Varietal Difference in Growth and Translocation of ¹⁴C-Assimilates in Carnations Grown at Different Night Temperatures

Abstract

Comparative studies were made between two carnation cvs. Scania and Coral, on the translocation of photosynthates for 24 hours after feeding ¹⁴CO₂ in day time.
Eight plants of each cultivar in plastic pots were grown in a greenhouse until the flowering period, and then taken into two growth chambers controlled at 10°C (N 10) or 15°C (N 15) in the dark (14 h-day and 10 h-night, 20°C in the day) and kept growing for 40 days from October 1 to November 9.
The selected two plants of each cultivar in each growth chamber, namely 8 plants, were put in an assimilation chamber in an isotope-greenhouse and fed with 200μCi ¹⁴CO₂ for one hour from 1.00 to 2.00 p.m. The plants were taken out immediately (A plot) and 24 hours (B plot) after trapping the residual ¹⁴CO₂ in the chamber with 1N KOH and NaOH solutions for one hour, respectively.
Growth of cv. Scania, namely: stem length, number of leaves and cut flowers, at N 15 was superior to that at N 10. Cv. Coral showed a more significant growth at N 10 than N 15.
In cv. Scania grown at N 10, ¹⁴C-radioactivity was relatively high in leaves attached to both the primary and secondary branches in A plot, and was highly increased in the terminal and lateral buds of the secondary branches in B plot. In those treated at N 15, the activity was significantly high even in A plot, as well as in B plot.
In cv. Coral, irrespective of the thermal treatment, the radioactivity was similarly high in both the terminal and lateral buds on the secondary branches in A plot, with a slight increase in those buds in B plot.
In cv. Scania grown at N 15, the percentage of ¹⁴C-radioactivity of the secondary branches to the total of the whole plant was as high as about 70% for both A and B plots. In cv. Coral at N 10, the percentage was relatively high, being about 60% for A plot and 75% for B plot. In the case of N 15, similar results were obtained.