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Experimental Design

Planting material 
Two cultivars of myoga, one high yielding and the other low yielding under Tasmanian conditions (referred to as Superior (S) and Inferior (I) respectively) were used in this study. Plant material was propagated vegetatively from myoga plants grown in two different locations. Cultivar S rhizomes were collected in winter from dormant field grown myoga plants at New Norfolk, Tasmania while cultivar I rhizomes were taken from plants grown in a shadehouse at the University of Tasmania. The rhizome material was soaked in a fungicide treatment consisting of 100ml of Previcurâ, 200ml of Bainstonâ, 100ml of Sumisclexâ and 200g of Koadeâ per 100 l of water. It was then packed into seed trays filled with a moistened mix of 50% perlite, 25% coarse sand and 25% peat and given a standard chilling treatment of three weeks at 40C (Gracie et al, 2000). Approximately 50g rhizome pieces were then planted into separate 20 l pots. The potting soil consisted of peat, sand and pine bark (1:2:7) which was supplemented with slow release fertiliser (nine month Osmocoteâ 330g/50 l), dolomite lime (330g/50 l), iron sulphate (25g/50 l) and trace elements (Micromaxâ 20g/50 l). The pots were watered daily. Irrigation and fertiliser programmes were identical for each of the treatments.

Photoperiod treatments
Three photoperiod treatments were imposed. All plants received 8 hours natural daylight in the glasshouse, this was followed by either 16 hours of darkness (SD treatment), 16 hours darkness with 60 minutes night break lighting in the middle of the dark period (SD + night break lighting treatment) or 8 hours supplemental lighting followed by 8 hours darkness. A motorised trolley system was used to transfer plants from a common glasshouse space to individual controlled environment cabinets. Supplemental and night break lighting was provided by combined mercury vapour and fluorescent lights with a photosynthetic photon flux density of 30.2 mmol.m-2.s-1. Glasshouse light levels ranged from 600 to 1200 mmol.m-2.s-1. Average temperature in the glasshouse was 250C, and all three environment cabinets were maintained at an average temperature of 170C. Due to space constraints true replication was not achievable in the experimental design, however continuous monitoring of the cabinets ensured that the temperature and photoperiod regimes remained constant. Ten cultivar S plants and ten cultivar I plants were placed into each treatment. There were two harvests, the first at 104 days after planting (DAP) and at 201 DAP. At each harvest five cultivar I plants and five cultivar S plants were destructively sampled from each photoperiod treatment. Means and standard errors for the mean for each sample, (n = 5) were calculated.

At each harvest, plants were removed from their pots, potting mix washed off and the above and below ground parts of the plant separated. The above ground material (pseudostems) was weighed and then dried to obtain wet and dry weights. The rhizomes and roots were stored at 20C. Rhizomes were later dissected and apical meristems examined to determine if flower bud initiation had occurred and whether initiated flower buds had aborted leaving a senescent primordium. In the second harvest, mature and developing flower buds were removed from the plant and individually weighed and counted.

Click to animation - Myoga photoperiod simulation

Click to worksheet - Analysis of Experimental Design

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