The Effects And The Mechanism Of Auxins, CTKs On ABA-induced Stomatal Closure

The plant hormones auxins, cytokinins (CTKs) and abscisic acid (ABA) are important in the regulation of plant growth and development. Many researches showed that ABA induced stomatal closure by increasing the intracellular H₂O₂ (hydrogen peroxide) or NO (nitric oxide) in guard cells. Auxins and CTKs promoted stomatal opening by decreasing the intracellular H₂O₂ or NO in guard cells. Besides, it had been found that Auxins and CTKs could reverse ABA-induced stomatal closure. However, up to now, there was little information about the mechanism of the interaction of Auxins, CTKs and ABA in regulating stomatal movement. In order to integrate the intricate network of signaling pathway in guard cells and develop the mechanisms of stomatal movement, the effects and the mechanism of Auxins, CTKs on ABA-induced stomatal closure in Vacia faba were studied here by epidermal strip bioassay and laser-scanning confocal microscopy.The main results were followed:1. Auxins (IAA, NAA) and CTKs (6-BA, KT) reversed ABA-induced stomatal closure in a dose-dependent manner respectively.2. The effects of IAA, NAA, 6-BA and KT on reversing ABA-induced stomatal closure could be imitated by AsA (H₂O₂ scavenger), DPI (an inhibitor of superoxide generating NADPH oxidase), cPTIO (NO scavenger), and L-NAME (NO synthase inhibitor). It probably suggested that IAA, NAA, 6-BA and KT reversed ABA-induced stomatal closure by reducing the endogenous H₂O₂ or NO in guard cells.3. Utilizing the specific fluorescent indicator of H₂O₂ or NO and LSCM technique, it had been found that the increase of the endogenous H₂O₂ promoted by ABA could been prevented by IAA, NAA, 6-BA and KT, like AsA or DPI. And as cPTIO or L-NAME, IAA, NAA, 6-BA and KT could prevent the increase of the endogenous NO promoted by ABA .These results were in accordance with the epidermal strip bioassay. Thus, these results showed that the prohibitive effects of IAA, NAA, 6-BA and KT on ABA-induced stomatal closure were definitely related to the decreasing of the endogenous H₂O₂ or NO in guard cells;4. 6-BA and KT, like AsA or cPTIO, could promote the closed stoma induced by ABA to open. But, IAA and NAA, like DPI or L-NAME, could not promote the closed stoma induced by ABA to open. In other words, 6-BA and KT were similar to the...