As plant science is a broad and diverse field, we provide brief explanations of the background, context and prospects for addressing each question with the aim of making the questions accessible to the broadest possible audience.

There is no ideal way to divide the questions into topic areas. Many questions inevitably and desirably span more than one category, and some particularly substantial topics merit multiple questions. For the purposes of this paper, the panel decided to categorize the questions into five broad areas that reflect the breadth and depth of plant research discussed during the 2‐d workshop: Society, Environment and adaptation, Species interactions, Understanding and utilizing plant cells, and Diversity.

A. Society

Here we consider the overall significance of plants and plant science to human society in general. We open with 10 questions that the panel felt encapsulated the most burning societal issues that should be addressed by plant science, followed by other societal questions selected by the panel. More specific biological questions in plant science follow in later sections.

The 10 questions most important to society

A1. How do we feed our children’s children?

By 2050 the world population will have reached c. 9 billion people. This will represent a tripling of the world population within the average lifetime of a single human being. The population is not only expanding, but also becoming more discerning, with greater demands for energy‐intensive foods such as meat and dairy. Meeting these increasing food demands over the years to come requires a doubling of food production from existing levels. How are we going to achieve this? Through the cultivation of land currently covered in rainforests, through enhanced production from existing arable land or by changing people’s habits to change food consumption patterns and reduce food waste? The reality is probably a combination of all three. However, if we are to reduce the impact of food production on the remaining wilderness areas of the planet then we need significant investment in agricultural science and innovation to ensure maximum productivity on existing arable land.

A2. Which crops must be grown and which sacrificed, to feed the billions?

The majority of agricultural land is used to cultivate the staple food crops wheat (Triticum aestivum), maize (Zea mays) and rice (Oryza sativa), the oil‐rich crops soy (Glycine max), canola (Brassica napus), sunflower (Helianthus spp.) and oil palm (Elaeis guineensis) and commodity crops such as cotton (Gossypium spp.), tea (Camellia sinensis) and coffee (Coffea spp.). As the world population expands and meat consumption increases, there is a growing demand for staples and oil‐rich crops for both human needs and animal feed. Without significant improvements in yields of these basic crop plants, we will experience a squeeze on agricultural land. It is therefore essential that we address the yield gap; the difference between future yield requirements and yields available with current technologies, management and gene pools. Otherwise we may be forced to choose between production of staple food crops to feed the world population and the production of luxury crops, such as tea, coffee, cocoa (Theobroma cacao), cotton, fruits and vegetables.

A3. When and how can we simultaneously deliver increased yields and reduce the environmental impact of agriculture?

The first green revolution of the late 1950s and early 1960s generated unprecedented growth in food production. However, these achievements have come at some cost to the environment, and they will not keep pace with future growth in the world population. We need creative and energetic plant breeding programmes for the major crops world‐wide, with a strong public sector component. We need to explore all options for better agronomic practice, including better soil management and smarter intercropping, especially in the tropics. Finally, we need to be able to deploy existing methods of genetic modification that reduce losses to pests, disease and weeds, improve the efficiency of fertilizer use and increase drought tolerance. We also need to devise methods to improve photosynthetic efficiency, and move the capacity for nitrogen fixation from legumes to other crops. These are all desirable and, with public support, feasible goals.

A4. What are the best ways to control invasive species including plants, pests and pathogens?

Invasive species are an increasingly significant threat to our environment, economy, health and well‐being. Most are nonindigenous (evolved elsewhere and accidentally introduced) and have been removed from the constraints regulating growth in their native habitat. The best method of control is to prevent establishment in the first place or to quickly identify establishment and adopt an eradication programme. However, if an invasive species becomes established many of the options for removal can cause environmental damage, for example chemical control or mechanical excavation. Biological control (introduction of a natural predator/pathogen) can work well as long as the control organism targets only the invasive species. Otherwise there is a risk that the control organism might also become an invasive species. Alternatives, such as manipulating existing natural enemies and/or the environment to enhance biological control, are also being developed. Sustainable solutions are required if we are to deal with the continually growing problem of invasive species.

A5. Considering two plants obtained for the same trait, one by genetic modification and one by traditional plant breeding techniques, are there differences between those two plants that justify special regulation?

The products of traditional plant breeding are subject to no special regulations, even though the wild sources of germplasm often used by breeders may contain new components that have not been assessed before. A plant derived by genetic modification, however, is highly regulated, even though the target genotype and the modification itself may both be highly characterized and accepted as innocuous for their intended use. This is a major exception to the norm for safety regulation in food and other areas, which is normally based on the properties of the object being regulated. It is important for food safety and for the public’s perception of science and technology in general to establish whether there are any objective differences between these groups of products that justify the different approaches to their regulation.

A6. How can plants contribute to solving the energy crisis and ameliorating global warming?

