The present edited book is an attempt to update the state of art of the knowledge on metabolism of ROS and antioxidants and their relationship in plant adaptation to abiotic stresses involving physiological, biochemical and molecular processes. The chapters are much focused on the current climate issues and how ROS metabolism can manipulate with antioxidant system to accelerate detoxification mechanism. It will enhance the mechanistic understanding on ROS and antioxidants system and will pave the path for agricultural scientists in developing tolerant crops to achieve sustainability under the changing environmental conditions. The increase in abiotic stress factors has become a major threat to sustainability of crop production. This situation has led to think ways which can help to come out with potential measures; for which it is necessary to understand the influence of abiotic stress factors on crops performance and the mechanisms by which these factors impact plants. It has now become evident that abiotic stress impacts negatively on plant growth and development at every stage of plant's life. Plants adapt to the changing environment with the adjustment at physiological, biochemical and molecular levels. The possible mechanisms involved in the negative effects of abiotic stress factors are excess production of reactive oxygen species (ROS). They alter physiological and molecular mechanisms leading to poor performance of plants. Plants however, are able to cope with these adverse effects by inducing antioxidant systems as the priority. Nevertheless, the dual role of ROS has now been ascertained which provides an evidence for regulation of plant metabolism positively on a concentration-dependent manner. Under conditions of high ROS production, the antioxidant system plays a major role in diminishing the effects of ROS. Thus, ROS production and antioxidant system are interwoven with abiotic stress conditions. The antioxidants have the capacity to hold the stability in metabolism in order to avoid disruption due to environmental disturbances.

Photosynthesis is a well-regulated process utilising solar energy for storage as chemical energy to meet the plant's metabolic needs. It is the key phenomenon that augments plant growth and development under all conditions and is considered as the ultimate source of life for all plant and human life. Although the basic processes of photosynthesis and their importance to the agricultural system for food security have been recognised about two centuries ago, there is an increasing need for intense research considering the population explosion. As the demand for food is expected to increase twofold by 2030, the efforts by plant scientists are necessary to improve the yield of food crops for sustainable development. The improvements in yield of crops can be attained by the protection of photosynthetic apparatus in the current changing environment, where degradation of soil, air and water quality has posed challenges to photosynthetic potential of plants. It has been estimated that the increasing salinization of land will result in the loss of 50% cultivated land by 2050. The situation will further aggravate with the contamination of soil and water by heavy metals. The concentration of CO2 is expected to rise to as much as 500-1000 ppm by 2100 which can lead to increases in global mean temperature by approximately 1 DegreesC to 3 DegreesC above the present value by 2025 and 2100, respectively. Photosynthesis is one the first processes inhibited under the changing environment leading to reduction of growth and productivity of plants.