Waterlogging Signalling and Tolerance in Plants

In the last half century, because of the raising world population and because of the many environmental issues posed by the industrialization, the amount of arable land per person has declined from 0.32 ha in 1961-1963 to 0.21 ha in 1997-1999 and is expected to drop further to 0.16 ha by 2030 and therefore is a severe menace to food security (FAO 2006). At the same time, about 12 million ha of irrigated land in the developing world has lost its productivity due to waterlogging and salinity. Waterlogging is a major problem for plant cultivation in many regions of the world. The reasons are in part due to climatic change that leads to the increased number of precipitations of great intensity, in part to land degradation. Considering India alone, the total area suffering from waterlogging is estimated to be about 3.3 million ha (Bhattacharya 1992), the major causes of waterlogging include super- ous irrigation supplies, seepage losses from canal, impeded sub-surface drainage, and lack of proper land development. In addition, many irrigated areas are s- jected to yield decline because of waterlogging due to inadequate drainage systems. Worldwide, it has been estimated that at least one-tenth of the irrigated cropland suffers from waterlogging.

Part 1: Whole-plant regulation Oxygen Transport in Waterlogged Plants Lars Wegner 1.1 Introduction 1.2 O2 transport in plants: Some basic physics, and modeling of O2 diffusion 1.3 A survey of methods to study O2 transport and related parameters in higher plants 1.4 Anatomical adaptations to flooding stress: Barriers to radial oxygen loss 1.5 Anatomical adaptations to flooding stress: Formation of aerenchyma 1.6 Mechanisms of O2 transport in plants 1.7 O2 transport in plants: Ecological implications 1.8 Open questions and directions of further research 1.9 Acknowledgements 1.10 Literature cited Waterlogging and Plant Nutrient Uptake J. Theo M. Elzenga & Hans van Veen 2.1 Abstract 2.2 Introduction 2.3 Effects of hypoxia on nutrient uptake 2.3.1 Effects on root elongation and nutrient uptake capacity 2.3.2 Waterlogging effects on nutrient availability 2.3.3 Plant responses to waterlogging increasing uptake surface 2.3.4 Waterlogging decreases nutrient bulk flow 2.3.5 Changes in nutrient uptake kinetics 2.4 Summary and concluding remarks Strategies for Adaptation to Waterlogging and Hypoxia in Nitrogen Fixing Nodules of Legumes Daniel M. Roberts, Won Gyu Choi and Jin Ha Hwang Abstract 3.1 Introduction: The Oxygen Diffusion Barrier in Nodules 3.1.1 Nodule morphology and the gas diffusion barrier 3.1.2 Modulation of the gas diffusion barrier 3.1.3 Control of the gas diffusion barrier in response to sub-ambient O2 and flooding 3.1.4 Mechanism of regulation of the gas diffusion barrier in response to pO2 3.2 Developmental and morphological adaptations of nitrogen-fixing nodules to low oxygen stress 3.2.1 Secondary Aerenchyma Formation 3.2.2 The Inner Cortex and Infected Zone 3.2.3 Influence of adaptive changes on nitrogen fixation under altered rhizosphere pO2 conditions 3.3 Strategies of Adaptation: Flood-tolerant legumes and oxygen diffusion 3.3.1 Tropical wetland legumes 3.3.1.1 Nodulation of submerged stems and roots: increased porosity mechanisms 3.3.1.2 Aerial nodulation of stems and adventitious roots: avoidance mechanisms 3.3.2 Lotus uliginosus: a temperate wetland legume 3.4 Strategies of Adaptation: Alternate nodulation pathways for flooding tolerant legumes 3.4.1 Intercellular -based mechanism of nodulation: The Lateral Root Boundary Pathway 3.4.2 Sesbania rostrata: A model legume for aquatic nodulation 3.5 Summary and Concluding Remarks References Oxygen transport in the sapwood of trees Sergio Mugnai & Stefano Mancuso 4.1 Brief anatomy of a woody stem 4.2 The atmosphere inside a stem: gas composition and its effect on respiration 4.3 Gas transport and diffusion 4.4 Radial and axial oxygen transport to sapwood 4.5 Sapwood respiration References Part 2: Intracellular Signaling pH Signaling During Anoxia Hubert Felle Abstract. 5.1 Introduction 5.2 pH, signal and regulator 5.2.1 pH as systemic signal 5.2.2 The nature of the pH-transmission 5.2.3 What is the information? 5.3 Anoxic energy crisis and pH-regulation 5.3.1 The Davis-Roberts-hypothesis: aspects of pH signaling 5.3.2 Cytoplasmic acidification, ATP and membrane potential 5.3.3 Cytoplasmic pH (-change), an error signal? 5.4 pH-interactions between the (major) compartments during anoxia 5.4.1 The pH trans-tonoplast pH gradient 5.4.2 Cytoplasm and apoplast 5.4.3 The apoplast under anoxia 5.5 Anoxia tolerance and pH 5.5.1 pH as a stress signal - avoidance of cytoplasmic acidosis 5.6 pH as signal for gene activation 5.7 pH signalling ...