Irradiance, temperature, and carbon dioxide enrichment affect photosynthesis in Phalaenopsis hybrids

Abstract

The short-term effects of photosynthetic photon flux (PPF), day/night temperatures and CO2 concentration on CO2 exchange were determined for two Phalaenopsis hybrids. At 20°C, the saturating PPF for photosynthesis was 180 μmol · m-2 · s-1. At this PPF and ambient CO2 level (380 μL · L-1), a day/night temperature of 20/15°C resulted in the largest daily CO2 uptake. Higher night temperatures probably increased the respiration rate and lowered daily CO2 uptake in comparison with 20/15°C. An increase in the CO2 concentration from 380 to 950 μL · L-1 increased daily CO2 uptake by 82%.