A reduction in crop productivity in cultivable land and challenging environmental factors have directed advancement in indoor cultivation systems, such that the yield parameters are higher in outdoor cultivation systems. In wake of this situation, light emitting diode (LED) lighting has proved to be promising in the field of agricultural lighting. Properties such as energy efficiency, long lifetime, photon flux efficacy and flexibility in application make LEDs better suited for future agricultural lighting systems over traditional lighting systems. Different LED spectrums have varied effects on the morphogenesis and photosynthetic responses in plants. LEDs have a profound effect on plant growth and development and also control key physiological processes such as phototropism, the immigration of chloroplasts, day/night period control and the opening/closing of stomata. Moreover, the synthesis of bioactive compounds and antioxidants on exposure to LED spectrum also provides information on the possible regulation of antioxidative defense genes to protect the cells from oxidative damage. Similarly, LEDs are also seen to escalate the nutrient metabolism in plants and flower initiation, thus improving the quality of the crops as well. However, the complete management of the irradiance and wavelength is the key to maximize the economic efficacy of crop production, quality, and the nutrition potential of plants grown in controlled environments. This review aims to summarize the various advancements made in the area of LED technology in agriculture, focusing on key processes such as morphological changes, photosynthetic activity, nutrient metabolism, antioxidant capacity and flowering in plants. Emphasis is also made on the variation in activities of different LED spectra between different plant species. In addition, research gaps and future perspectives are also discussed of this emerging multidisciplinary field of research and its development.

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Highlights Rice is a staple food for more than three billion people, and rice cultivars have evolved over thousands of years of adaptation to different environmental stresses in different regions. Domestication of rice cultivation led to the diversity of cultivars though phenotypic selection for desirable characters. India is blessed with great diversity of rice germplasm, and these are still conserved for many reasons. The aim of the study was to show the seedling-stage salt tolerance of a total of 50 indigenous rice genotypes from coastal Tamil Nadu, India. Using a hydroponic system, we studied the different agronomic characters from seedling to plant growth hight 14 days after exposure to six different concentrations of saline solution. Rice genotypes showed significant interaction and differential response towards salinity were assessed at the molecular level using simple sequence repeat (SSR) markers linked with salt-tolerance QTL. We found wide genetic distance among the genotypes studied. The combination of morphological findings and molecular assessment revealed better salt-tolerance in a few genotypes. This is, to the best of our knowledge, the first study on the indigenous rice landraces of coastal Tamil Nadu, India.

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