Abstract: Forest decline has long been attributed to air pollution and acid rain/fog, with ozone having a record for damaging trees. This study investigated eco-physiological changes on Japanese red pine caused by simultaneous fumigation of O(3) (O) and fluoranthene (F) over a 90 day period. Seedlings were exposed individually or in combinations to 10 muM fluoranthene and O(3) (3 ppm and 6 ppm in 60 days and 90 days, respectively) inside growth chambers. Eco-physiological parameters monitored included gas exchange, chlorophyll fluorescence, needle chlorophyll content, and visual appearance. After 90 days, O + F treatment showed deleterious effects on visual needle appearance and the net photosynthesis rate near saturated irradiance. In addition, decreased levels in stomatal conductance, photochemical efficiency of PS II in the dark, and total chlorophyll and Chl a: Chl b were observed. F only treatment showed similar results but in lesser magnitude compared with F + O treatment. O treatment alone showed no significant negative effect, probably due to its low concentration in the 60 day treatment. The addition of mannitol (OH radical scavenger) mitigated O + F and F negative effects. Fluoranthene deposited on Japanese red pine presents great eco-physiological damage risk, even at low O(3) concentration. Furthermore, the effects of O(3) assisted phyto-toxicity of fluoranthene on red pine may have relevance to other plant species.
Abstract: Polycyclic aromatic hydrocarbons (PAHs) have been widely studied with respect to their carcinogenic and mutagenic effects on animals and human cells. Phenanthrene (PHE) and fluoranthene (FLU) effects on the needle photosynthetic traits of 2-year-old Japanese red pine (Pinus densiflora Sieb. et. Zucc.) seedlings were investigated. Three months after fumigation of foliage with solutions containing these PAHs (10muM each), FLU had negative effects on net photosynthesis at near-saturating irradiance, stomatal conductance, initial chlorophyll fluorescence, and the contents of total chlorophyll, magnesium, and ribulose 1,5-bisphosphate carboxylase (rubisco) of current-year needles. PHE had similar negative effects to FLU but in lesser magnitude. The effects of the PAHs were mitigated by the addition of an OH-radical scavenger (mannitol) into the PAH solutions. PAHs deposited on the surface of pine needles may induce the generation of reactive oxygen species in the photosynthetic apparatus, a manner closely resembling the action of the herbicide paraquat.
Abstract: Generation of reactive oxygen intermediates (ROI) such as O(2)(-), H(2)O(2), and ()OH is known to be a major mechanism of damage in biological systems. This study investigated and compared effectiveness of scavenging ROI generated in fluoranthene (FLU) pre-fumigated Japanese red pine seedlings. Three kinds of eco-physiological assessments were used to express the impact of the different fumigants used inside the green house. Gas exchange measurements showed negative changes induced by 10muM FLU on Japanese pine seedlings during a 10d exposure period whilst no negative change was found during a 5d exposure period. Moreover, during a 14d FLU exposure incorporating ROI scavengers, results revealed that chlorophyll fluorescence, needle chemical contents and needle dry mass per unit area of the seedlings were affected. The negative effects of FLU on the conifer were dependent on both the dose and period of FLU fumigation. Peroxidase (PERO), superoxide dismutase (SOD) and mannitol (MANN) were all effective scavengers of ROI. MANN scavenged ()OH, the most lethal of the ROI. For practicable use, MANN is more economical, and may be the best ROI scavenger among the three considered. It can be concluded that efficient scavenging of ROI in biological systems is important to mitigate the negative effects of FLU on Japanese red pine trees.
Abstract: Forest decline in Japan has long been traced to air pollution and acid rain/fog, with ozone having high tree damaging records. This study investigated the eco-physiological changes brought to the evergreen conifer, Japanese red pine, by simultaneous fumigation of O3 (O) and fluoranthene (F), a four ring polycyclic aromatic hydrocarbon, in a 90 d period. Seedlings were exposed singly or combined to 10 μM fluoranthene and O3 (3 ppm h in the first 60 d, or 6 ppm h in the last 30 d period) in open top chambers. After 90 d, O+F treatment showed negative effects on the needle visual symptoms, net photosynthesis rate at near saturated irradiance, stomatal conductance,photochemical efficiency of PS II in the dark, total chlorophyll content and Chl a :Chl b ratios. F treatment showed similar results but in lesser magnitude compared with F+O treatment. O treatment alone showed no significant negative effect, probably due to its low concentration in the first two months; in most cases, its effects are same with the control. Mannitol(M) additions mitigated O+F & F negative effects. Fluoranthene deposited on needle surfaces of Japanese red pine presents greater ecological damages risk to the red pine at low O3 concentration. The ubiquitous nature of fluoranthene combined with increasing trends of O3 effects on vegetation should be a major global environmental interest.
