^<14>C-同化産物の転流からみたトウモロコシの主稈と分げつとの関係

抄録

The following experiments were conducted to evaluate the relation between main shoot and tillers in corn plants. Sweet corn plants (var. Golden Cross Bantam) were grown under the wide-space planting condition (1 plant/hill, 100 cm×100 cm) in the field. Either leaf blades on the main shoot or on the tiller were allowed to assimilate ¹⁴CO₂ for 15 min. at the three growing stages. Plants were harvested 3 days after feeding and radioactivities in various plant parts were determined to reveal translocation rates and distribution patterns of ¹⁴C-assimilates. In order to assess the flexibility of source (leaf)-sink (ear shoot) relation, tillers or ears on the main shoot were removed at the stage of grain-filling. These plants were fed ¹⁴CO₂ 7 days after the removal, and were weighed 21 days after that treatment, separating into stalk and ear shoot. The results are summerized as follows: (1) At the stage before stalk elongation, translocation rate was low with 47% in the leaf blades on main shoot and 37% in the leaf blades on tiller. Some assimilates were translocated from the main shoot to tiller or conversely. The translocatcd ¹⁴C from the main shoot was found much in younger tiller and those from tiller in main root. (2) When plants were fed ¹⁴CO₂ at the stage of silking or just before, only 4% of ¹⁴C exported from the fed leaf blades was translocated into the other unfed shoots. Source activity was not yet fully shown in this stage, since translocation rate was 74% in the leaf blades on the main shoot and 58% in the leaf blades on 2nd tiller. (3) At the stage of grain filling little translocation occurred from the main shoot to tillers and from 2nd tiller bearing ears to the main shoot or the other tillers. When the tiller (5th tiller) had completed the vegetative growth and yet had no ear, however, it translocated 70% of exported ¹⁴C from its leaf blades into the main shoot, constituting the main source for development of 2nd car on the main shoot. Translocation rate of the main shoot, 2nd tiller and 5th tiller reached 85, 85 and 83%, respectively. (4) In the plants with excessive sink or source as results of tiller of ear removal, source-sink relations for ¹⁴C-assimilates were fundamentally the same as in the intact plants described above, until 7 days after the removal. Translocation rates in these plants changed little also. (5) However, while in such plants as remained only 2nd tiller bearing ears, the weight of ears on 2nd tiller was decreased after the 21 days, the weight of 1st and 2nd ears on main shoot was not changed. It shows that even the tiller bearing ears might contribute to filling of ears on the main shoot.