Preface The idea of the book is to help researchers and progressive farmers to put into practice the outcome of dedicated and conscientious research in some lesser applied and very practical fields of plant physiology. Information on the innate ability of the plant system to imbibe the different cues of nature and respond in ways, which have been considered allegoric have now been unraveled with advancement in technology. Many assumptions have been redefined with a strong scientific base. This book contains seven chapters compiled by researchers working in the field of plant physiology; viz. (1) “Plant plasticity: concepts and recent advances”- meant to acquaint the reader with the capacity of the plant to mould its physiological processes and growth in accordance with the environment; (2) “Plant acoustic responses-concept and significance”- dealing with the response of plants to different types of sound, both natural and man-made; (3) “Spectral manipulation of plant responses”light being a major constraint in productivity can have a major stake in improving yield potential especially in polyhouse cultivation; (4) “Geomagnetic responses in plants”- the inf luence of geomagnetism on plant life needs greater emphasis as this information may help to devise better management practices in crop production; (5) “Electricity from living plants-myth or reality”- highlighting clean energy as the need of the hour by utilizing green plants to produce electricity and to run electronic devices which needs further elucidation and encouragement; (6) “Plant architecture-evolution, diversity, regulation and scope”- manipulating plant growth for aesthetic value is a common practice but utilizing the same green architecture for utility is a more recent concept; (7) “Plant neurobiology-a paradigm shift in plant science”- a new branch of plant communication which is being recognized by plant scientists.

Introduction Plasticity is a unique attribute by which the otherwise sessile plant species are capable of adjusting to environmental vagaries by changing their phenotypic and morphological characters. Any plant population will be able to survive only if it can respond to an extremely variable environment by becoming more plastic and more genetically variable. To achieve this, plants should be able to suitably change their morphology anatomy and physiology or any one of these parameters based on environmental changes so as to improve their adaptability and survival in the altered environment. When such changes are genetically heritable, then they lead to species evolution. Plasticity helps plants to adapt to new environmental conditions, after migration to new geographical areas, by genetic assimilation of traits that can help to improve their performance under a new set of conditions. Understanding plasticity is important for predicting and managing the effect of climate change on native species as well as crop plants. Response of plants to modified environmental conditions is critical for their persistence. Phenotypic plasticity has been defined as the ability of an individual genotype to produce different phenotypes when exposed to different environmental conditions (Pigliucci et al., 2006). This includes the ability of a plant to modify its development in response to environmental cues and also its ability to bring about changes in its metabolism which increases the chances of survival of an organism under a specific condition.

Introduction Plants possess complex, systematic and specific mechanisms to cope up with abiotic as well as biotic stresses in the existing environment. ‘Do plants respond to sound ? How can plants perceive sound without a hearing organ?’- are interesting queries among the scientific community. Responses of plants to different factors such as temperature, moisture, light, wind, pests and microbes are well understood. However, information on the effects of audible sound frequencies on plants are still lacking. Recent evidences suggest that audible sound stimulation can contribute to better plant growth and improved quality of plant produce. It also represents a new trigger for plant protection. Sound is an acoustic energy in the form of a mechanical wave which transmits through gases, liquids and solids. Acoustic spectrum consists of three regions, infra sound (less than 20 Hz), audible region (20-20,000 Hz) and ultrasound (greater than 20,000 Hz). Infra sound and ultrasound are used in clinical diagnosis and therapeutics. Research on plant responses towards different stimuli started during 1880s by Charles Darwin. In 1848, Dr. Gustav Theodor Fechner, a German experimental psychologist, suggested that plants are capable of feeling emotions and that one could promote healthy growth of plants with talk, attention, attitude and affection. Later, J. C. Bose (1926), famous Indian botanist and physicist, made several studies on the effect of sound vibrations on plants. According to him, a plant treated with care and affection gives out a different vibration than a plant subjected to torture. In addition, Bose found that plants grew more quickly in pleasant music and more slowly in loud noise or harsh sounds. He also noticed that plants can “feel pain and understand affection” based on variation of cell membrane potential under different sound frequencies. Retallack (1973) also described several experiments involving plants and music.

Introduction The ultimate aim of agricultural research or any other related activity is to increase yield. Yield improvement could be obtained mainly through the enhancement of photosynthetic efficiency. Photosynthesis is a process in which plants convert light energy to chemical energy. Sun is the ultimate source of energy for photosynthesis. However only half of the total solar radiation (51%) reaches the earth’s surface of these only 1.2% reaches the plant canopy. Solar spectrum contains an array of other radiations which can be harmful for plant and human life. With increasing global climatic change amount of harmful radiation reaching the earth’s surface has increased and this is found to influence plant productivity. Under this scenario, protected cultivation is gaining popularity in many countries as it helps to reduce harmful effects of undesirable radiation, to allow cultivation of crops irrespective of seasons and also expand cultivation to non-traditional areas by artificially manipulating crop environment. In this context, spectral manipulation for crop production has emerged as an important area in crop production system

