| Summary: | 碩士 === 國立臺灣大學 === 園藝暨景觀學系 === 105 === Cyclamen (Cyclamen persicum Mill.) is one of the most popular potted flowers worldwide, while slow and aberrant growth of plug seedlings and poor growth under high temperature condition are major production problems. It is important to produce high quality seedlings, reduce production period, and screen heat-tolerant cultivars. This study aimed to determine the effects of early feeding and optimum solution nitrogen (N), phosphorus (P), and potassium (K) concentration during plug stage on growth and subsequent flowering of Cyclamen ‘Laser Synchro Scarlet’. Effects of temperature on seed germination, plant growth, and flowering of eleven cyclamen cultivars were studied.
Days from sowing to the third leaf unfolding of Cyclamen ‘Laser Synchro Scarlet’ did not differ between seedlings applied weekly with 50% or 100% Johnson’s solution at root emergence and those applied with 100% Johnson’s solution when true leaves grew and developed. Seedlings with early feeding at root emergence had higher leaf area and dry weight, more flowers, and 2 weeks earlier to flowering than those applied when true leaves grew and developed.
Seedlings were applied with Johnson’s solution containing 0-28 mM N weekly from the first to the third leaf-stage. Results showed that N deficiency (0 mM) reduced whole plant net photosynthesis rate (Pn) and increased dark respiration rates, which resulted in poor growth, small and chlorotic leaves, low root activity and plant dry weight. Seedlings applied with 16-20 mM N had the highest Pn. Leaf area, SPAD-502 value, and plant dry weight increased with increasing N concentration from 0 to 20 mM, and did not increase significantly with increased N to 24-28 mM. Tissue carbon (C), N, P, and calcium (Ca) concentration increased with increasing solution N concentration. N-deficient seedlings had the lowest tissue magnesium (Mg) concentration, while solution N concentration did not affect tissue K concentration. After transplanting, seedlings applied with 24-28 mM N took the shortest time to flowering, and had the most flowers.
Seedlings were applied with Johnson’s solution containing 0-4 mM P weekly from the first to the third leaf-stage. Results showed that P-deficient seedlings had the lowest Pn, while there were no significant differences between P concentration treatments. P deficient seedlings were small, and had thicker and dark-green leaves. Leaf area and plant width increased with increasing P concentration from 0 to 1 mM, and did not differ between seedlings applied with 0.5-4 mM P. Plant and leaf dry weight did not differ between P concentration treatments. Increasing solution P concentration increased tissue P concentration, decreased tissue C concentration, but did not alter tissue N, K, Ca, and Mg concentrations. After transplanting, seedlings applied with 1 mM P took the shortest time to flowering and had the most flowers.
Seedlings were applied with Johnson’s solution containing 0-10 mM K weekly from the first to the third leaf-stage. Results showed that solution K concentration did not affect Pn and growth. Increasing solution K concentration from 0 to 10 mM increased tissue K concentration, decreased Ca and Mg concentration, but did not affect tissue C, N, and P concentrations. Days from transplanting to flowering were not affected by K concentration treatments. Seedlings applied with 6-10 mM K had the most flowers.
Eleven cyclamen cultivars, categorized in mini, midi, and maxi flower sizes, were sown at 5.2-30.1oC. Regardless of cultivar, the base and maxium temperatures for seed germination were similar as -0.6 and 35.6oC, respectively. The optimum temperature (To) for germination was 14.1-16.3oC, and the germination rate (the reciprocal of time to 50% seed to germinate) at To of mini cyclamen was faster than midi and maxi type. Eleven cyclamen cultivars were also cultivated in 9 cm pots, and grown at 20/15 and 30/25oC for seventy days. All cultivars at 30/25oC had bigger leaves, fewer flowers, and less compact than those at 20/15oC. Except that mini ‘Silverado Scarlet’ at 30/25oC had lower Pn than at 20/15oC. Pn of other cultivars did not differ between 30/25oC and 20/15oC treatments. As compared with midi and maxi type, mini cyclamen had higher stomatal conductance and transpiration rate (E), which resulted in lower leaf temperature at 30/25oC. Heat-tolerant mini ‘Smatiz Rose’, ‘Super Serie Vareno Dark Violet’, and ‘Metis Light Pink With Eye’ at 30/25oC maintained acceptable quality, with only slightly reduced flower and leaf numbers. Heat-sensitive mini ‘Silverado Scarlet’, maxi ‘Latina Success Deep Magenta’, ‘Halios HD Salmon’, ‘Sierra Synchro White’, and ‘Snowridge Maxi Purple’ at 30/25oC had poor quality and initiation ability of leaf and flower, more blasted flowers, and lower relative plant dry weight.
In conclusion, Cyclamen ‘Laser Synchro Scarlet’ applied weekly with 50% or 100% Johnson’s solution at root emergence or applied weekly with Johnson’s solution containing 24-28 mM N, 1mM P, and 6-10 mM K from the first to the third leaf-stage had good plug performances, more flowers, and took the shortest time to flowering. At 30/25oC, heat-tolerant mini ‘Smatiz Rose’, ‘Super Serie Vareno Dark Violet’, and ‘Metis Light Pink With Eye’ had higher E and lower leaf temperature, and maintained leaf and flower initiation, and quality.
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