摘要
我们研究了不同温度对龙须菜果孢子萌发体生长的影响,发现25℃为萌发体的生长最适温度。此外,果孢子在35℃下仍能萌发及生长成盘状体,这表明在龙须菜的二年生的生长周期中,其幼株是起了抗高温的作用。自然生态方面的研究证明了这个推论。在湛江地区,水温最高的季节为7—9月份,该时,龙须菜的成长藻体已完全消失,但在自然海区仍可发现有长约1厘米左右的幼株存在。在湛江及其附近,自然海区中所出现的龙须菜的幼苗群落以4—6月份为最多。7—9月份则显著地减少,该时,藻体的营养生长几乎完全受到抑制。这些受抑制的幼株以后随着水温的降低而又能重新生长,并形成10月及11月初所见的幼株群落。这些幼株在冬季及翌年春旺盛地生长,长成长大的藻体。根据上述的试验及观察,我们认为人工采苗的季节可在3、4月份龙须菜的收获季节中进行,利用幼苗渡夏,集中管理,争取在水温降低时早日分散放养。在有条件的地区,可以考虑室内适温(20—25℃)育苗。从野外观察及人工割切试验,证明龙须菜藻体具有显著的再生能力。根据我们的初步割切试验(见表6),藻体的再生长速率为每日0.6厘米。因此,生产上可以考虑充分利用这种能力以得到一年较多次的收获。
Carpospore-germlings of the marine alga Gracilariopsis sjstedtii (Kylin) Daw- son cultured at different temperatures in enriched sea water showed a maximum rate of growth at 25℃ (Tables 1--5, Fig.2). In addition, the germlings demonst- rated a marked ability to withstand temperature as high as 35℃. This distinct behaviour indicates that the sporelings of this species play an important role in with standing the high-temperature months in the biennial cycle of vegetative growth. Ecological observations confirm our assumption. According to our survey data, plant- lets about 1 cm in height do exist in the natural habitat at Zhan-jiang from July to September when the larger thalli are completely damaged. The most luxurious population of the sporelings appeared in April, May and June with an apparent diminution in the hottest months (from July through Septem- ber). At that time of the year, the vegetative growth almost entirely stopped. These dormancy-like plantets, however, grew anew and formed the plantlets of October and early November as the water temperature declines. They grew vigorously throughout the winter and attained the tallest growth in the following spring. Cutting experiments for the wild plant have been carried out in the field. The average growth rate obtained for the generative thalli (Table 6) was found to be 0.6 cm per day.
