Acute NO2 Stress Shortens the Median Survival Period of Bougainvillea glabra ‘Elizabeth Angus’ by Disrupting Tissue Structure and Photosynthetic Response Centers

Abstract

The air pollutant NO2 is one of the major constraints on plant growth, and the ecological value of the ornamental plant Bougainvillea glabra can be weakened by NO2. In this study, an indoor 4 μL·L−1 NO2 simulated fumigation test was conducted with three treatments, CK (normal growth with clean air), T1 (4 μL·L−1 NO2 + 8 h/d), and T2 (4 μL·L−1 NO2 + 24 h/d), which were set up with considerations for time and concentration. The results demonstrated that most of the morphological parameters of B. glabra ‘Elizabeth Angus’, except for the floral organs, were decreased in the root, stem, leaf, and bract. Continuous fumigation significantly attenuated the growth rate and reduced the water and pigment contents of organs. Excessive NO2 reduced the number and transfer rate of photoelectrons by destroying the photosynthetic reaction center, which in turn weakened photosynthesis, but the plants with intermittent fumigation recovered after fumigation. The Kaplan-Meier (K-M) survival curve displayed median survival periods of 41 and 55.5 h for T1 and T2, respectively, and the morphological structure and most of the indicators of photosynthetic reaction centers changed significantly during stress. Acute injury to B. glabra ‘Elizabeth Angus’ was caused by 4 μL·L−1 NO2, and B. glabra ‘Elizabeth Angus’ had limited ability to regulate high concentrations of NO2 acute stress.