紫萍营养繁殖过程的解剖观察

Anatomical Studies on Turion-mediated Reproduction in Spirodela polyrhiza

以采自海南陵水的紫萍(Spirodela polyrhiza DW2501-4)为材料,观察紫萍的营养繁殖过程。紫萍DW2501-4培养在0.5倍Hoagland′s液体培养基中,先不断长出新的叶状体,随着营养物质的减少,长出休眠体进入休眠状态。休眠体经过4℃处理7 d后,可在含1%蔗糖的Hoagland′s固体培养基中重新萌发。为了进一步观察叶状体、类休眠体和休眠体的组织结构差异,以及休眠体萌发过程中组织结构的变化,制作了石蜡切片。观察结果显示:紫萍叶状体有数条叶脉,细胞中含少量的淀粉粒,表皮层以下有分层的气室,通常分上下两层,上层气室比下层气室小。类休眠体也有数条叶脉和少量气室,细胞中有较多淀粉粒。休眠体的细胞差异不明显,几乎没有气室,细胞内有大量的淀粉粒,部分细胞含有单宁;随着休眠体萌发,细胞中淀粉粒不断变小,同时分生组织分化出根和新的叶状体。

Spirodela polyrhiza strain DW2501-4 collected from Lingshui, Hainan was used to study turion- mediated reproduction. Results showed that new fronds reproduced continually in half-strength Hoagland＇s solution until nutrition was scarce. Dormant organ called turion was then formed. The turions were collected and cold-treated for one week at 4 ~C, and were transfered into half-strength Hoagland＇s solid medium with 1% sucrose, and incubated at 24 ~C. The turions germinated in 3 days. Paraffin sections of the fronds, turi- on-like fronds, and turions were prepared to observe their anatomical structures. Results indicated that fronds had several veins and a small amount of starch grains in the cells, and were full of air chambers. The air chambers in the upper layer were small while the air chambers in the bottom layer were big. Turion-like fronds contained a few veins and some small air chambers, and a lot of starch grains in their cells. Veins and air chambers were not observed in turions. A lot of starch grains were observed in turion cells, and some cells were observed to contain high level of tannin. During germination of turion, the starch grains were di- gested and became smaller and smaller, and roots and new fronds were formed.