The response system of the growth, physiological and uptake characteristics of Pinus bungeana under ozone stress

Objective: To study the changes of growth, physiological and absorption characteristics of Pinus bungeana under ozone (O3) stress, to elucidate the correlations among the indicators, and to determine its degree of response to O3. Methods: The growth, physiological characteristics and O3 uptake capacity of Pinus bungeana seedlings were measured in an open-top O3 fumigation manual control experiment with three concentration gradients (NF: normal atmospheric O3 concentration, NF40: normal atmospheric O3 concentration plus 40 nmlol/mol; NF80: normal atmospheric O3 concentration plus 80 nmol/mol), and the relationships between the characteristics of Pinus bungeana under different O3 concentrations were investigated with correlation analysis, redundancy analysis and analysis of variance. Results: (1) Plant height growth (ΔH), diameter growth at 50 cm (ΔDBH), stomatal size (S), stomatal density (M), stomatal opening (K), stomatal conductance (Gs), net photosynthetic rate (Pn), transpiration rate (Et), water use efficiency (WUE), maximum photochemical efficiency (Fv/Fm), chlorophyll content (CHL), whole tree water consumption (W), and O3 uptake rate () all decreased with the increase of O3 concentration; while intercellular CO2 concentration () and relative conductivity (L) increased with the increase of O3 concentration; (2) growth indicators of Pinus bungeana under O3 stress (ΔH, ΔDBH) were the most correlated with O3 uptake status (, W), followed by photosynthetic indicators (, WUE, ,, ) and growth indicators (ΔH, ΔDBH) and stomatal characteristics (K, M, S) under O3 stress, some physiological indicators (L, ) were relatively weakly correlated with photosynthesis (, WUE,,, ) and stomatal (K, M, S); (3) all the indicators of Pinus bungeana were significantly different under O3 treatments of NF and NF80 (P < 0.05), ΔH, ΔDBH, M, CHL, , , W and were most significantly different under NF and NF40 treatments, and K, S, WUE, , , , L were more significantly different under NF40 and NF80 treatments. Conclusion: The experiment proved that the growth of Pinus bungeana was slowed, photosynthetic capacity was reduced, and the absorption capacity of O3 was further reduced by long-term exposure to high concentration of O3. The growth of Pinus bungeana was most correlated with the changes of O3 absorption characteristics, and the stomatal characteristics were most correlated with photosynthetic physiological characteristics, and the reduction of photosynthetic capacity etc. further led to the curtailment of its growth.