The role of boron in biological systems with focus on legumes in crop production - A review

Boron (B) has during the last century been considered as an essential micronutrient for higher plants. An increasing amount of data also support the view that B has a function in important life processes in animals and humans, and that low concentrations in food and feed can result in deficiencies that contribute to severe diseases. The primary function of B in biological systems is still not clear. The overall aim of this review is to give a broad perspective of the role of B in soil/plant interactions. Boron sources in nature, B biochemistry, and the physiological action of B in plants are described. Also presented are the consequences of B deficiency for plant growth, symbiotic associations, susceptibility to plant diseases and sensitivity to environmental stressors. Short notes about the role of B in animals and humans intend to underline that B in animal/human diets needs more attention. The particular focus of this chapter is on the role of B in the use of legumes in crop production, and an application of the described facts on legume crops is presented. Besides using legumes for feed and food production, legumes are practically necessary in crop rotations in organic production and in other cropping systems relying on biological processes, e.g. symbiosis (N₂ - fixing bacteria e.g. Rhizobia ssp and mycorrhizal fungi). A ley crop, established from a mixture of legumes, grasses and sometimes herbs, contribute to the development of the whole system including soil structure, nutrient balance, and pest and weed control. The importance of legumes in crop production in a local and a global perspective is stressed. In this chapter, recent literature on the role of B in biological systems with a focus on legumes in crop production systems has been reviewed. Knowledge gaps and future research areas are suggested.