EFFECTS OF BLUE AND RED LIGHT ON STEM ELONGATION AND FLOWERING OF TOMATO SEEDLINGS

Year-round tomato cultivation needs high-quality seedlings of which stem length and node position of the first flower truss are controlled at suitable values.
The objective of this study was to develop a method for controlling stem elongation and flowering of tomato seedlings in a closed seedling production system using light emitting diodes (LEDs). To this end, we measured the growth parameters of tomato seedlings grown under a mixture of blue (B; peak wavelength, 450 nm) and red (R; peak wavelength, 660 nm) LEDs to determine the optimum light conditions.
We conducted two experiments to investigate whether the blue/red (B/R) ratio or blue and red light quantity affects morphogenesis.
In experiment 1, the stem length at a 1.0 B/R ratio was shorter than that at a 0.1 B/R ratio.
The node position of the first flower truss at the 0.1 B/R ratio was lower than that at the 1.0 B/R ratio.
The net photosynthetic rate increased upon the decrease of the B/R ratio.
Therefore, it appeared that flowering promotion was affected by photosynthesis.
In experiment 2, stem elongation under 25, 50, and 75 μmol m^-2 s^-1 of red light with a constant quantity of blue light remained similar regardless of red light quantity.
These results suggested that stem elongation depended on blue light quantity.
Thus, LED irradiation at 75 μmol m^-2 s^-1 of blue light and a B/R ratio of <1.0 would suppress spindly growth and promote flowering during tomato seedling growth.

VII International Symposium on Light in Horticultural Systems

K. Nanya, Y. Ishigami, S. Hikosaka , E. Goto

blue/red ratio, closed plant production system, LED, morphogenesis, photosynthesis

https://doi.org/10.17660/ActaHortic.2012.956.29