Introduction Earth’s magnetic field (MF) is a natural component of environment and is an inescapable factor for all living organisms including plants. Earth has an inner core made of molten iron which rotates at a fairly high speed creating a magnetic field just like a dynamo. This Geo Magnetic Field (GMF) extends from the earth’s interior into outer space. It interacts with the solar wind, which is actually a stream of charged particles emanating from the sun. As earth is engulfed in a GMF, all living organisms, both plants, animals and all biological processes are under its influence. However, local differences in strength and direction of the geomagnetic field have been detected. The vertical component of GMF is maximum at the magnetic poles, which is around 67 μT, and the horizontal component is zero there. Conversely, at the magnetic equator the vertical component is zero and the horizontal component is maximum, about 33 μT (Kobayashi et al., 2004). Turbulent flows of the fluid metallic inner core of earth mainly contribute to GMF and the effect of external MFs located in the ionosphere and the magnetosphere is very meagre (Qamili et al., 2013). As GMF extends beyond the earth’s surface it is this force along with magnetosphere that protects the earth and its biosphere, from the solar wind by deflecting most of its charged particles (Occhipinti et al., 2014).

Introduction Clean and renewable energy is a basic requirement for developmental activities. Global energy crisis is caused by increasing world population, escalating demand due to urbanisation, and continued dependence on fossil-based fuels. Non-renewable energy sources like coal, natural gas oil contribute 79 per cent of world electricity generation; only 21 per cent comes from renewable energy sources. Promoting the use of existing renewable energy sources and identifying new environment-friendly technology is gaining importance. Switching to renewable energy sources like wind energy, ocean energy and solar energy is gaining a lot of importance. These green technologies emit less greenhouse gases into the atmosphere and hence are pollution free and immensely available. Recently, investigators have identified plants as weak energy sources. Plants are versatile organisms capable of communicating with each other with a number of signaling mechanisms. It was observed that plants generate electronic signals inside their system. The concept of utilising electronic signals for studying various physiological plant processes was first put forth by Sir Acharya J. C. Bose, an eminent biophysicist, botanist, archaeologist and polymath from India (Fromm and Lautner, 2007). His ideologies and concepts of movements of plants laid the foundation for modern electrophysiology-a branch of physiology that deals with electrical phenomena associated with metabolic functions. Attempts have been made to harvest electricity from free electrons available in plant leaves produced during photosynthesis and from rhizosphere of plants formed as a result of bacterial activity. Currently, a lot of attention is being given to improvise and develop this technology. To proceed forward in this direction, it is very critical to understand the mechanism of electrical signaling in plants.

Introduction Plant architecture is defined as a three-dimensional organization of plant body in terms of its size, shape position of leaves, flower organs and branching pattern. Earlier this was the only criterion for systematic and taxonomic classification of plant species and the best means of identifying them (Stecconi, 2006). Study of plant architecture emerged as a new scientific discipline some 30 years ago. The subject derives its base from earlier works on plant morphology (Halle and Oldeman, 1970) but currently it is integrated with several disciplines of plant sciences ecology and engineering. Modification in plant architecture causes alteration in primary and secondary growth. This occurs due to differences in phyllotactic arrangement, branching pattern and floral differentiation. Plant architecture can be modulated by various parameters like climate, agronomic practices and human interventions. Manipulation of plant architecture is a major area in plant science which is currently adopted for productivity improvement by breeders, agronomists, horticulturists and landscape managers. However, the basis for such manipulation lies in the knowledge of the basic architecture of plants and its significance.

Introduction Plants are considered as immobile organisms with poor sensitivity and limited ability to respond. Within the plant kingdom, Mimosa pudica (also called the sensitive plant), Drosera (sundews), Dionea muscipula (flytraps) and tendrils of climbing plants which showed rapid and purposeful movements were considered as exceptions. These sensitive plants attracted attention of outstanding pioneer researchers like Pfeffer (1845-1920), Burdon-Sanderson (1828-1905), Darwin (1809-1882), Haberlandt (1854-1945) and Bose (1858-1937). Stahlberg, 2006 reported the presence of various mechanoreceptors in such species which could trigger action potentials (APs) which activated these sudden movements. The first extracellular recording of a plant action potential (AP) development was initiated by Charles Darwin; later, the animal physiologist Burdon-Sanderson in 1873 performed similar studies on leaves of the Venus flytrap (Dionea muscipula Ellis). Haberlandt (1884) demonstrated that phloem strands were the actual paths for excitation by destroying the external, non-woody part of vascular bundles. This notion was confirmed in Mimosa and other plant species by a number of recent studies. Houwink (1935) carried out experiments with two species of Vitis (grape) and obtained electrical fluctuations which was similar and comparable with the action potentials he obtained with Mimosa. In 1907, Bose, used a D’arsonval galvanometer to demonstrate propagating electrical effects in different genera of plants such as Ficus, Artocarpus, Cucurbita, Corchorus, “fern” etc. APs have their largest amplitude in phloem sieve cells and cells adjacent to this area (Sibaoka, 1969). Other studies found that AP-like signals are propagated with equal rate and amplitude throughout the cells of vascular bundles.