Influence of light intensity on the rate of photosynthesis and dry matter accumulation in Oriental hybrid lily ‘Siberia’ at different developmental stages

We investigated the effects of light intensity on various photosynthetic characteristics on a whole-plant (WP) basis, focussing on three developmental stages from leafing (when young leaves unfolded) to flowering in the Oriental hybrid lily 'Siberia'. On a WP basis, the net photosynthetic rate (Pr) was low at the leafing stage, but increased rapidly at the visible flower bud and flowering stages. However, on a leaf area (LA) basis, plants at the leafing stage exhibited a high Pr, peaking at the visible flower bud stage and diminishing slightly at the flowering stage. The rapid increase in total LA due to plant growth and development had a strong influence on Pr on a WP basis. 'Siberia' plants were grown under various reduced levels of natural light (0%, 40%, or 60%), achieved by shading, to evaluate the contribution of photosynthetic assimilates at various developmental stages and to compare the consistency of these results with the photosynthetic characteristics of the plants. The final dry matter (DM) content on a WP basis was determined by the light intensity applied after the visible flower bud stage, but not before. These experiments indicated that, during the growth of 'Siberia' lily, photosynthesis determined DM accumulation after the visible flower bud stage. Low or high light intensities before or after this stage promoted stem elongation and leaf thickening, respectively. Therefore, shading during the early developmental stages and high sunlight during the later developmental stages were beneficial for the quality of Oriental hybrid lily cut flowers.