Responses of morphological and biochemical traits of bamboo trees under elevated atmospheric O3 enrichment

Li Li (a), Jinling Li (a,b), Xiaoke Wang (c), Sami Ullah (d)* , Shuyan Lina (a)
(a) Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
(b) Guangxi Eco-engineering Vocational and Technical College, Liuzhou, Guangxi, China
(c) State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
(d) School of Geography, Earth and Environmental Sciences & Birmingham Institute of Forest Research, University of Birmingham, UK

To identify the possible mechanism of an O3 tolerant plant species- dwarf bamboo (Indocalamus decorus) in leaf morphological, antioxidant, and anatomical characteristics, we exposed three-year-old I. decorus seedlings to three O3 levels (low O3-LO, medium O3-MO and high O3–HO) over a growing season using open-top chambers. The results indicated that 1) the stomata O3 flux (Fst) of HO decreased more rapidly with time. The foliar O3 injury of HO and MO occurred when AOT40 was 26.62 ppm h and 33.20 ppm h, respectively, 2) under EO3, leaf number, leaf mass per area, leaf area, and stomata length/width all decreased, while leaf thickness, stomatal density, width, and area increased compared to the control, 3) MDA and total soluble protein contents all showed significantly increase under HO (36.57% and 32.77%) and MO (31.91% and 19.52%) while proline contents only increased under HO (33.27%). 4) MO and HO increased leaf bulliform cells numbers by 6.28% and 23.01%, respectively. HO reduced the transverse area of bulliform cells by 13.73%, and 5) the number of fusoid cells interspace, the transverse area of fusoid cells interspace, and mesophyll thickness of HO significantly increased by 11.16%, 28.58%, and 13.42%, respectively. In conclusion, the strong O3 tolerance characteristics of I. decorus stem from adaptions in the leaf’s leaf and stomatal morphological structural, antioxidant, and anatomical features. One critical attribute was the enlargement of the bulliform cell transverse area and the transverse area of fusoid cells interspace that drove this resistance to O3. Local bamboo species with high resistance to O3 pollution thus need to be promoted for sustained productivity and ecosystem services in areas with high ambient O3 pollution.