Fig. 2: Identification of signals that can be direct generic or specific abiotic signals or indirect signals via biotic interactions.

Direct generic signals are related to abiotic factors such as chemical compounds like exudates and volatiles and light quality such as the red to far-red ratio (R:FR), resources such as nutrients and mechanical stimuli. Direct specific signals are chemical compounds in exudates or as volatiles that have a specific composition that can signal a specific crop species. Indirect biotic signals are signals from a crop species that are mediated by microbes, invertebrates and arable flora within the system.