影響榴槤（Durio zibethinus Murr.）結實之因子Ⅰ、開花與授粉

Factors Affecting Fruitfulness in Durian (Durio zibethinus Murr.). Ⅰ. Flowering and Pollination

榴槤屬（Durio）共有七個可食用種，即D. zibethinus Murr.、D. kutejensis（Hass.）Becc.、D. oxleyanus Grif.、D. graveolens Becc.、D. testudinarium Becc.、D. dulcis Becc.及D. grandiflous（Mast.）Kost. & Soeg.，其中D. zibethinus Murr.是一般主要栽培種（俗稱durian）。榴槤原產東南亞，婆羅洲及蘇門答臘為其變異中心，目前主要生產於泰國、印尼及馬來西亞等國家。在泰國的自然氣候條件下，15～20天的連續乾旱即可滿足榴槤的花芽分化。榴槤的花芽發育約需60天左右，可以依形態細分成七個階段。一般花朵是在下午四點綻放，花藥在晚上七點開始開裂。雄蕊、花瓣、萼片等自晚上十一點即開始掉落，至隔天早上十點多數小花即脫落到僅剩下雌蕊。柱頭在開花前後24小時內均有受粉的能力，但以開花後12小時內最高。花粉自花藥開裂後，在室溫下儲放24小時仍有七成以上之萌發率。榴槤之結實率因品系而異，有些品種自交結實率甚低（<10%），通常異交可提高著果率達到49%。已鑑定之自交結率低的品系有：‘D99’、‘D24’、‘Gumpun’及‘Luang’等`，此外‘Monthong’及‘Chanee’兩品種也有自交下結實率偏低之現象。榴槤花粉對果實之發育有果實直感效應（metaxenia effect），可以影響果實之熟期，結實率與果實品質，所以建園要有適當授粉樹之配置，並慎選授粉樹品種。其他改善榴槤結實率之方法尚有實施人工授粉、蝙蝠保育等工作。

There are seven species that yield edible fruit in genus Durio: D. zibethinus Murr., D. kutejensis (Hass.) Becc., D. oxleyanus Grif., D. graveolens Becc., D. testudinarium Becc., D. dulcis Becc. and D. grandiflous (Mast.) Kost. & Soeg., with D. zibethinus as the major cultivar(local name is durian). Durians are native of South-East Asia with Borneo and Sumatra as the centers of diversity. Thailand, Indonesia and Malaysia are the major production country. The main production season, starting from March till December, is believed to be affected by the dry-wet season in production areas. In general, the floral initiation is achieved when the draught stress lasted for 15-20 days. A whole floral development needs about 60 days that can be divided in to seven stages. Flowering habits are different among individual species. Generally, Durian flower starts to bloom at 16:00, pollen sheds from 19:00, and floral parts begin to abscise around 23:00. All of the floral parts except the gynoecium will have abscised by 10:00 on the following day. Stigma is receptive within 24 hrs before and after full bloom, but receptivity achieves the maximum within 12 hrs after full bloom. The viability of pollen after shedding can maintain high viability (＞70%) of germination when stored in room temperature within 24 hrs. The main pollinator of Durian appears to be bats. Fruit set rate is different among cultivars, however, the fruit set of selfing is poor (＜10%) for some cultivars, and improves greatly with cross-pollination. Some cultivars, for example, 'D99', 'D24', 'Gumpun' and 'Luang' have been shown to be of low productivity. Beside this, 'Monthong' and 'Chanee' also exhibit low productivity when selfing. The metaxenia effects of Durian pollen influenced the harvest time of fruit, fruit set and fruit quality. So the pollination tree should be arranged in the orchard with a careful selection of pollination tree cultivar. Alternatively, hand pollination and bats conservation can improve fruit set.