Human beings and plants experience a variety of stress conditions and adapt themselves through novel molecular crosstalk in their cellular constituents. Nitric oxide (NO), haemoglobin and melatonin interact with each other not only in blood stream of human beings, but also in the cells and metabolically active conducting strands of plants. Specialised sites of biosynthesis and differential intracellular spatial distribution of these molecules have been clearly demonstrated by the authors in plant systems. This has led to an understanding of the role of these molecules under salt stress conditions experienced by plants: NO is a modulator of enzyme activity through S-nitrosylation and tyrosine nitration, haemoglobin (phytoglobin) is an NO scavenger, and melatonin is a reactive oxygen species (ROS) scavenger involved in key crosstalk in both plants and humans facing stress. Our recent work on heme oxygenase (HO) activity modulation by stress in plants, and its interaction with NO, further demonstrates common features of molecular crosstalk in protecting plants and human beings from stress.