溫度對小蒼蘭生育與花期調節之影響

Abstract

本論文研究溫度對小蒼蘭生長與開花之影響、探討種植前球莖涼溫乾貯對日後生育與開花之影響、並進行品種之生長與開花特性調查，以建立小蒼蘭在台灣本土之花期調節資料。 將已經打破休眠的‘Elysee’與‘Senator’兩個品種球莖種植於人工氣候室15/13℃、20/15℃、25/20℃、30/25℃與35/30℃五種溫度下，生長在25/20℃下植株有較多的葉片數、葉面積及葉乾重，顯示25/20℃適合兩個品種營養生長，而13-20℃較適合小蒼蘭開花，從定植到開花約在115 - 120天左右，兩個品種花梗長度都以20/15℃處理者較長。兩個品種新球乾重與牽引根乾重都以20/15℃與15/13℃處理組最重，且有隨著處理溫度升高而降低的趨勢。葉綠素含量隨著處理溫度降低而升高，以15/13℃最多，而30/25℃最少。 在花芽分化前小蒼蘭植株先以25/20℃處理5-7週，可增加葉片數而提高花梗長度與側花梗數。在15/13℃與20/15℃或十一月在梅峰種植6週後，小蒼蘭植株皆已進入生殖生長，花芽分化後的植株如維持在9℃的低溫下會造成開花延遲，以維持在13-20℃較佳。當花梗長度生長至2-10 cm時，將溫度調整至20/15℃可增加花梗長度或縮短到花日數。 小蒼蘭球莖先以10℃乾貯5-9週後，再種植於13-20℃溫度下可以提早花期，但葉片數、花梗長度、花朵大小、花朵數及側花梗數等都隨10℃乾貯時間增加而減少。球莖10℃乾貯週數如超過7週，種植後蛹化球的比率急速增加而導致萌芽率急速減少，故10℃乾貯週數不宜超過7週。 小蒼蘭球莖10℃乾貯後再移到 25/20℃栽培者，開花率低且畸形花情形嚴重，以移到13-20℃較佳。小蒼蘭球莖先以10℃乾貯3週或以20℃乾貯3週後再移至10℃乾貯3週者，如種植於20℃以下的設施內，到花日數可提早36-40天，兼具了提早花期並有較佳的花梗長度與側花梗數的優點，可解決因高溫造成的花芽分化延遲問題。相較於球莖濕貯，球莖乾貯處理具有節省冷藏空間與種植人工的優點。 參試的19個品種生長與開花特性調查結果顯示，早生品種較早停止葉片分化且較早轉變為生殖生長而提早開花，而晚生品種則分化了較多的葉片數而延遲開花，將各品種之到花日數與其花下葉片數進行廻歸分析，結果兩者呈直線正相關。‘Rapid Yellow’、 ‘Rapid Pink’、 ‘Focus’等早生品種，種植後到花日數少於100天，雖然側花梗數較少，花梗長度較短且花朵較小，但開花較不受高溫的影響而延遲，故在溫度較高的地區或季節可以栽培早生品種以調節花期。

In order to establish the information on regulation of flowering in freesias (Freesia ×hybrida) in Taiwan, effects of temperature on growth and flowering, temperature and duration during preplant corm dry storage on subsequent flowering were studied in freesias, and growth and flowering characteristics for 19 cultivars was also determined. Corms of ‘Elysee’ and ‘Senator’ released from dormancy were planted at day/night temperatures of 15/13℃, 20/15℃, 25/20℃, 30/25℃ and 35/30℃in phytotron conditions. Maximum leaf number, leaf area and leaf dry weight were measured in plants at 25/20℃. After planting for 115 to 120 days, plants at 13-20℃ flowered while plants at higher temperatures did not. Plants at 20/15℃ produced longest flower stalk. Contractile root, new corm dry weight and SPAD value decreased with increasing temperature. Leaf number before flower initiation was increased with the 25/20℃ treatment for 5-7 weeks, and therefore plants had longer flower stalk and more lateral flowering shoots. Freesias had flowers initiated after the 15/13℃ and 20/15℃ treatments, or planting at Mei-Feng in November for 6 weeks. Flower stalk length was increased or flowering time was shorten, when applying 20/15℃ to plants with flower stalk length about 2 to 10 cm. Flower development after initiation was delayed under winter to early spring conditions (mean 9℃) in Mei-Feng, but was promoted with 13 to 20℃ in Puli conditions. Preplant corm dry storage at 10℃ for 5 to 9 weeks accelerated flowering of freesias grown in 13-20℃ conditions. Leaf number, flower stalk length, flower size, flower number and lateral stem decreased with increasing dry 10℃ storage duration. Pupation percentage increased and sprouting percentage decreased sharply when dry storage duration at 10℃ for 7 weeks or longer. In contrast, preplanting corm dry storage at 10℃ reduced percentage of flowering and caused malformed inflorescences in freesias grown in 25/20℃. Flowering time was shorten by 36 to 40 days, provided that the plants were grown at 20℃ following preplanting storage at 10℃ for 3 weeks or at 20℃ for 3 weeks and then transferred to 10℃ for 3 weeks. Preplanting dry storage could reduce requirement for cooling system space and time for planting, as compared with wet storage. Growth and flowering characteristics for 19 cultivars were investigated under Mei-Feng conditions. The early flowering cultivars had fewer leaves before flowering, suggesting that early flowering was largely due to flower initiation. A linear relationship existed between days to flowering and leaf number below inflorescence for the cultivars. Although the early-flowering (< 100 days) cultivars Rapid Yellow, Rapid Pink and Focus had shorter flower stalk length, fewer lateral flowering shoots, and smaller flowers, these cultivars were more heat-tolerant and could be grown in warmer conditions.