Root growth profiles of Aveneae and Poeae plants in optically active α-methylbenzyl-3-p-tolylurea media

Using a root growth inhibition assay, we studied the diverse chiral responses of plants in the tribes, Aveneae and Poeae, to the optically active compounds, R- and S- 1-α-methylbenzyl-3- p -tolylurea (MBTU). We specifically examined the responses of grasses belonging to the Poeae tribe ( Lolium , Briza , Poa , Dactylis , and Festuca ) and the Aveneae tribe ( Avena , Holcus , Agrostis , Alopecurus , Beckmannia , and Phleum ). These plants include companion weeds of wheat and barley, and turf grass. The companion weeds of cereal crops, such as Poa annua , Poa pratensis , Dactylis glomerata , Avena fatua , Avena sativa , Holcus lanatus , Agrostis stolonifera , Alopecurus myosuroides , Al. aequalis , and Beckmannia syzigachne , showed significantly inhibited root growth in response to 20 µmol L⁻¹ R- MBTU, whereas the root growth of Triticum aestivum was not inhibited at this concentration. Like Oryza sativa , almost all the Poeae and Aveneae plants tested here preferentially responded to R -MBTU, but the four grasses, Lolium multiflorum , D. glomerata , Alopecurus species, and Phleum pratense , preferentially responded to S -MBTU. Among them, the Agrostis species were highly sensitive to R -MBTU and the Alopecurus species were highly sensitive to S -MBTU. All the plants among the genera, Poa , Avena , and Alopecurus , showed a homogeneous chiral preference.     

Triticeae plants preferentially responded to S-1-α-methylbenzyl-3-p-tolylurea in root growth and tetrazolium reduction assays

Optically active 1-α-methylbenzyl-3- p -tolylurea (MBTU) shows diverse plant physiological properties. Gramineae plants exhibit enantioselective root growth inhibition by R / S -MBTU. In the present paper, the dose–growth response (DGR) towards the optically active MBTUs was examined in the tribe Triticeae plants, including Hordeum vulgare L., Secale cereale L., Triticum aestivum L. and Aegilops cylindrica Host., and compared with those of the genus Bromus ( B. inermis Leyss), which is classified into the tribe Bromeae, and the genus Oryza . In spite of their phylogenetic difference, the Triticeae plants responded homogeneously in their chiral recognition. Of particular interest, is the result of the dichotomic enantioselective response of tested Gramineae plants. Only the genus Oryza responds to R -MBTU, and the tribes Triticeae ( Triticum , Aegilops , Secale and Hordeum ) and Bromeae ( Bromus ) preferentially respond to the S -enantiomer. The tetrazolium–phenazine methosulfate–formazan (TPF) assay was demonstrated to measure redox activity of root tips of the MBTU-treated Oryza sativa and T. aestivum , which are the typical dichotomic, enantioselective-responsive plants. In Oryza and Triticum root tips, enantioselective responses of reduction activity in TPF assays were strongly related to those of root growth inhibition in DGR assays, suggesting aggressive participation of the MBTU in the generation of the reducing mechanism in mitochondria.