Application of abscisic acid

Several papers have reported that, during germination, new LOXs are synthesized in the seedling and the cotyledons the LOX mRNAs synthesized during germination can also be found in the mature plant. Their levels were increased by the application of abscisic acid and jasmonic acid, or by stress such as wounding, pathogen infection, or water deficit (Porta and Rocha-Sosa 2002). 

The stimulation of the closure of abaxial stomata after the application of abscisic acid of Commelina communis was inhibited by La (De Silva et al. 1985). The action of cytokinin in stimulating the adventitious bud initiation in Torenia step segments was inhibited by 0.3 mM LaClj (Tanimoto and Harada 1986). The consequences of this effect on crop yield is theoretically quite severe. 

Cytokinins have also been reported to increase PA biosynthesis in some plant systems, while application of abscisic acid (ABA) leads to the contrary situation (see review in Smith, 1985a). For instance, benzyladenine increased putrescine and ADC activity in cucumber cotyledons. By contrast, ABA decreased putrescine and ADC activity (Suresh et ai, 1978 In rice seedlings, total PAs increased threefold after treatment with kinetin, but declined with ABA (Mukho-padhyay et ai, 1983). It has been proposed that the regulation of PA biosynthesis by ABA in the aleurone layers of barley seeds is exerted through inhibition of the conversion of putrescine to spermidine (Lin, 1985). 

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