光同化产物在裙带菜（Undaria pinnatifida）中的运转

本文报告了用１４Ｃ标记的光同化产物在裙带菜［Ｕｎｄａｒｉａｐｉｎｎａｔｉｆｉｄａ（Ｈａｒｙ．）Ｓｕｒ］孢子体中的运转现象。观察到光同化产物约需２０ｍｉｎ才能从叶片表皮进入中肋的髓部。在自然条件下，光同化产物主要自叶片梢部经中肋向生长部运转，在叶片梢部和生长部之间存在明显的源一库关系。运转速度约为４２～４８ｃｍ／ｈ。用组织放射自显影的方法证实了髓部的喇叭丝是主要的运转组织。向下运转的溶于酒精的光同化产物中，甘露醇占５０％以上。还在光同化产物中观察到游离的谷氨酸、天门冬氨酸和丙氨酸。

Translocation of Photosguthates in Undaria pinnatifida

Translocation of 14 C-labelled photosynthates in rapidly growing sporophyte of Undaria pinnatifida was studied in the open sea. Analysis of the samples from different parts of the blade and the counterparts exposed to tracer (NaH14 CO3 ) showed that translocation occurred mainly from the tip of the blade to the growing region with an apparent source--sink relationship. It took 20 min to translocate thelabelled photosynthates from the epidermis, via cortex, to the medulla of the midrib. In the midrib, rates of translocation averaging 42 -- 48 cm/h were observed in the open sea. After being freeze--sectioned and freezedried, the samples were used in the study on the pathway of translocation in the midrib by autoradiographic method. It was found that most photosynthates were confined to trumpetshaped cells in medulla. These data indicate that the conduction of photosynthates tukes place in the medulla and trumpet-shaped cells are the main conducting elements. Of the alcohol-soluble photosynthates translocated downward, more than 50% was found to be mannitol. Free amino acids such as Gln, Asp and Ala were also found in the 14 C--labelled photosynthates.