Effect of low irradiance on the photosynthetic performance and spiking of Phalaenopsis

Abstract

Lowering irradiance can delay the flower stalk, i.e., spike development, in order to schedule flowering time of Phalaenopsis; however, the effect on photosynthetic performance and spiking inhibition remains poorly understood. We compared light and shade treatments of Phalaenopsis aphrodite subsp. formosana in order to determine how limiting light affects day-night changes in the photosynthetic capacity of leaves and the carbon pool of leaves and stems resulting in delayed spiking. The low irradiance treatment [20 μmol(photon) m ] for six weeks did not affect potential functions of photosynthetic apparatus estimated by chlorophyll a fluorescence analysis, but it significantly reduced the net CO 2 uptake and O 2 evolution rates, carbohydrate and organic acid concentrations, and amplitudes of CAM activity in new and fully expanded leaves of Phalaenopsis and delayed the spiking compared with the control kept at 150 μmol(photon) m 2 s 1. The shortened stem contained a remarkably high sucrose concentration, accounting for more than 80% of total soluble sugars for both treatments throughout the day. Moreover, the sucrose concentration was unaffected by the lowering of irradiance. The relationship between the sucrose content and spiking seemed to be loose; the major factor(s) for spiking in Phalaenopsis remained to be ascertained as the flower stalk bud is attached to the shortened stem.

Evaluation of Carbohydrate Concentrations in Phalaenopsis Using Near-infrared Spectroscopy

“…In the greenhouse plants, the concentrations of fructose, glucose, and starch remained at higher levels of %2% of DW, and the sucrose concentration stayed at 1% of DW (Table 1). The levels of fructose, glucose, sucrose, and starch in the shoots and roots of dark-treated plants were approximately consistent with the results reported by previous studies (Hou et al, 2011;Liu et al, 2016). The NIR spectra of the 302 Phalaenopsis samples (126 leaves, 88 shoots, and 88 roots) were obtained using MSC treatment.…”

Performance Index and PSII Connectivity Under Drought and Contrasting Light Regimes in the CAM Orchid Phalaenopsis

“…Chlorophyll fluorescence measurements in CAM plants mainly report photochemical and non-photochemical quenching (qP and qN), the maximum quantum efficiency (F v /F m ) and the effective quantum yield ( Φ PSII ) of PSII photochemistry (Table 1; Winter and Demmig, 1987; Winter et al, 1990; Keiller et al, 1994; Adams and Demmig-Adams, 1996; Heber et al, 1996; Barker and Adams, 1997; Skillman and Winter, 1997; de Mattos et al, 1999; Lin and Hsu, 2004; Masrahi et al, 2015; Liu et al, 2016; Arias-Moreno et al, 2017). A detailed investigation of the performance index, specific energy fluxes related to PSII processing and the concept of connectivity between PSII units (Figure 1 and Table 1) revealed important PSII related adaptations concerning the initial light reactions in CAM plants under different environmental conditions.…”

Analysis effect of shade level on the physiological and anatomical characteristics of hybrid Phalaenopsis orchid at the acclimatization stage

“…Chlorophyll a, total chlorophyll and carotenoid pigments decreased at 70% shading (Table 1), which was caused by inefficient light capture because plants were not yet adapted. Generally, plants adapted by increasing chlorophyll pigments in low light conditions (Liu et al, 2016). Low shading had a short wavelength of light that could inhibit light capture.…”