Tariq Aftab, PhD, is an assistant professor at Aligarh Muslim University, Aligarh, Uttar Pradesh, India. He has published over 100 research articles and edited 20 books with international publishers. He is the recipient of a prestigious Leibniz-DAAD fellowship from Germany, Raman Fellowship from the Government of India, and Young Scientist Awards from the State Government of Uttar Pradesh (India) and the Government of India. Kaiser Iqbal Wani, PhD, is a senior research fellow in the Department of Botany, Aligarh Muslim University, Aligarh, India. He is a recipient of a prestigious national fellowship CSIR/UGC JRF. He has several journal articles and book chapters to his name. His research focuses on molecular, proteomic, physiological, and biotechnological studies of medicinal plants under adverse environmental conditions.

• Preface xiii1 Strigolactones: Journey from Rhizospheric Chemoattractants to Plant Growth Regulators 1Kaiser Iqbal Wani, M. Naeem and Tariq Aftab1.1 Introduction 21.2 Brief History of Strigolactones 31.3 What is the Origin of the Name Strigolactone? 51.4 Diverse Strigolactone Functions: From Single-Celled Alga to Terrestrial Plants 51.5 Strigolactones in Ferns and Mosses: Rhizosphere Signals or Phytohormones? 61.6 Agricultural Loss and Root Parasitic Plants 71.7 Strigolactones and Agriculture: Why Do They Hold the Key? 9References 92 Nature, Structural Diversity, Biosynthetic Pathway, and Strigolactone Transport in Plants 13Ishrat Mehmood, Kaiser Iqbal Wani and Tariq Aftab2.1 Introduction 142.2 Chemical Nature of Strigolactones 152.3 Naming Protocol for Strigolactones 172.4 Natural Diversity of Strigolactones 182.4.1 Canonical Strigolactones 202.4.2 Non-Canonical Strigolactones 212.5 Biosynthetic Pathway of SLs 222.6 Strigolactone Transport 252.6.1 Movement of SL from Root to Shoot 252.6.2 Transport of SL via ABCG/PDR Pathway 272.7 Conclusion 28References 293 Unveiling the Strigolactone Signaling Pathway: From Receptors to Responses 35Rachel Helmich3.1 Introduction 363.2 The Strigolactone Perception 383.3 Strigolactone Signal Transduction 433.4 Transcriptional Regulation 483.5 Environmental Factors Modulate Strigolactone Signaling 513.6 Applications and Future Perspectives 543.7 Challenges and Unanswered Questions in Strigolactone Research 583.8 Conclusion 59References 604 Diverse Roles of Strigolactones in Plant Growth and Development: Shaping Above- and Below-Ground Architecture 69Alisha Hussain, Kaiser Iqbal Wani and Shahla Faizan4.1 Introduction 694.2 The Contribution of Strigolactones to Shoot Development 704.2.1 Bud Activation Dynamics in Arabidopsis via Auxin–Strigolactone Interplay 714.3 Role of Strigolactones in Regulating Shoot Secondary Growth 734.4 Root Development in Plants: Potential Role of Strigolactones 754.4.1 Primary Root Development 754.4.2 Lateral Root Initiation and Development 764.4.3 Root Hair Elongation 774.4.4 Adventitious Root Formation 784.4.5 Root Development in Response to Nitrogen and Phosphate Deficiencies 784.4.6 Strigolactone and Auxin Interplay During Root Development 794.4.7 Strigolactone and Cytokinin Interplay During Root Development 804.5 Role in Leaf Senescence 804.6 Conclusion 81References 815 Regulation of Phosphorus Nutrition in Tomato Plants: Unveiled Roles of Strigolactones 89Veronica Santoro, Michela Schiavon, Cristina Prandi and Luisella Celi5.1 Introduction 905.2 Strigolactone Chemistry and Biosynthesis 925.2.1 Structural Features and Classifications of Natural SLs 925.2.2 Synthetic Strigolactones 935.2.3 Biosynthetic Pathway 945.3 The SL