藍莓頂梢開花形態形成與物候研究

Abstract

藍莓(Vaccinium spp.)為原生於北美洲的落葉或常綠性灌木植物。在溫帶地區，藍莓花芽於秋季形成於葉腋後，進入休眠並於翌年春季開花。然而栽培於臺灣平地的藍莓，於秋季仍持續生長的枝梢頂端，常發生直接開花結果的現象，此不時花具一年二收或產期調節之潛力。本論文透過調查田間栽培之藍莓植株、與觀察各品種頂梢於秋季芽體分化之顯微結構，期望找出較易發生頂梢開花現象之品種，並探討頂梢開花可能的產生機制。試驗假說為臺灣平地秋季氣溫有利於藍莓營養生長，同時期之光週期則有助於花芽分化。兩年度的田間調查結果顯示，兔眼藍莓(V. virgatum Aiton)秋梢停止生長時間點較南高叢(V. hybrid)及北高叢藍莓(V. corymbosum L.)晚，在9月底至10月底之間，尚有高比例的秋梢尚未停梢，而多數易頂梢開花之品種亦屬於兔眼藍莓。2019年9月22日至10月22日間之氣溫較2018年同時期高，頂梢花芽分化之數量則較少。芽體觀察試驗結果顯示，若枝梢於適合花芽創始之環境條件下仍持續發育，即產生頂梢開花。比較兩試驗年度秋季之氣溫差異，日均溫介於20與25℃間似可促進頂梢花芽分化，超過27℃或低於20℃則有抑制作用。

Blueberries (Vaccinium spp.) are deciduous or evergreen bushes native to North America. In temperate regions, flower buds of blueberries differentiate in leaf axil before winter dormancy and bloom in the next spring. However, in lowland Taiwan, blueberries often produce flowers and bloom directly on growing shoot apices in autumn, such off-season blooming offers potentials for forcing culture. This thesis investigated field grown blueberry plants and observed bud microstructures of apical and axillary buds sampled from various blueberry cultivars to evaluate the tendency and the possible mechanism of apical flowering. The hypothesis was that in lowland Taiwan, mild autumn temperature favors vegetative growth, and the shortening photoperiod favors reproductive growth of blueberries, consequently inducing apical flowering. The result of two-year observations showed that during late September to late October, a high percentage of growing shoot tips was observed in rabbiteye blueberries (V. virgatum Aiton) than in southern (V. hybrid) or northern highbush blueberries (V. corymbosum L.). Cultivars that produced more apical flowering shoots belonged to rabbiteye blueberries. Between late September and late October, less apical flowering shoots were observed in 2019 than in 2018 during the same period. Weather data indicated that during this period, mean temperature was higher in 2019, which might have reduced of the tendency of apical flower differentiation. Microstructure of apical bud showed that in conditions favored flower differentiation, shoots that were still actively growing tend to develop flowers directly in the shoot tips. Daily mean temperature around 20℃-25℃ seemed to promote apical flower bud differentiation, while temperatures above 27℃ or below 20℃ posed negative effects.