Studies on the Assimilation and Translocation of 14CO2 in Ladino Clover

[摘要] Three series of experiments were conducted in a hope of elucidating which leaves of ladino clover are most active in assimilation and contributing most to the matter production, in what speed the assimilated substances move in the plant, in which parts they are accumulated, and what is the relationship between the leaf order and the direction of the translocation of the assimilates. 1) The whole plants were treated for 41/2 hours with 14CO2, immediately followed by 10 sec. of boiling water treatment, and the radioautographs were taken. 14C activity in every leaf of the plant was fairly high, but the younger the leaves, the higher was the activity, showing the difference in assimilating ability. 14C was seen at the end of treatment already translocated in the roots. Strong accumulation was found at nodules and root tips (Fig. 2-A). After 4 days, it was seen largely accumulated at the growing points, lateral buds and roots, while the three or four youngest leaves kept high activity of 14C, the rest showing decreasing activity from that of immediately after the treatment (Fig. 2-B), (Table 1). This is considered to be due to the consumption by respiration and the translocation to other parts of the plant. 2) Single leaves (Leaf No. 5 from growing point) of 5 plants were treated for 2 hours. Even upon the completion of treatment 14C was distributed widely in the plant, though in slight amount. In the roots and growing points, it was seen rather highly concentrated. After a day, it was, distributed all over the plant, fairly intensely at the growing points, lateral buds and roots, and especially intensely in root tips and nodules (Fig. 4-B). After 5 days a large accumulation was seen in the newly-opened leaves on the main stem and the leaves on the lateral buds which were observed as developing at the time of treatment (Fig. 4-C). This accumulation remained the same on 15th day and 47th day, the leaves newly-developed after treatment having but a weak activity of 14C. Similar fact was shown in the roots. After 1-5 days, the accumulation was strong at root tips. On 15 th and 47 th day the old parts which are identified to be the root tips at the time of treatment retained the strongest accumulation, while the newly-developed parts had only a small amount of 14C (Fig. 4-D∼E). These facts lead us to the consideration that the assimilates are consumed for the composition of the structure of the growing parts, and its retranslocation from there does not appear too much. 3) The newest leaf immediately after opening (Leaf No. 1) was treated with 14CO2. The assimilation was seen vigorous, and the translocation active. The accumulation was observed in the roots, growing points and lateral buds. Further some translocation was seen into the old leaves (Fig. 5-A). All this shows that in ladino clover the newly-opened leaf acts not as an accepter but a supplier of photosynthetic products. The leaves numbered 4-8 were active in assimilation and in supplying the assimilates into all parts of the plant, just like Leaf No. 1 (Fig. 5-B∼C). In Leaf No. 11, the ability of assimilation was smaller and the translocation was mainly basipetal and 14C was translocated not so much into the growing points on the main stem as into the lateral buds and roots in the plant base (Fig. 5-D∼E).

[学科分类] 农业科学（综合）