‘Merton Thornless’黑莓於臺北地區花芽創始及發育之研究

Abstract

黑莓(Rubus subgenus Rubus Watson)為薔薇科懸鉤子屬，枝條二年生之宿根性小果類作物。短日及涼溫誘導大部份懸鉤子屬植物行花芽創始，但各地區之花芽創始時間則因品種及當地氣候而異。黑莓在臺北地區花芽創始之時間及冬季花芽分化情形尚未有人研究。許多黑莓在溫帶地區秋季時經環境誘導行花芽創始，而臺北地區冬季氣溫條件及日長與溫帶地區的秋季類似，應可誘導黑莓行花芽創始。本試驗分為兩部分：第一部分從2013年9月開始，每月切取盆植之四年生‘Merton Thornless’黑莓的當年生營養枝上不同區段之腋芽，以觀察其花芽創始之時間及冬季花芽分化情形，同時調查物候。第二部分在2015年的1月及2月催芽，觀察催芽對花序形成及植株物候之影響。 2013年試驗結果，植株腋芽之莖頂面積從2013年12月開始逐漸增大，顯示臺北地區冬季可誘導腋芽從營養態轉變為生殖態，但截至2014年5月份之結果，僅有一腋芽分化至具萼片原基，大部份的腋芽皆未行花芽創始。這種花芽形成的模式可能跟‘Hull Thornless’黑莓在西維吉尼亞州的表現類似，腋芽先經環境誘導轉變為生殖態，隔年春季萌芽後行花芽創始，接著發育花序。再者，由於涼溫下(15到24°C)適合黑莓生殖生長，因此在2015年1月及2月以二氯乙醇溶液催芽後，2月及3月萌發且形成側枝的腋芽皆有發育出花序，但4月後始萌發之腋芽則只形成側枝而未發育出花序。 ‘Merton Thornless’黑莓在臺北自然條件中物候期如下：3至4月時當年生枝條從前一年枝條基部的冠芽長出，接著可持續生長至12月，12月至1月間，腋芽經環境誘導轉變為生殖態，同時逐漸進入內生休眠，隔年4月時萌芽，接著花芽分化及花序發育，5月時開花，7月時結果。若在1、2月時催芽，可使植株開花提前至4月，結果提前至6月。

Blackberry (Rubus subgenus Rubus Watson) is a perennial small fruit crop with biennial canes. In general, flower initiation of most brambles is induced by short day and cool temperature, but the timing varies among cultivars and local climates. There is no report on the flowering phenology of blackberries in Taipei. Many blackberries commence flower initiation in the autumn of temperate zone. Because the temperature and day length of winter in Taipei are similar to autumn in temperate zone, flower initiation of blackberries may be induced by the short day and cool temperature in the winter of Taipei. In the first part of this thesis, axillary buds of potted ‘Merton Thornless’ blackberries were sampled monthly from different sections of primocanes, and the timing of flower initiation and flower differentiation were determined. The natural phenology was recorded. In the second part of this thesis, dormant buds were forced in January and February 2015. The effects of bud forcing on the formation of inflorescence and phenology were investigated. The shoot apex surface area of axillary buds gradually increased in December 2013, indicating that axillary buds had been induced from vegetative state to reproductive state. However, by May 2014, most axillary buds had yet commenced flower initiation. The mode of flower bud formation is similar to the ‘Hull Thornless’ blackberry in West Virginia in which the axillary buds were induced to transform to reproductive state before winter, but flower initiation had not commenced until budbreak in the next spring. Cool temperature (15-24°C) is required for reproductive growth of blackberries. Therefore, after bud forcing in January and February 2015, the axillary buds that broke dormancy in February and March generated laterals and formed inflorescences. On the other hand, those broke dormancy after April developed into laterals but failed to form inflorescences. The phenology of ‘Merton Thornless’ blackberries under natural condition of Taipei was described. Primocanes grow from the crown buds and continue growing until December. Axillary buds are induced by short day and cool temperature to reproductive state between December and January. Axillary buds resume growth in the following April and then commence flower differentiation and inflorescence development. Flowering and fruiting take place in May and July, respectively. After bud forcing in January or February, flowering and fruiting were advanced to April and June, respectively.