Plant immune responses - from guard cells and local responses to systemic defense against bacterial pathogens.

When plants are infected by pathogens two distinct responses can occur, the early being a local response in the infected area, and later a systemic response in non-infected tissues. Closure of stomata has recently been found to be a local response to bacterial pathogens. Stomata closure is linked to both salicylic acid (SA), an essential hormone in local responses and systemic acquired resistance (SAR), and absisic acid (ABA) a key regulator of drought and other abiotic stresses. SAR reduces the effects of later infections. In this review we discuss recent research elucidating the role of guard cells in local and systemic immune responses, guard cell interactions with abiotic and hormone signals, as well as putative functions and interactions between long-distance SAR signals.