This book addresses the question of why there are so many leaves on Earth and why living foliage resists attack by all but the most specialized organisms. This is of broad interest in biology given the importance of leaves in terrestrial ecosystems and since plants form the basis of the carbon cycle. Part of the reason that leaves are resilient and resist attack is that they are well defended. However, although some leaf defences are easily seen, most defence mechanisms operating at the level of cells and molecules are invisible to the naked eye. Perspectives from both the laboratory and the f ... More

This book addresses the question of why there are so many leaves on Earth and why living foliage resists attack by all but the most specialized organisms. This is of broad interest in biology given the importance of leaves in terrestrial ecosystems and since plants form the basis of the carbon cycle. Part of the reason that leaves are resilient and resist attack is that they are well defended. However, although some leaf defences are easily seen, most defence mechanisms operating at the level of cells and molecules are invisible to the naked eye. Perspectives from both the laboratory and the field are combined throughout the book, which begins by examining the global scale of herbivory. The book then discusses the direct physical and chemical defences both on leaf surfaces and in the leaf interior and emphasizes how plants use specialized defence cells. Leaf survival also depends on various indirect defences conferred by carnivorous organisms that are attracted by plants that are under attack by herbivores. Remarkably, both direct and indirect defence processes are controlled and co-ordinated, and the molecular mechanisms that underlie this are now emerging. Recently discovered roles of the jasmonate signal pathway in regulating direct and indirect defences and plant growth are discussed. A central feature of the book is its emphasis on the co-evolution of leaf defences and the digestive tracts of animals including humans. This underscores the importance of understanding the impact of plant defences in agriculture, much of which depends on protecting leaves from pests.