari, ir. Siamak Ghafaripour (God bless him), dr. ir. K. Mehdikhanlo, dr. ir. A. Jahanshahi, ir. A. Fardis, dr. ir K. Mahdian and dr. ir Z. Aazami. I wish to express my eternal gratitude to my parents and my parents in laws who have always been faithful supporters to my life and education. Finally, I would like to express my special gratitude to my wife “Maryam” for all her support, taking care of me and our children. She has patiently endured; many long hours at home, alone with the kids, teach my younger daughter while I worked on my thesis. Nafiseh our wonderful daughter thank you for all your patient and efforts, I know your studding here were so difficult because you did not know Dutch and French languages before our coming but you tried hard to learn them in a very short time and entered to regular high school, got diploma, passed the medicine exam successfully and studied in the university eagerly. But, my very cute child, Nazanin as you were very young when we came here, I believe new school, new language, new friends and travel to Brussel every day were so difficult to do, but you incredibly did all these hard conditions without any complain once. I would like thanks again for you all for your help and co-operation during my studies. From now on, I promise to be with you all time everywhere. Regards, Ali Esmaeilpour Ghent, Belgium October 2017 Summary Summary Pistachio belongs to the Anacardiaceae family. Only Pistacia vera L., i.e. cultivated pistachio, has economic importance. Iran, as the region of origin of pistachio, has always had the largest cultivation area in the world. About 80 percent of Iran is categorized as semi-arid and arid. In Iran, pistachios are usually cultivated under dry and saline conditions as they have a high drought and salinity tolerance. Still, water deficit and salinity can cause a reduction in growth, yield and nut quality. Drought stress adversely affects growth, dry mass accumulation, and productivity of plants, and causes a higher rate of impairment than any other environmental factor. There is wide variation in edible pistachio (P. vera) cultivars in Iran which are grown under different environmental conditions. Yet, physiological responses of some pistachio cultivars and rootstocks to drought stress have hardly been studied. The aim of this study was to evaluate the effects of osmotic drought stress and subsequent recovery on physiological performance of three pistachio rootstocks (P. vera L. cv. Badami, P. vera L. cv. Sarakhs and P. terebinthus) and three of the country’s most common P.vera cultivars (Akbari, Kaleghochi and Ohadi). In this respect, we conducted two experiments during a two years period in the glasshouse in Ghent, Belgium. In the first year, three pistachio rootstocks, i.e., P. vera L. cv. Badami, P. vera L. cv. Sarakhs and P. terebinthus were subjected to four osmotic drought stress treatments: -0.1 (control), -0.5, -1.0 and -1.5 MPa using PEG 6000. Results obtained from this experiment (Chapter 3) indicate that all drought stress treatments decreased maximum quantum yield of PSII (Fv/Fm), effective PSII quantum yield (YII) and photochemical quenching (qP). A decreasing osmotic potential of the nutrient solution significantly decreased leaf phosphorous (P) concentration compared to control plants. Effects of rootstocks on leaf mineral element contents varied significantly with drought stress condition. Drought stress significantly decreased both plant fresh and dry weight, shoot and root dry weight, leaf area and stem elongation. There was also a significant rootstock effect on these growth parameters under drought stress condition. Under osmotic stress treatments, root/shoot ratio increased significantly. Control plants showed normal elongation growth, but growth was stopped with all drought stress treatments, and differences were significant for all three rootstocks. After two weeks of stress, a recovery of 2 weeks was applied. This period was insufficient to fully restore the negative effects of the applied severe stress on the studied rootstocks. i Summary The applied osmotic drought stress on pistachio rootstocks induced significant reductions in chlorophyll fluorescence parameters, reduction in leaf nutrient content and increases in the leaf carbon isotope composition in pistachio rootstocks.