82. Can we increase crop productivity without harming biodiversity 83. Can we define objective criteria to determine when and where intensive or extensive farming practices are appropriate? 84. How do plants contribute to ecosystem services? 85. How can we ensure the long-term availability of genetic diversity within socio-economically 86. How do specific genetic differences result in the diverse phenotypes of different plant species? That is, why is an oak tree an oak tree and a wheat plant a wheat plant? 87. Which genomes should we sequence and how can we best extract meaning from the 88. What is the significance of variation in genome size? 89. What is the molecular and cellular basis of plants' longevity and can plant life spans be 90. Why is the range of life spans in the plant kingdom so much greater than in animals? 91. What is a plant species? 92. Why are some clades of plants more species- rich than others? 93. What is the answer to Darwin s abominable mystery of the rapid rise and diversification of 94. How has polyploidy contributed to the evolutionary success of flowering plants? 95. What are the closest fossil relatives of the flowering plants? 96. How do we best conserve phylogenetic diversity in order to maintain evolutionary potential? Plant science is central to addressing many of the most important questions facing humanity Secure food production and quality remain key issues for the world in the 21st Century and the importance of plants extends well beyond agriculture and horticulture as we face declining fossil fuel reserves, climate change, and a need for more sustainable methods to produce fuel, fibre wood, and industrial feedstocks. There is also untapped potential in optimizing the nutritional properties of foods, and in identifying novel plant products such as medicines. Tackling these frontiers will require new scientific methods and collaborations as existing approaches are delivering incomplete answers Many of the most important questions that we have identified can only be addressed by the integrated efforts of scientists with diverse expertise. For example, many require close cooperation between scientists working to improve crops and those working on environmental stability and ecosystem services. Funding mechanisms, scientific publishing and conferences could be more effective in supporting and encouraging the efficient transfer of knowledge between different areas of plant science and this should be addressed In the longer term, changes to higher education may be required to ensure that future researchers have the most suitable background knowledge and skill sets to address the research challenges that they are likely to face New Phytologist(2011)192: 6-1282. Can we increase crop productivity without harming biodiversity? 83. Can we define objective criteria to determine when and where intensive or extensive farming practices are appropriate? 84. How do plants contribute to ecosystem services? 85. How can we ensure the long-term availability of genetic diversity within socio-economically valuable gene pools? 86. How do specific genetic differences result in the diverse phenotypes of different plant species? That is, why is an oak tree an oak tree and a wheat plant a wheat plant? 87. Which genomes should we sequence and how can we best extract meaning from the sequences? 88. What is the significance of variation in genome size? 89. What is the molecular and cellular basis of plants’ longevity and can plant life spans be manipulated? 90. Why is the range of life spans in the plant kingdom so much greater than in animals? 91. What is a plant species? 92. Why are some clades of plants more species-rich than others? 93. What is the answer to Darwin’s ‘abominable mystery’ of the rapid rise and diversification of angiosperms? 94. How has polyploidy contributed to the evolutionary success of flowering plants? 95. What are the closest fossil relatives of the flowering plants? 96. How do we best conserve phylogenetic diversity in order to maintain evolutionary potential? Plant science is central to addressing many of the most important questions facing humanity. Secure food production and quality remain key issues for the world in the 21st Century, and the importance of plants extends well beyond agriculture and horticulture as we face declining fossil fuel reserves, climate change, and a need for more sustainable methods to produce fuel, fibre, wood, and industrial feedstocks. There is also untapped potential in optimizing the nutritional properties of foods, and in identifying novel plant products such as medicines. Tackling these frontiers will require new scientific methods and collaborations as existing approaches are delivering incomplete answers. Many of the most important questions that we have identified can only be addressed by the integrated efforts of scientists with diverse expertise. For example, many require close cooperation between scientists working to improve crops and those working on environmental stability and ecosystem services. Funding mechanisms, scientific publishing and conferences could be more effective in supporting and encouraging the efficient transfer of knowledge between different areas of plant science and this should be addressed. In the longer term, changes to higher education may be required to ensure that future researchers have the most suitable background knowledge and skill sets to address the research challenges that they are likely to face. New Phytologist (2011) 192:6–12