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wen du dui zhen jiang zuo sheng chang fa yu de ying xiang
Pages: 283-293
Year: Issue:  4
Journal: Oceanologia et Limnologia Sinica

Keyword:  不同温度生长发育日生长海水温度生长速度江篱藻体生长雄配子体盘状体真江蓠;
Abstract: Apical fragments cut from tetrasporophyte or carposporophyte of the same frond. The old plants survived after wintering and single young sporelings were used in this experiment. These materials were collected at different times at Zhanshan Bight, Qingdao in 1980 and 1982 and culture,d under different temperature conditions(5, 10, 15, 20, 25, and 30℃). The light was supplied by three 40W fluorescent tubes, 2600—3700lx, for 10 hours per day. The culture medium was enriched with 0.001mol/L KNO_3 and 0.0001mol/L KH_2PO_4 in sterile seawater. The results of the experiments are summarized as follows. 1. The effect of temperature on growth was different for tetrasporophyte and carposporophyte. The results of observations on apical fragments in different temperatures showed that tetrasporophyte grows more favorably at 25℃ and carposporophyte grows fast at 15℃. The fronds of this two plants showed no growth at 30℃, and fell into decay when the culture duration was longer under this experiment condition. The growth of Gracilaria asiatca appeared very slow at 5℃ and the plant will lost most parts of the frond when the temperature went below 5℃ in the field during winter. Therefore the lower limit of the temperature for the growth of Gracilaria asiatica should be 5℃. From a study of the growth of old plants and single young sporelings under different temperatures, the favorable temperature for the growth of Gracilaria asiatica should be between 15℃ and 20℃. At the young sporeling stage it might be raised to 25℃C. The temperature range for the maturation of Gracilaria asiatica is between 10—25℃. Tetrasporophyte and Carposporophyte can not form the sporangia when the temperature is beyond this range. 2. During the course of the growth of Gracilaria many lateral branches of the frond appear as the plant grows in length. The wet weight increase of the plant is more characteristics than the length increase. 3. The results obtained from this experiment, show that the old plants that survive the winter can regenerate new branches, and that the sporelings that develope from the old disc and the erects that project from the new disc can grow up when the temperature is favorable. Therefore, there are three different ways for Gracilaria to develop into new plants in spring: by the regeneration of the old plants, by the development of sporelings from old discs, and the projection of new erects from new discs. Among these three different ways the development of sporelings from old discs is the main way, since their growth rate is three times that of the old plants. The percentage of new discs germinated from tetraspores and carpospores is low. In a nature population of Gracilaria, the erects projected from new discs supplement the deficiency that resulted from the decay of the old plants. This alternate way of developing new plants keeps the natural population of Gracilaria constant. 4. Under the same temperature condition, the growth rate of the fronds of the old plants appears different. Our experiment shows that Gracilaria is a perennial plant with two growth periods(one from spring to early summer, one in antumn). When the temperature is over 25℃ in summer and below 5℃ in winter, the plants lose most parts of their fronds. At low tide, however, the plants can keep most of their fronds from decay in summer and keep growing till early winter. Plants of different ages can be collected at the same time, thus proving their growth rates are different.
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