INTRODUCTION

Plants produce a bewildering array of exotic chemicals: the pigments which give color to leaves, petals, fruits, and seeds; the substances that create aromas and tastes; those formed to help defend against attack by diseases, predators, and competitors; and others with no known function (Figure 11).

We take advantage of the munificence of plants as chemical factories in many different ways, most crucially in medicine. Worldwide, at least a quarter of medicines come directly from plants; in some places, much more.

SIGNALING

Plants and animals put a great deal of time and energy into attracting attention to themselves. By way of colors, scents, sounds, vibrations, and elaborate movements, such as those in mating displays, living things send signals to one another. The distances over which these signals are sent may be short (a few centimeters) or long (kilometers in the case of some chemical sex attractants; the male gypsy moth can detect the scent put out by a female over 3 km away!).

Signaling is one of the essentials of life. No plant or animal could afford the cost of giving off “pointless” signals; the energy cost is too great. In The Origin of Species, Charles Darwin put it as well as anyone could in the case of flower color:

Introduction

There is little doubt that climate change elicits change in plant communities. These changes are conspicuous in those plant associations that lie in the marginal zone of their ranges. The lowland Sphagnum dominated mires are frequent in cool and humid climates (e.g., in north and west Europe), but are very rare under continental climatic conditions. Three of the five studied areas are the southernmost occurrences of the Oxycocco-Sphagnatea associations on the plains of Europe (Simon 1992a). Their formation and development are caused by edaphic conditions. They were formerly known as “ice age relict” associations. However, current paleobotanical research has documented that these peat moss dominated habitats are much younger (Jakab & Magyari 2000; Magyari 2002). They are extremely sensitive to changes in their environment (which are under marked human influence). These ecosystems are the most sparse and diverse mires of Hungary. All of them are strictly protected. The quality of these peat moss dominated habitats has deteriorated over the past 50 years owing to human and natural influences, and so the Directorate of Hortobágy National Park began their restoration. Restoration measures include the following: blocking of drainage canals; planting of gallery oak forests; initiating artificial water replenishment; and the prohibition of chemical usage on the arable lands around the mires. The aim was to restore these unique habitats so as to provide better conditions for peat mosses to propagate. During the drying period we were able to follow the degradation of the peat moss carpet under a willow carr.

INTRODUCTION

Plants are exposed to unusual, even extreme, environmental conditions, daily, seasonally, or from time to time depending on where they live. Beneath the benign face of the natural green world, plants are waging battles constantly against difficulties posed by their environments. Because these stresses often lead to reduced health in plants, just as they do in animals, they are also of considerable interest to agricultural scientists. Stressed crops usually produce lower yields. Understanding how plants cope with and respond to environmental stresses (often called abiotic stresses to distinguish them from those caused by diseases and predators, which are biotic stresses) is, therefore, important to breeders whose job it is to develop crop varieties with resistance to stresses while maintaining high yields.

WHAT IS STRESS?

The word stress was used first by engineers to explain what happens when a force is applied to an object; strain is the change in the object caused by the stress. For example, an elastic band can be stressed by forcing it to expand; strain is how much the band is stretched by the force applied. Stresses and strains in the physical world can often be precisely applied and measured.

DEFINING “BIOLOGICAL” STRESS AND STRAIN

In a cultivated context

Anything that does not allow a plant to reach its full potential is a stress which will have a consequent strain, such as lower growth or seed production.

INTRODUCTION

The fastest growing trees are the eucalypts, one type of which, found in New Guinea, has been known to add nearly 8 m to its height in 1 year. Even these “sprinters” are eclipsed by giant bamboo, which can grow over 1 metre a day, 30 m in under 3 months.

At the other extreme, a Sitka spruce found at the tree limit in the Arctic had one of the slowest growth rates on record. From measurements of the annual growth rings in the trunk it was estimated to be about 100 years old yet was only 28 cm tall.

The total growth of which some plants are capable in a lifetime is startling. One of the largest giant redwood trees found had a wood volume of more than 1500 m3 and weighed over 1000 tonnes. Since the seed of the giant redwood weighs less than 0.005 g, the weight increase over the lifetime of this specimen was more than 250 billion times. Large trees like these can live for more than 4000 years, illustrating that plants often combine in their bodies tissues of great antiquity with others that are still youthful, producing new leaves, shoots, roots, fruits, and seeds.

