ラジノクローバにおける¹⁴CO₂の同化と同化産物の転流に関する実験 : 第5報 葉のageと同化および同化産物の供給能力との関係

抄録

In order to clarify the ability of assimilation and translocation at different developmental stages of leaf, the following experiments were conducted. Experiments : By exposing the leaves at different stages of developnlent, from emergence to full expansion, in the ¹⁴CO₂, the stagle when the developing leaves start to translocate their assimilates was examined. Classification of development stages after leaf emergence.to full expansion was followed by Carlson's 10 morphologic development stages.All the test plants, except a particular leaf at different development stages, were covered with aluminium foil, and ¹⁴CO₂, was fed for 1 hour. Immediately after feeding of ¹⁴CO2, aluminium foil was removed and the plants were kept in outdoor conditions. Twenty four hors after feeding of ¹⁴CO₂, the plants were harvested and radioautoglaphs were taken. Experiment 2: The ability of assinlilation, and the rates of respiration, translocation and retaining of assimilates at different ages of leaves after the full expansion stages were compared using radioisotopic techniques. Plants were fed ¹⁴CO₂ for lO min. and immediately after treatment, selected plants-one third of the total plants-were harvested and radioactivity of ¹⁴C in the leaves was counted. Half of the remaining plants was kept in the growth chamber of 20°C afer ¹⁴C assimilation. To avoid the translocation of assimlates, leaves of another half of the plants were cut at the petioles 2 cm below leaflet, and put into the glassflask, fi1led with distilled water. They were kept in the same growth chamber. Forty eight hrs. after ¹⁴CO₂ treatment, the plants were harvested and radioactivity of ¹⁴C in the leaves was counted.It is considered that : 1) radio-activityof ¹⁴CO in the leaves inlmediately after ¹⁴CO₂ feeding shows ability of assimilation, 2) ¹⁴C remaining in the leaves 48 hrs. after ¹⁴C assimilation shows the assimilates retained by the assimilating leaves themselves. 3) decrease of ¹⁴C in the detached leaves shows the amount of consumption in respiration, and 4) the amount of ¹⁴C translocated was calculated from these figures. Results of these two experiments are as follows : 1. The leaves of ladino clover are one of the strongest sinks at the early development atage. With the growth of leaves, a change occurs in the function of leaves from sink to source. When developing leaves reached about 65-70% of their maximum leaf area, they started to translocate assimilates. 2. In the case of matured leaves in general, the younger the leaves, the higher the ability of assimilation except leaf Number 1. As for the release rate in respiration, younger leaves utilize a large portion of assinmilates in respiration, and they also retain a large portion of assimilates in their leaves. Therefore, the amount of translocation of younger leaves is not so much. Consumption in respiration and retaining amount decrease in the leaves at middle age. Total amount and rate of translocation of the assimilates are the grleatest in the case of leaves at middle atage (leaves of Number 3 to 6 from growing points), followed by older leaves. 3. Middle and older leaves retain a fairly large porion (15 to 20%) of assimilates in their assimilating leaves themselves.