Enhancing Flower Stalk Emergence in Phalaenopsis by Red Light Supplementation

Abstract

A key step in regulating the flowering of Phalaenopsis is to control the emergence of the flower stalk or spiking. Light quality is an important factor to regulate plant reproduction. We used either red or blue light emitting diodes (LEDs) to substitute for 10% photosynthetic photon flux emitted by white fluorescent tubes as the control (WC) at approximately 70 μmole • m −2 • s −1 to examine the effects of enhanced red (WR) or blue (WB) light on spiking and the dawn-to-dusk fluctuations in the photosynthetic pigments and carbohydrates of Phalaenopsis aphrodite, which were grown in 7.5 cm diameter pots for six weeks. WR treatment significantly elevated the ratio of red to far-red light and the level of phytochrome photostationary state in concurrence with an increase in the spiking ratio and length, but had little effect on the concentrations of chlorophyll a and chloro-phyll b in the leaf, levels of soluble sugars such as glucose, fructose, sucrose, and insoluble starch in the leaf and shortened stem, the locus of spiking, when compared to the other two treatments. Evidently, the spiking of Phalaenopsis is improved by dependent on the relative amount of active phytochrome expressed in the photostationary state.