CONTROL OF DEVELOPMENT AND GROWTH FORM

In animals, organs develop very early in life and become an integral part of the whole organism without which it cannot function.

The idea for this book arose from a conversation I had one day with two of my neighbors. Neither is a plant specialist but both are keen gardeners. One has in his garden a number of large trees of which not everyone is an unqualified admirer, including the other neighbor. For one thing, the trees shade adjacent gardens from direct sunlight for much of the day, including that of the second neighbor, a somewhat sensitive matter at this northerly latitude where there is a relatively short growing season. In the autumn, immense numbers of leaves find their way into the general neighborhood, often late in the season since some of these particular trees continue shedding leaves even after the first snow. The task of cleaning up frozen, congealed, decaying leaves is not universally appreciated.

Not for the first time, then, the owner of one of the shaded gardens was trying to persuade the tree-loving neighbor to remove his trees which, to the former, were obstacles to productive gardening. As the conversation developed, it became obvious that the aggrieved party thought the main bulk of a tree came from the soil since he made repeated reference to the fact that the offending trees were taking in significant quantities of nutrients through their roots. Of course, plants do absorb many essential minerals and water from soil but we have known for a long time, for more than 200 years in fact, that air, not soil, is the source of the main building block (carbon) from which the bulk of green plants is manufactured.

Tundra vegetation in the changing climate

In the 1990s global warming was envisioned scientifically as being highly influential and pronounced at high latitudes (Mitchell et al. 1990; Maxwell 1992). Since then, impacts of climate change have been confirmed, especially in the indisputable data of increased air surface temperatures in both the Alaskan Arctic and Europe (Overpeck et al. 1997; Keyser et al. 2000; Serreze et al. 2000; EEA 2004). Ostensibly, climate change is currently affecting life in the world's ecosystems with intensified ramifications of escalating temperatures (IPCC 2007). The Arctic has had a rapid increase in mean temperatures over the past few decades, twice the rate of the rest of the world (ACIA 2005). Its warmest year ever recorded was in 2007 (Richter-Menge et al. 2008). Biomes already seem to be changing owing to climate differences, indicated by observations of enhanced plant growth at high northern latitudes (Myneni et al. 1997) and mid-latitudes (Nemani et al. 2003), landscape-level shifts in species ranges, decline in species populations (McCarthy et al. 2001), and changes in species diversity (EEA 2004). Continuing Arctic climate change will therefore have the effect of encouraging forest expansion into tundra biomes, and the tundra vegetation as we know it will greatly change, shifting in its extent, distribution, and species composition. These changes will probably be unprecedented compared with those of past millennia.

Introduction

Ultraviolet radiation (UVR) has many effects on photosynthetic organisms. It is a minority component (about 6%) of solar radiation in comparison with the dominant visible/photosynthetic and infrared bands. However, UVR is a natural environmental factor that has been involved in the appearance of diverse adaptive changes in organisms through the development of life on Earth (Cockell & Knowland 1999). UVR induces a number of biological processes in all living organisms, including humans, and many of them are harmful. In this respect, among the three wavelength categories into which UVR is divided by the CIE (Commission Internationale d'Eclairage), the most damaging UV-C (< 280 nm) is not relevant at the present time because of its complete absorption by stratospheric oxygen and ozone, but both UV-B (280–315 nm) and UV-A (315–400 nm) penetrate the biosphere and have significant biological effects. These effects are highly dependent on wavelength, and different biological weighting functions have been conceived to calculate the biologically effective UV (UVBE). UVBE encompasses UV-A and UV-B. However, given the logarithmic increase in effectiveness with decreasing wavelength, UVBE is dominated by UV-B, especially at shorter wavelengths. Therefore, most studies on the effects of UVR have dealt with UV-B. This has been especially true since the discovery of the anthropogenic stratospheric ozone reduction, because UV-B (and not UV-A) is absorbed by stratospheric ozone, and thus ozone reduction leads to an increase in surface UV-B levels.

