method, diagnosis, or treatment by physicians for any particular patient. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging‐in‐Publication Data
Names: Cobb, Andrew, author.
Title: Herbicides and plant physiology / Professor Dr Andrew H. Cobb, formerly Emeritus Professor of Plant Science, Dean of Academic Affairs and Director of Research at Harper Adams University, Shropshire, UK.
Description: Third edition. | Hoboken, NJ : Wiley‐Blackwell, [2021] | Includes bibliographical references and index.
Identifiers: LCCN 2021031562 (print) | LCCN 2021031563 (ebook) | ISBN 9781119157694 (paperback) | ISBN 9781119157717 (adobe pdf) | ISBN 9781119157700 (epub)
Subjects: LCSH: Plants–Effect of herbicides on. | Plant physiology. | Herbicides–Physiological effect. | Weeds–Control.
Classification: LCC SB951.4 .C63 2021 (print) | LCC SB951.4 (ebook) | DDC 632/.954–dc23
LC record available at https://lccn.loc.gov/2021031562 LC ebook record available at https://lccn.loc.gov/2021031563
Cover Design: Wiley
Cover Image: courtesy of Dr J P H Reade
Preface
He who has bread may have many troubles; he who lacks it has only one.
(Byzantine proverb)
A peasant must stand for a long time on a hillside with his mouth open before a roast duck flies in.
(Chinese proverb)
The origin of the word herbicide is a combination of the Latin words herba (noun, herbaceous plant) and caedere (verb, to kill; R.L. Zimdhal, Weed Science17, 137–139, (1969).
It is now 30 years since the first edition of this book was published and so it is timely to reflect on herbicide use and the environmental consequences of their use. While we now have fewer products in our agrochemical armoury, farmers and growers have become dependent on fewer active ingredients, and glyphosate dominates the global market. This third edition aims to update the reader on how herbicides contribute to modern agriculture, how they are discovered and developed, and how they interact with plant growth and development and the environment. Since the publication of the second edition in 2010 there have been many advances in our understanding of plant physiology, especially regarding how plants function in tune with their ever‐changing environment and how post‐translational modifications provide regulatory control of most plant processes. Modern agriculture, however, still faces many challenges.
1 The global food challenge. To some, the continuing expansion of the human population will inevitably outstrip the growth of our food supply, resulting in global starvation. To others, an expansion of arable land, a growing global food trade and the increases in crop yield predict a more optimistic future. Yet is it inevitable that a growing food supply will continue to meet demand?
2 The problem. More than half the global population will suffer some form of malnutrition by 2030 unless urgent action is taken to increase access to food of high nutritional quality. The Food and Agriculture Organization of the United Nations (FAO et al., 2017) estimated that 815 million persons were hungry in 2016 (11% of the global population), an increase of 35 million since 2015. While 155 million children have stunted growth owing to poor nutrition, 2 billion persons suffer from hunger, while 1.9 billion adults and 41 million children are either overweight or obese. In addition, the human population is expected to grow by about 80 million per annum to an estimated 10 billion in 2050 (Oerke and Dehne, 2004). Furthermore, the global impact of the current covid‐19 pandemic could result in at least a further 200 million undernourished persons. How can we expect to produce 70% more food to feed them all?
3 Food security. Food security is an increasing global problem in the face of climate change, combined with increasing populations and volatile food prices. With the global population growing at 230,000 persons each day and 60% of us now living in cities, the pressure on farmers to increase crop yields is ever present. At the same time, in the UK as an example, the land available per head of population has decreased from 0.8 to 0.2 hectares in the last 50 years. Every year 12 million hectares is degraded globally owing to drought, de‐forestation and desertification, an area roughly the size of Nicaragua, the largest country in Central America. Furthermore, global freshwater supply is becoming increasingly limited and unreliable to an estimated 700,000 persons, notwithstanding the fluctuations in weather as a result of climate change. We are experiencing greater extremes of weather, such as flooding or drought, and so we need to use the available fresh‐ and artesian‐water more wisely. This is especially so whether we grow crops or raise animals. For example, it is estimated that 70 litres of water are needed to produce one apple, whereas 15,000 litres are needed for one kg of beefsteak! It is interesting to note that the carbon footprint of beef and lamb is three times that of pork, five times that of chicken, over 30 times that of bread wheat and 50 times that of potatoes. Urbanisation and increasing incomes generate a higher demand for animal protein, yet beef production requires four times more land than dairy, per unit of protein consumed. In addition, beef is seven times more resource intensive than pork and poultry, and 20 times more so than pulses. Not forgetting that animal production results in increased greenhouse gas emissions. It is a further uncomfortable fact that about a third of all food produced never reaches the table. This value is higher for fruit and vegetables, and such losses are even higher in the developing world, owing to the lack of effective storage and/or transport (IFPRI, 2016).As available land for farming is in ever shorter supply and extremes in climate become more evident, many scientists predict an increased degradation of soils and a need for increased attention to land management. In recent years in the UK, for example, farmers have seen above average rainfall with increasing soil erosion, degradation and run‐off. Palmer and Smith (2013) noted that 75% of fields planted with maize or potatoes in the south‐west of England were severely damaged by soil degradation, with one in five sites experiencing serious rill and gully erosion. Some 60% of fields growing winter cereal crops,