Signaling Pathway 945.4 Function of Strigolactones in Tomato Plants: Emphasis on Phosphorus Nutrition 975.5 Conclusions 101References 1026 Strigolactones’ Role in Heat and Saline Stress Tolerance in Horticultural and Field Crops 109Juan Pablo Rodriguez, Jose Delatorre Herrera, Luisa Bascuñán and Enrique Ostria6.1 What are Strigolactones 1106.1.1 Endogenous Production Under Abiotic Stress 1116.1.2 Exogenous Use to Alleviate Abiotic Stress 1136.2 Production, Role, and Understanding of Strigolactones in Alleviating Heat Stress in Horticultural and Field Crops 1176.2.1 Morpho-Physiological Responses of Plants to Strigolactones 1196.2.2 Biochemical Attributes of Strigolactones in Alleviating Heat Stress in Horticultural and Field Crops 1206.2.3 Molecular Response of Strigolactones in Alleviating Heat Stress in Horticultural and Field Crops 1216.3 Production, Role, and Understanding of Strigolactones to Alleviate Salinity Stress in Horticultural and Field Crops 1226.3.1 Morpho-Physiological Responses of Plants 1226.3.2 Biochemical Responses at the Plant Level 1236.3.2.1 Ion Imbalance 1236.3.2.2 Osmotic Imbalance 1246.3.3 Molecular Response Level 1246.3.3.1 Strigolactones and Salinity 1246.4 Conclusions and Future Perspectives of Strigolactones’ Use for Alleviating Stress in Plants 127References 1277 Role of Strigolactones in Heavy Metal Tolerance: A Case Study on Cadmium 137Ishrat Mehmood, Kaiser Iqbal Wani and Tariq Aftab7.1 Introduction 1387.2 Cadmium Toxicity on Plants 1397.2.1 cd Toxicity on Growth and Development 1397.2.2 cd Toxicity Induces Oxidative Damage 1407.2.3 Impaired Photosynthetic and Respiratory Activity 1417.2.4 cd Toxicity on Nutrient Uptake and Plant–Water Relations 1427.2.5 cd Toxicity on Seed Germination 1427.2.6 cd Toxicity on Amino Acids and Proteins 1437.3 Strigolactone-Mediated Cadmium Tolerance 1447.3.1 Strigolactones Enhance Cd Tolerance by Boosting Antioxidant Defense Mechanisms 1447.3.2 Regulatory Role of SLs in Photosynthesis for Improving Cadmium Tolerance 1467.3.3 Potential Role of SLs in Improving NO Signaling Under Cadmium Stress 1477.3.4 Potential Role of SLs in Regulating Root and Shoot Architecture Under Cadmium Stress 1487.4 Future Perspectives and Challenges of SLs for Agricultural Practices and Environmental Sustainability 1497.5 Conclusion 151References 1518 Strigolactone Interplay with Other Phytohormones Under Stressed and Normal Conditions 161Ishrat Mehmood, Kaiser Iqbal Wani and Tariq Aftab8.1 Introduction 1628.2 Role of SLs in Abiotic Stress Tolerance 1628.2.1 SLs During Nutrient Starvation 1638.2.2 SLs During Drought Stress 1658.2.3 SLs During Salinity Stress 1668.2.4 SLs During Light Stress 1688.2.5 SLs During Heat Stress 1698.2.6 SLs During Chilling Stress 1708.2.7 SLs During Heavy Metal Stress 1718.3 Interplay of SLs with Other Phytohormones 1728.3.1 Crosstalk Between SLs and Abscisic Acid 1728.3.2 Interplay of SLs with Jasmonic Acid 1738.3.3 SLs and Salicylic Acid Crosstalk 1748.3.4 Integration of SLs with Ethylene Signaling 1748.3.5 Strigolactones and Gibberellins 1768.3.6 Cross-Talk Between SLs and Auxins 1778.3.7 Emerging Perspectives on SLs and Cytokinins 1788.4 Future Directions and Implications for Agriculture 1808.5 Conclusion 181References 1819 Strigolactone Analogs: Synthesis, Structural Features and Biological Activity 193Roheela Ahmad, Pirzada Mohammad Haris, Zubair Altaf Reshi, Tahir Ahmad Sheikh, Ayman Javed and Inayat Mustafa Khan9.1 Introduction 1949.2 Synthesis of Natural SLS 1959.2.1 Introduction to Synthesis 1959.2.2 Attachment of the D-Ring 1969.2.3 