This book is dedicated to Zoltán Tuba. Its origin was a symposium entitled Ecological Responses of Bryophytes to Changing Climate. It was presented at the American Bryological and Lichenological Society (ABLS) meeting with the Botanical Society of America (BSA) in Chico, California, in 2006. Nancy Slack, then president of ABLS, and Zoltán Tuba of Gödöllő University, Hungary, organized the symposium, which included speakers from many different countries. An editor at Cambridge University Press (England) saw the program on the Internet and asked the organizers to write a book on this subject. All the symposium speakers agreed to contribute chapters; subsequently, others doing important work in this field were asked to join them. Zoltán Tuba worked on the book with Nancy Slack from 2006 until shortly before his untimely death at 58 in July 2009. In the fall of 2009 Lloyd R. Stark, an active researcher in this field and co-author of two of the chapters, agreed to work with Nancy Slack to finish the book. Zoltán was a major contributor to research in ecophysiology of bryophytes in relation to climate change, as well as in other fields. He will be greatly missed as a scientist as well as a friend and co-worker.

A number of people have written to the present editors about Zoltán. In addition, part of an obituary by Zoltán's mentor, Professor Gábor Fekete: In Memoriam Zoltán Tuba (1951–2009), in Acta Botanica Hungarica vol. 52/1–2 (2010), is quoted here:

INTRODUCTION

In preparation for the most unfavorable weather, a plant may need special protection against the climate. These periods of recurring poor growing conditions must be anticipated well in advance. It would be no use for the plant to begin preparing for winter, for example, the morning of the first frost or for a long, dry, hot season in a desert when water was no longer available.

What a plant does in preparation for long periods of poor weather is often quite elaborate, requiring a long period of good weather after the signal is received that an unfavorable season is approaching. The signal received by the plant cannot be linked directly to future poor conditions. For example, it is not low temperature which triggers the processes inside a plant leading to preparations for winter. Preparations might begin in mid to late summer when the temperature is still high. Shortening day length is a more reliable signal than temperature for plants to use to anticipate winter.

SURVIVAL STRATEGIES

Winter buds

When forming winter buds a plant stops producing new leaves. Instead, small, tough scales are formed which tightly enclose the soft, delicate growing points in terminal buds on branches. They can withstand freezing and thawing many times over without disintegrating and they repel water while keeping the tender tissues inside moist and alive. Only in the spring, when their task is complete, are they shed as the growing points begin once more to grow.

Introduction

The climate of Europe has changed in the past century. An increase in mean annual air temperature of +0.90°C could be observed between 1901 and 2005 (Jones & Moberg 2003). For the period 1977–2000, trends are even higher for Europe's mountain regions (Böhm et al. 2001). Beniston (2005) showed that for the alpine region minimum temperatures have increased up to 2 °C during the twentieth century, whereas the snow cover period has been reduced (IPCC 2007). The alpine and nival (uppermost altitudinal zone of the Alps above the closed alpine grassland) zones (e.g., Grabherr 1997) of high mountain ecosystems are considered to be particularly sensitive to warming (Diaz & Bradley 1997; Haeberli & Beniston 1998) as these ecosystems are determined by low temperature conditions. This life zone offers ideal conditions to study climate change effects because (1) direct human impact is very low, (2) its ecological systems are comparatively simple, at least in the upper elevation levels, and (3) its systems are dominated by abiotic, climate-related ecological factors. The importance of biotic factors such as competition decreases with altitude (Körner 1994; Callaway et al. 2002). Since high mountain plants have proven to respond sensitively to climate change (Grabherr et al. 1994, 2001), great efforts were made to establish the large-scale monitoring network GLORIA (Global Observation Research Initiative in Alpine environments) (Pauli et al. 2003).

INTRODUCTION

An impressive achievement in biology in the twentieth century was gaining a comprehensive understanding of respiration. All living things respire. Still, the knowledge that most people have of what is involved often begins and ends with: “we inhale air rich in oxygen and exhale it enriched with carbon dioxide.” But there is much more to it than that.

