J Integr Plant Biol. ›› 1955, Vol. 4 ›› Issue (3): -.

• Research Articles •    

On the Cultivation of Haitai (Laminaria japonica Aresch.) by Summering Young Sporophytes at Low Temperature

C. K. Tseng, K. Y. Sun & C. Y. Wu   

Abstract: Commercial cultivation of haitai (Laminaria japonica Aresch.) has been carried on at Tsingtao since 1952. Although production has been stepped up quickly in the last few years, the industry has not been advancing as rapidly as it is desired. This is due to the existence of several problems inhibiting the progress of the industry. One of these concerns with the detrimental effect of various algal growths, particularly Ectocarpus, Ulva and colonial diatoms such as Licmorphora, on the growth of the Laminaria gametophytes and the development of its sporophytes. In the haitai cultivation at Tsingtao, spore collection is effected in late October through November when surface sea water temperature has already dropped down to below 20℃. It takes from two to three weeks under good conditions, and much more time under less appropriate conditions for the completion of the growth and developmental processes from spores to sporophytes. During this period, Laminaria has the least ability of competition against algal weeds, and it is in the same period when Ectocarpus and various other algal weeds are most vigorous in their multiplication. Therefore, soon after the setting of the collectors with the Laminaria spores in the sea, spores of these weeds quickly adhere to these artificially set substrata, and before formation of the Laminaria sporophytes has been effected, these weeds have already grown to such sizes as to choke the microscopic gametophytes, prohibiting them from receiving sufficient light to satisfy their growth and developmental requirements. Thus, formation of haitai sporophytes is greatly delayed or even totally inhibited, resulting in greatly decreased production or in extreme cases, total failure of the crop. Solution of the problem has therefore become one of the keys to the further development of the haitai cultivation industry. A means to solving this problem has now been devised by collecting the spores in early summer instead of middle or late autumn, cultivating the spores and subsequently the gametophytes and the sporophytes in a temperature lower than 20~C (temperature actually employed about 10℃) during the summer, and growing the young sporophytes in the open sea soon after the surface sea water temperature drops down Lo about 20℃. By means of this change in the time of spore collecting and the cultivation of the young sporophytes in artificially lowered temperature in the summer, the sporophytes, when taken out from the cold room and cultivated in the sea in middle or late autumn, are already several millimeters in size and are able to grow much faster and more vigerously than Ectocarpus or the other algal weeds. Consequently, these weeds are unable to grow on the same collectors, or if they do so, are not able to affect the growth of the Laminaria. The method employing summering young sporophytes at low temperature not only solves the problem of the competition of various weeds, but also results in an increased production. When compared with the control experiment, the yield is a little more than double (208:100). This is due to the fact that under the special treatment, the sporophytes have two more months of growth than those cultivated by the usual method. By using the special method, laboring conditions have also been improved, since segregation of the young sporophytes could then be conducted in December and early January instead of late January and February when surface sea water temperature approaches freezing point. Moreever, costs involved in summering haitai sporophytes could also be minimized or even totally eliminated. Possibilities in commercial cultivation of haitai to the south of Tsingtao and of Undaria pinnatifida in East China coast (especially Chekiang) by employing the new method have also been suggested.

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