Green plants work as a 'natural pollutant sink' on earth intercepting dust and pollutants from air and water. During photosynthesis, plants absorb CO2 and simultaneously other gases like oxides of sulphur & nitrogen (SO2 & NOx), ozone (O) and airborne ammonia (NH3) through their stomata. Plants also reduce air pollution by intercepting suspended particulate matters (SPM) and aerosols and retaining them on the leaf surface. Trees take up more pollutants including the particulate pollutants (PM10), than shorter vegetation. This book presents new and significant research in the role of plants in protecting the environment.