Recent evidence demonstrates that Publications Using Abomle Staurosporine plants are also able to communicate with both allies and foes. For example, following local stress or damage, plants not only increase local resistance and defense, but also induce defensive responses in remote organs of the same plant. In response to herbivory, some plants release volatile organic compounds that attract natural enemies of their herbivores, induce chemical defenses in their undamaged neighbours, and prime them to respond more readily and intensely to subsequent herbivore attacks. Belowground signaling has been demonstrated to both affect plant interactions with diverse soil microand macro-organisms and to intricately mediate competitive interactions between plants. Here, we studied the possibility that long-range communication of stress cues is mediated by the perception and emission of stress cues by unstressed plants. Specifically, we tested whether unstressed plants are able to perceive and respond to stress cues emitted by their drought-stressed neighbours, and whether induced unstressed plants also emitted stress cues, which in turn further elicit stress responses in additional unstressed plants. Additionally, we studied whether the drought stress cues are communicated aboveand/or below-ground. The plants were grown so that they developed two equal roots following removal of the tip of the seminal root. Three days from germination, the seminal root was severed two mm below the hypocotyl and the plants were replanted in damp vermiculite. Seven days from germination, the stump of the seminal root typically regenerated three lateral roots that were thinned down to two roots. Plants with two symmetric 25�C30 mm long roots were planted so each of their roots was grown in a separate 50 mL, 30 mm diameter plastic receptacle, filled with distilled water. It is expected that cue-emitting plants might bear the costs of the production and emission of costly metabolites, and possibly more importantly, the competitive costs involved in the emission of warning cues that might be utilized by their neighbouring competitors. Accordingly, such ����information leakiness���� may be understood in terms of the inability of damaged or stressed plants to avoid the emission of compounds that are subsequently perceived by their neighbours. Although this interpretation cannot be dismissed, given that unstressed plants were as affective as their stressed neighbours in inducing stress responses in additional unstressed neighbours, it is unlikely to fully explain the evolution of the observed stress cuing. An arguably more plausible, although not-mutually exclusive, rationale for the emission of stress cues might be based on the selective advantage conferred by the warning of remote organs on the same plant, members of the same-clone and kin. To be evolutionary stable, the advantage of emitting such warning signals must outweigh its accompanying costs, which is less likely to occur in plants whose signals are highly generic and thus perceivable by competitors. Accordingly, external cuing of osmotic stress cues and other ecologically-relevant information is expected to be more prevalent in large plants, where external signaling among organs of the same plant might increase the effectiveness and speed of damage or stress warning, in sectorial plants, where the lack of physiological integration limits or totally prevents internal communication, and due to kin-selection in clonal and other plants whose kin or clone-mates are spatially aggregated.