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  • Author or Editor: Annette Chandler x
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Common liverwort (Marchantia polymorpha L.) is an increasingly troublesome weed in containerized plant production. Postemergence applications were made to try to eradicate established stands of liverwort. Treatments consisted of sprays of quinoclamine at 1× and 2× rates and oxadiazon at the highest label rate, broadcast applications of sodium carbonate peroxyhydrate at 1x and 3x rates and four granular herbicides (flumioxazin, oxadiazon, oxyfluorfen + pendimethalin, and prodiamine) applied at label rates. The granular herbicides were applied both alone and with the sodium carbonate peroxyhydrate treatments. Herbicides were applied to common liverwort growing on an 80% aged pine bark: 20% Sphagnum peat-based soilless growing medium contained in 10-cm diameter plastic pots located in a double-poly covered greenhouse. At 2 weeks after treatment (WAT), control was best (93% to 100%) for both quinoclamine and the 3× peroxyhydrate treatments, intermediate (68% to 83%) for the 1× peroxyhydrate treatments, and not significant for any of the preemergence herbicides used alone. At 4 WAT, slight regrowth was evident in plots in which the treatments had an initial effect and the 1x peroxyhydrate + flumioxazin was as effective as the 3× peroxyhydrate and the 2× quinoclamine treatments. At 6 WAT, control was excellent in the 3× peroxyhydrate and 1× peroxyhydrate + flumioxazin treatments. Control was less, but still evident, in the quinoclamine and other 1× peroxyhydrate treated plots. While none of the treatments had completely eradicated common liverwort in all replications at 10 WAT, control was still excellent to good in many of the peroxyhydrate + preemergence herbicide-treated plots.

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Desiccation of containerized plants at retail outlets due to inadequate watering is a recurring problem. Water stress can decrease plant quality and survivability. Treatments that could reduce plant transpiration without lowering plant quality could be beneficial in maximizing the likelihood that plants would not become water stressed between waterings at retail outlets. Abscisic acid (ABA) is known to be involved in the regulation of stomatal aperatures, the major control mechanism for transpirational water loss. Containerized plants of four cultivars of hibiscus were thoroughly sprayed with S-ABA at concentrations of 0, 125, 250 or 500 mg·L–1. Plants were held under simulated retail conditions and were not watered until visible wilting occurred. Transpiration and pot weights were monitored over time. Transpiration rates and weight loss percentages were negatively correlated with S-ABA concentrations. Effects on transpiration rates lasted for at least 30 hours after treatment. For mean hours to wilt, there was interaction between S-ABA treatments and cultivars. For the most sensitive cultivar (`Double Apricot'), treatment with S-ABA at 500 mg·L–1 almost doubled the time to plant wilt (130 h) compared to the control treatment (72 hours). Hours to wilt was increased 24% for `Double Pink' treated at the highest rate. For `Double Red' and `Single Pink', hours to wilt was not affected by treatments. For some hibiscus, S-ABA treatments prior to placement of plants at retail outlets might decrease the chances that the plants would become severely water stressed.

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