Plants use solar energy to power the conversion of CO 2 into plant materials such as starch and cell walls. Plant material can be burnt or fermented to release heat energy or make fuels such as ethanol or diesel. There is interest in using algae (unicellular aquatic plants) to capture CO 2 emissions from power stations at source. Biomass cellulose crops such as Miscanthus × giganteus (Poaceae) are already being burnt with coal at power stations. There is understandable distaste for using food crops such as wheat and maize for fuel, but currently 30% of the US maize crop is used for ethanol production, and sustainable solutions are being found. Sugarcane (Saccharum officinarum) significantly reduces Brazil’s imports of fossil fuels. Agave (Agavea fourcroydes) in hot arid regions can provide very high yields (> 30 T ha−1) of dry matter with low water inputs compared with other crops. To ameliorate global warming, CO 2 must be taken out of the air and not put back. There is considerable interest in ‘biochar’ in which plant material is heated without air to convert the carbon into charcoal. In this form, carbon cannot readily re‐enter the air, and, if added to the soil, can increase fertility. Carbon markets do not currently provide sufficient incentive for farmers to grow crops simply to take CO 2 out of the air.

A7. How do plants contribute to the ecosystem services upon which humanity depends?

Ecosystem services are those benefits we human beings derive from nature. They can be loosely divided into supporting (e.g. primary production and soil formation), provisioning (e.g. food, fibre and fuel), regulating (e.g. climate regulation and disease regulation) and cultural (e.g. aesthetic and recreational) services. Plants are largely responsible for primary production and therefore are critical for maintaining human well‐being, but they also contribute in many other ways. The Earth receives virtually no external inputs apart from sunlight, and the regenerative processes of biological and geochemical recycling of matter are essential for life to be sustained. Plants drive much of the recycling of carbon, nitrogen, water, oxygen, and much more. They are the source of virtually all the oxygen in the atmosphere, and they are also responsible for at least half of carbon cycling (hundreds of billions of metric tons per year). The efficiency with which plants take up major nutrients, such as nitrogen and phosphorus, has major impacts on agricultural production, but the application of excess fertilizers causes eutrophication, which devastates acquatic ecosystems. Plants are already recognized as important for sustainable development (e.g. plants for clean water) but there are many other ways that plants might contribute. A combined approach of understanding both the services provided by ecosystems and how plants contribute to the functioning of such ecosystems will require interdisciplinary collaboration between plant scientists, biogeochemists, and ecologists.

A8. What new scientific approaches will be central to plant biology in the 21st Century?

Biologists now have a good general understanding of the principles of cell and developmental biology and genetics, and how plants function, change, and adapt to their environment. Addressing the questions in this list, including those related to generating crops that can deal with future challenges, will require detailed knowledge of many more processes and species. New high‐throughput technologies for analysing genomes, phenotypes, protein complements, and the biochemical composition of cells can provide us with more detailed information in a week than has ever been available before about a particular process, organism or individual. This is delivering a deluge of information that is both exhilarating and daunting. The challenge is to develop robust ways of analysing and interpreting this mountain of data to answer questions and deliver new insights. The skill sets required to make full use of the new information extend far beyond those previously expected from biologists. There is general agreement that we need a new era of collaboration between all types of plant scientists, geographers, geologists, statisticians, mathematicians, engineers, computer scientists, and other biologists to evaluate complex data, find new relationships, develop and test hypotheses, and make discoveries. Challenges include understanding complex traits and interactions with the environment, generating ‘designer crops’, and using modelling to predict how different genotypes will cope with alterations in the climate.

A9. (a) How do we ensure that society appreciates the full importance of plants?

Plants are fundamental to all life on Earth. They provide us with food, fuel, fibre, industrial feedstocks, and medicines. They render our atmosphere breathable. They buffer us against extremes of weather and provide food and shelter for much of the life on our planet. However, we take plants and the benefits they confer for granted. Given their importance, should we not pay plants greater attention and give higher priority to improving our understanding of them? Awareness could be increased through the media, school education, and public understanding of science activities, but a major step‐change in activity will be required to make a substantial difference.

A9. (b) How can we attract the best young minds to plant science so that they can address Grand Challengesfacing humanity such as climate change, food security, and fossil fuel replacement?

Everyone knows that we need doctors, and the idea that our best and brightest should go into medicine is embedded in our culture. However, even more important than medical care is the ability to survive from day to day; this requires food, shelter, clothes, and energy, all of which depend on plants. Beyond these essentials, plants are the source of many other important products. As is clear from the other questions on this list, plant scientists are tackling many of the most important challenges facing humanity in the 21st Century, including climate change, food security, and fossil fuel replacement. Making the best possible progress will require exceptional people. We need to radically change our culture so that ‘plant scientist’ (or, if we can rehabilitate the term, ‘botanist’) can join ‘doctor’, ‘vet’ and ‘lawyer’ in the list of top professions to which our most capable young people aspire.

A10. How do we ensure that sound science informs policy decisions?

It is important that policy decisions that can affect us all, for example environmental protection legislation, are based on robust and objective evidence underpinned by sound science. Without this, the risk of unintended consequences is severe. Ongoing dialogue between policy makers and scientists is therefore critical. How do we initiate and sustain this dialogue? How do we ensure that policy makers and scientists are able to communicate effectively? What new mechanisms are needed to enable scientists to respond to the needs of policy makers and vice versa?

The Supporting Information, Notes S1, provides explanatory text for the remaining questions.