Modification of the D-Ring and Side Chains 1969.2.4 Examples of Total Synthesis 1969.2.5 Lessons Learned from Total Synthesis 2009.3 Structures of Strigolactones 2019.3.1 Essential Structural Features and Structural Diversity 2019.4 Biological Activity of Strigolactones 2039.4.1 Germination Stimulation Activity 2039.4.2 Hyphal Branching 2049.4.3 Shoot Branching Inhibition 2049.5 Conclusion 205References 20510 Karrikin-Related Effects on Plant Development, Stress Tolerance, and Beyond 211Tamás Bodor, Gábor Fejes, Dóra Kondak, Selahattin Kondak, Réka Szőllősi and Zsuzsanna Kolbert10.1 Introduction 21210.2 Direct KAR-Associated Effects on Plants 21510.2.1 Promotion of Seed Germination and Seedling Growth in Healthy Plants 21510.2.2 Amelioration of Abiotic Stress-Related Damages 21910.2.2.1 Drought Stress 21910.2.2.2 Temperature Stresses 22110.2.2.3 Salinity 22210.2.2.4 Heavy Metals 22310.2.3 Amelioration of Biotic Stress-Induced Damages 22310.3 Indirect KAR-Associated Effects on Plants 22410.4 Smoke Water as a Promising Agent for Agricultural Applications 22510.5 Conclusions and Perspectives 228Acknowledgments 228References 22811 Strigolactones: Key Phytohormones in Plant–Microbe Interactions and Development 235Asif Hussain Hajam and Gausiya Bashri11.1 Introduction 23611.2 Identification of SLs as Signaling Molecules in AM Symbiosis 23711.3 SL Perception by AM Fungi 23811.4 Influence of SLs on AM Fungi at the Cellular and Molecular Levels 23811.5 SLs and AM Fungi Mediate Root Development 23911.6 Impact of AM Fungi on Nutrient Acquisition (Particularly Phosphate) and Plant Growth 24111.7 AM Symbiosis: Serving as a Biofertilizer and Biocontrol Agent 24311.8 Interactions of SL with Non-AM Fungi 24411.9 Strigolactones and Root Nodule Symbiosis 24511.10 Effect of SLs on Nodule Number (Quantity) 24711.11 Impact of SLs on Rhizobia 24911.12 Future Directions and Conclusion 250References 25212 Strigolactones and Control of Parasitic Weeds 261Sonal Jain, Rahul Kumar, Divya Gunsola, Sanja Živković, Tanja Vasić, Sourav Chattaraj, Somya Sinha, Prateek Gururani, Shraddha Bhaskar Sawant, Guerra Sierra B.E., Wiem Alloun and Debasis Mitra12.1 Introduction 26212.2 What are SLs? 26312.2.1 Stimulation of Seed Germination 26312.2.2 Inhibition of Shoot Branching 26312.2.3 Influence on Root Development 26412.2.4 Response to Stress 26412.3 Phenomena of Host–Parasitic Plant Interaction 26512.4 SL–Carotenoid/Biosynthetic Pathway for Stimulation 26712.4.1 The Role of Carotenoid 26712.4.2 Isomerization by D 27 26712.4.3 Cleavage by CCD7 and CCD 8 26712.4.4 Oxidation by Cytochrome P450 Enzymes 26712.4.5 LBO and Unknown Enzymes 26812.5 Karrikins 26812.6 Exploring Various Strategies for Controlling Parasitic Weed Infestations 26812.6.1 Involvement of SL Biosynthesis Inhibitors 26812.6.2 Genetic Manipulation 26912.6.3 Application of Synthetic SLs, Mimics, and Analogues/Suicidal Germination Strategy for Parasitic Weed Control 27012.7 Impact of SL Application on Future Scientific Research and Agriculture 27112.8 SL Functions 27512.9 Conclusion 275References 27613 Strigolactones and Plant Defense: Protection Against Pests and Pathogens 281Bonia Francis, C. T. Aravindakumar and Sibu Simon13.1 Introduction 28213.2 Biotic Stresses in Plants 28313.3 Biotic Stress-Mediated Defense Mechanism in Plants 28413.4 Strigolactone-Mediated Defense Against Pathogens 28813.5 Strigolactone-Mediated Defense Against Pests 29013.6 Strigolactone-Mediated Plant Defense Mechanism 29013.7 Conclusion and Future Perspective 292Acknowledgment 292References 292Index 301