Hee Kim Hor, Loh Chiang Shiong, Yeoh Hock Hin
Department of Biological Sciences, National University of Singapore, Singapore.
Plant Cell Rep. 2007 Dec;26(12):2055-62. doi: 10.1007/s00299-007-0421-9. Epub 2007 Aug 7.
Plantlets of Dendrobium Chao Praya Smile maintained in vitro were induced to flower, which produced viable seeds within about 11 months. A two-layer (Gelrite-solidified layer topped with a layer of liquid medium of the same volume and composition) culture system containing benzyladenine (BA) at 11.1 muM induced the highest percent of flowering (45%) in plantlets within 6 months from germination. The percentage of inflorescence induction was increased to 72% by pre-selecting morphologically normal seedlings prior to two-layer culture. Plantlets in culture produced both complete (developmentally normal but smaller than flowers of field grown plants) and incomplete flowers. Pollen and female reproductive organs of in vitro-developed complete flowers were morphologically and anatomically similar to flowers of field grown plants. In addition, 65% of the pollen grains derived from in vitro-developed flower were tetrad suggesting that regular meiosis occurred during microsporogenesis. The percentage of germination of pollen grains derived from in vitro-developed flowers and flowers of field grown plants, incubated on modified Knops' medium for 8 days, were 18.2 and 52.8%, respectively. Despite a lower percentage of germination of the pollen grains derived from in vitro-developed flowers, flowers induced in culture could be self-pollinated and developed seedpods with viable seeds. Nearly 90% of these seeds developed into protocorms on germination in vitro. These seedlings were grown in culture and induced to flower in vitro again using the same procedure.
在体外培养的“超普雅微笑石斛”组培苗被诱导开花，大约11个月内产生了可育种子。一种含有11.1μM苄基腺嘌呤（BA）的双层培养系统（一层由结冷胶固化，顶部覆盖一层相同体积和成分的液体培养基）在组培苗从萌发开始的6个月内诱导出最高的开花率（45%）。通过在双层培养前预先选择形态正常的幼苗，花序诱导率提高到了72%。培养中的组培苗产生了完整花（发育正常但比田间种植植物的花小）和不完整花。体外发育的完整花的花粉和雌性生殖器官在形态和解剖结构上与田间种植植物的花相似。此外，体外发育花产生的花粉粒中有65%是四分体，这表明在小孢子发生过程中发生了正常的减数分裂。在改良的克诺普培养基上培养8天，体外发育花和田间种植植物的花产生的花粉粒萌发率分别为18.2%和52.8%。尽管体外发育花产生的花粉粒萌发率较低，但培养中诱导的花可以进行自花授粉并发育出带有可育种子的荚果。这些种子中近90%在体外萌发时发育成原球茎。这些组培苗在培养中生长，然后使用相同的程序再次在体外诱导开花。
