| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 91 === The objectives of this study were to investigate the effects of pinching method on the morphogenesis of poinsettia ‘Peterstar’ and its evapotranspiration during growth and development, using coir dust and synthetic fiber to replace peatmoss for growing mix with slow released fertilizers under nutrient solution or watering only on growth, mineral composition of leave and medium leachate, photosynthesis and postproduction quality of poinsettia ‘Peterstar’.
The branch numbers of poinsettia decreased as pinching strength increased. Soft- and leaf removal-pinched plant which had 12.7 branch numbers and the hard-pinched plant had 8.0 branch numbers only. Besides no-pinched plant, the height to width ratio is non-significant in 0.59 to 0.63 among the other four pinching treatment. The bract area was 5082cm2 of soft-pinched plant which was largest among all treatment, and the bract area among the other four pinching treatment is non-significant in 3978 to 4401cm2. If want to use soft pinch to increase inflorescence number in the bract canopy, it must be removed immature leaves of the plant.
The maximum net photosynthesis rate(10.46-13.81CO2μmol.m-2s-1), saturated light intensity(429-822μmol.m-2s-1), and leaf chlorophyll a and b content of poinsettia were increased by the amount of fertilizer increased. The net photosynthesis and stomata conduction of the marketing stage were lower than the vegetative stage. With the poinsettia growth, the plant transpiration is increased when leaf number and leaf area increased, and reaching the maximum in bract show color stage and then decreased. In the regression analysis of 24 hours pot plant evapotranspiration during three growing stage in sunny or rainy day, the light intensity was the most important factor(r2 value is 0.8025) on evapotranspiration, among the effect of relative humidity is little, and temperature(16-24℃) is non-significant.
In four growing mixes, the air filled porosity are between 17 to 28%, the water holding capacity are between 62 to 72%, the EC value are between 0.6 to 1.2mS/cm, and the pH value all are about 6. Which are all in the range suitable for plant growth. The EC value of media leachate is increased with time of growth and the amount of fertilizer increased. The pH value of media leachate is decreased with time of growth. However, media leachate of Fafard growing Mix 1-P can maintain between 5 to 7. And using coir dust : synthetic fiber = 2 : 1 for growing mix, its pH value of media leachate is decreased below 4. The nitrogen, phosphate, and potassium content of media leachate reach the highest in 32 day after treatment, and then decreased.
Fafard Growing Mix 1-P for growing mix, the bract area of plant could reach 3791cm2 in watering and nutrient solution treatment. When using coir dust to replace 2/3 peatmoss, the highest bract area among treatment was 4013 cm2. But when using coir dust and synthetic fiber replace 3/4 peatmoss, the plant performance was not as well as Fafard Growing Mix 1-P. Postproduction quality could kept 3 month. The plant grown in coir dust : peat : synthetic fiber = 2:1:1 with ebb and flow culture had lowest growth confared with other two media(Fafard Growing Mix 1-P and coir dust : peat = 2 : 1). However, the quality of pot poinsettia still good enough.
In marketing stage, the leaf nitrogen content was between 4.35 to 6.15%, phosphate content was between 0.32 to 1.03%, and potassium content was between 0.93 to 3.43%. Leaf calcium content in all treatment was between 1.53 to 2.06%, and leaf magnesium content was between 0.65 to 0.91%. But the leaf calcium and magnesium content of using coir dust : synthetic fiber = 2 : 1 for growing mix is lower, especially the magnesium content is half of using Fafard Growing Mix 1-P for growing mix.
Calcium content in bract edge that using coir dust : synthetic fiber = 2 : 1 for growing mix is below 0.16%, and it showed calcium deficient symptom, caused decrease postproduction quality. So recommended that when using coir dust and synthetic fiber in growing mix, it should be mixed with dolomite and organic material which had high cation exchange capacity, for example peatmoss or composed bark.
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