Root Methods

A comprehensive review of all modern methods for plant root research, both in the field and in the laboratory. It covers the effects of environmental interactions with root growth and function, focussing in particular on the assessment of root distribution and dynamics. It also describes and discusses the processing of root observations, analysis and modelling of root growth and architecture, root-image analysis, computer-assisted tomography and magnetic resonance imaging. Furthermore, a survey of the application of isotope techniques in root physiology is given.

This book sets out to state computationally verifiable initial conditions for predicting the immediate appearance of the guaranteed and fast convergence of iterative root finding methods. Attention is paid to iterative methods for simultaneous determination of polynomial zeros in the spirit of Smale's point estimation theory, introduced in 1986. Some basic concepts and Smale's theory for Newton's method, together with its modifications and higher-order methods, are presented in the first two chapters. The remaining chapters contain the recent author's results on initial conditions guaranteing convergence of a wide class of iterative methods for solving algebraic equations. These conditions are of practical interest since they depend only on available data, the information of a function whose zeros are sought and initial approximations. The convergence approach presented can be applied in designing a package for the simultaneous approximation of polynomial zeros.

This book provides an excellent illustration of the interrelationship between progress in scientific methodology and conceptual advances, and its publica tion should contribute to further advances. It is well known that major advances in understanding often follow the development of new methods. The development of the acetylene reduction assay for nitrogenase activity provides a good example of this interrelationship between theory and methods. Theoretical knowledge led to a search for substrates for nitro genase that could be assayed for more easily than ammonium, the normal product of the enzyme. The discovery of the reduction of acetylene to ethylene by nitrogenase provided the ideal answer to the problem by provid ing a rapid, specific, nondestructive, and inexpensive assay for nitrogenase activity. This assay is now used by almost every laboratory doing research on nitrogen fixation. However, further use and development of the acetylene reduction assay has shown that it can underestimate nitrogenase activity and can even give incorrect relative values under some circumstances. The major problem is that exposure of legume nodules to acetylene can cause a large increase in the resistance to oxygen diffusion into the nodule. This reduced supply of oxygen decreases the rate of nitrogenase activity within a few minutes.

A comprehensive review of all modern methods for plant root research, both in the field and in the laboratory. It covers the effects of environmental interactions with root growth and function, focussing in particular on the assessment of root distribution and dynamics. It also describes and discusses the processing of root observations, analysis and modelling of root growth and architecture, root-image analysis, computer-assisted tomography and magnetic resonance imaging. Furthermore, a survey of the application of isotope techniques in root physiology is given.

The importance of rhizosphere in plant growth and development was first reported by Lorentz Hilter a century ago and it was redefined by Pinton as the zone that includes the soil influenced by the root along with root tissues colonized by microorganisms (Darrah, 1993). Roots are the major part of the plant through which plants derive nutrients and water from the soil. However, for higher efficiency of nutrient absorption and protection against abiotic and biotic stresses, plant roots establish sophisticated molecular signaling mechanisms with diverse soil flora and fauna. In the rhizosphere environment, the interaction between plant roots, soil and microbes occur in very complex ways and significantly effects on soil physical and chemical properties, which in turn modulate the microbial population in the rhizosphere (Nihorimbere et al., 2011). Recently, scientists have started realizing the importance of a specific rhizosphere interactions and its direct role in production of higher crop yield, while maintaining healthy soil conditions; which is the basis for sustainable agriculture and need of alternative approaches for overcoming some of the negative effects related to green-revolution, which includes overuse of chemical fertilizers, pesticides, reduced use of organic matter and poor nutrient management.

Root research under natural field conditions is still a step-child of science. The reason for this is primarily methodological. The known methods are tedious, time consuming, and the accuracy of their results is often not very great. Many research workers have been discouraged by doing such root studies. The need for more information on the development and distribution of plant roots in different soils under various ecological conditions is, however, obvious in many ecological disciplines. Especially the applied botanical sciences such as agriculture, horticulture, and forestry are interested in obtaining more data on plant roots in the soil. This book will give a survey of existing methods in ecological root research. Primarily field methods are presented; techniques for pot experiments are described only so far as they are important for solving ecological problems. Laboratory methods for studying root physiology are not covered in this book. Scientific publications on roots are scattered in many different journals published all over the world. By working through the international root literature I found that about ten thousand papers on root ecology have been published at the present. This is not very much compared with the immense literature on the aboveground parts of the plants, but is, however, too much to cite in this book.