Breakthroughs spotlighting roles for extracellular nucleotides and apyrases in stress responses and growth and development

•The importance of receptor discovery for extracellular nucleotide signaling is critiqued.•How downstream signaling changes leading from receptor activation to growth changes is discussed.•The potential functions of apyrase enzymes in turning off the eATP signal and in regulating growth are evaluated.•The new phylogenetic and structural analyses of plant apyrases are provided.•The relationship of apyrases and eATP signaling to biotic and abiotic stress responses is documented and discussed.