The foods we eat are slowly burned or “combusted,” as Lavoisier described it more than 250 years ago (see Chapter 1). Using the O2 from the air, we slowly convert carbohydrates, fats, proteins, and other substances, finally, to CO2 and water. This releases the energy contained in foods, some of it in the form of chemical energy, which is useful to us; the rest is given off to our surroundings as heat. We put the useful energy to work to sustain our life support systems – to drive our muscles and other organs, keep us warm, feed our brains, and build our complex molecules (Figure 2).

PLANTS NEED RESPIRATION AS WELL AS PHOTOSYNTHESIS

We might suppose that because plants have access to an endless supply of energy from the sun they do not need any other source – not so. Not all parts of a plant photosynthesize, only those that are green; however, non-green parts also need energy. In addition, photosynthesis occurs only during the day but plants grow round the clock.

Introduction

Attention to climate change has significantly increased in the past 20 years, both on global and on regional scales. A great deal of research has been carried out relative to global warming based on alteration of species distributions. Examples are a study supported by a large number of African vascular plant species (McClean et al. 2005), another using amphibian and reptile distribution (Araújo et al. 2006), and also, on a European scale, diadromous fish distribution (Lassalle et al. 2008). In a more narrow range, we can cite research using alpine plants in the Swiss Alps (Guisan & Theurillat 2000), on the effects on rare lichens in the UK (Binder & Ellis 2008), or identifying the dynamic in snowbed bryophytes related to the duration of snow-lie in Scotland (Woolgrove & Woodin 1994).

Bryophytes are important ecologically; they constitute an important component of biodiversity and are recognized as keystone species of ecosystem monitoring. Many bryophyte species have been adversely affected by human activities, principally because of deterioration in essential habitats (Bates & Farmer 1992) or water quality (Vanderpoorten & Klein 1999), as well as increased nitrate (Lee et al. 1998) and air pollution (Zechmeister et al. 2007). These adverse effects have been widely cited as to why some bryophytes are now considered endangered.

Bryophyte species have, in general, tolerance to wide ranges of temperature. This attribute is largely due to their water relations, since they can survive better at higher temperature extremes when dry than when wet.

Attempts in the past to create genetically engineered (GE) crops have led to a great deal of negative publicity about and considerable public antipathy towards the technology; this is unfortunate. Improvements to the technology have moved well beyond the first generation of GE crops, those with resistance to herbicides. More recent advances in this field have considerable relevance to several topics covered here in Parts IV and V; further advances now in the early stages of exploration and exploitation promise to transform the world as we know it.

One major driver in the future of GE agriculture will be climate change. The number one tool that all living organisms use to respond to alterations to their environment which occur naturally over time is genetic change, which is adaptive. But the kind of genetic change dependent on simple mutations of existing endogenous genes will not bring about adaptation fast enough to meet the challenges posed by rapid climate change in the case of crop species. GE is the only technology that is both sufficiently rapid and targeted to bring about adaptation to and mitigation of the human forcing of changes to global and regional environments in crops.

For example, nitrous oxide, a greenhouse gas some 300 times more harmful than CO2, is percolating into the atmosphere from soil, to which we are adding increasing amounts of nitrogen fertilizer, worldwide.

INTRODUCTION

Increasingly, people are thinking about and acting on what they include in their diets. There is a constant bombardment from health specialists, through the media and the internet, exhorting us to maintain a balance in what we eat, an important component of a well regulated lifestyle. Increasingly, we are learning that to eat immoderately and injudiciously is harmful.

We are also generally aware that plants become sick, just as animals do, when not supplied with the nutrients needed for good health. For animals, these requirements are elaborate and include the balanced provision of complex molecules in their diets, such as carbohydrates, fats, and proteins, as well as vitamins and certain minerals. Plants are different in being able to produce their own organic molecules from simpler, inorganic ones.

But, in common with animals, plants need certain minerals for healthy growth. Some of these are essential to both plants and animals in greater or lesser amounts; others are essential either to animals or plants but not both; and some are of probable, but at present uncertain, value to either.

ESSENTIAL MINERAL ELEMENTS

We eat some plant materials for their mineral content, like bananas for their potassium and spinach for its iron, nutrients which are essential both to animals and plants. Sodium is essential to animals but is required for only C4 plants. Molybdenum is essential to plants but is toxic to animals when more than a trace is present in food.