The influence of metal halide and high-pressure sodium lamps during photoperiod extension on the allocation of carbon between lignin and cellulose in black spruce seedlings

Abstract

Containerized black spruce seedlings (Piceamariana (Mill.) B.S.P.) were grown at the greenhouse at CIP Inc., Harrington, Québec, from February until May, 1987. We wished to test whether differences in the quantity and quality of light received from two commercially available lamps during photoperiod extension would alter the allocation of carbon between lignin and cellulose in shoots and roots. Photoperiods were extended from 17:00 to 01:00 using either metal halide and high-pressure sodium lamps together or high-pressure sodium lamps alone. At night, the treatment using both types of lamp together increased the photon flux density of blue light (400–500 nm) at seedling height 10-fold, from 0.32 to 3.2 μE m−2 s−1. Photosynthetically active radiation was increased 4-fold, from 4.5 to 17.9 μE m−2 s−1. Total seedling biomass did not differ statistically between light treatments at any given time. However, seedling biomass averaged over all times was statistically higher (p ≤ 0.03) for seedlings in the treatment using both types of lamp together. Percent lignin, percent cellulose, and lignin to cellulose ratios were not significantly affected by the light source used during photoperiod extension. As expected, percent lignin and percent cellulose in shoots and roots increased significantly with time. The percentage of seedlings judged unacceptable because of spiralized stems was not affected by light source and averaged 21.9%.