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Wounding increased the extracellular Adenosine 5ʹ-triphosphate (eATP) level of kidney bean leaves. Treatment with wounding or exogenous ATP increased the hydrogen peroxide (H2O2) content, activities of catalase and polyphenol oxidase, and malondialdehyde content in both the treated and systemic leaves. Pre-treatment with ATP-degrading enzyme, apyrase, to the wounded leaves reduced the wound-induced local and systemic increases in H2O2 content, activities of catalase and polyphenol oxidase, and malondialdehyde content. Application of dimethylthiourea (DMTU) and diphenylene iodonium (DPI) to the wounded and ATP-treated leaves, respectively, reduced the wound- and ATP-induced local and systemic increases in H2O2 content, activities of catalase and polyphenol oxidase, and malondialdehyde content. Moreover, the wound- and ATP-induced systemic increases of these physiological parameters were suppressed when DMTU or DPI applied to leaf petiole of the wounded and ATP-treated leaves. These results suggest that eATP at wounded sites could mediate the wound-induced local and systemic responses by H2O2-dependent signal transduction. [ABSTRACT FROM AUTHOR]

Hypertonic salt stress with different concentrations of NaCl increased the levels of extracellular ATP of Arabidopsis leaves. And, hypertonic salt stress decreased the levels of Fv/Fm (the maximal efficiency of photosystem II), ΦPSII (the photosystem II operating efficiency), qP (photochemical quenching), and intracellular ATP (iATP) production. The treatment with β,γ-methyleneadenosine 5′-triphosphate (AMP-PCP), which can exclude extracellular ATP from its binding sites of extracellular ATP receptors, caused a further decrease in the levels of Fv/Fm, ΦPSII,qP, and iATP production of the salt-stressed Arabidopsis leaves, while the addition of exogenous ATP rescued the inhibitory effects of AMP-PCP on ΦPSII, qP, and iATP production under hypertonic salt stress. Under hypertonic salt stress, the values of Fv/Fm, ΦPSII, qP, and iATP production were lower in the dorn 1–3 mutant than in the wild-type plants. These results indicate that the responses of photosystem II and intracellular ATP production to salt stress could be affected by extracellular ATP. [ABSTRACT FROM AUTHOR]