title: Effect of Low pH and Aluminum Toxicity on the Photosynthetic Characteristics of Different Fast-Growing Eucalyptus Vegetatively Propagated Clones.
abstract: Knowing how acid soils and aluminum in soils may limit the growth of Eucalyptus trees in plantations is important because these plantations grow in many tropical and subtropical regions. Seedlings of four vegetatively propagated Eucalyptus clones, E. grandis × E. urophylla 'GLGU9'(G9), E. grandis × E. urophylla 'GLGU12' (G12), E. urophylla × E. camaldulensis 'GLUC3' (G3) and E. urophylla 'GLU4'(G4), were subjected to liquid culture with Hoagland nutrient solution for 40 days, then treated with four different treatments of acid and aluminum for 1 day. The four treatments used either pH 3.0 or 4.0 with or without added aluminum (4.4 mM) in all possible combinations; a control used no added aluminum at pH 4.8. Subsequently, the photosynthetic parameters and morphology of leaves from eucalypt seedlings were determined and observed. The results showed that the tested chlorophyll content, net photosynthetic rate, transpiration rate and water use efficiency were apparently inhibited by aluminum. Under uniform Al concentration (4.4 mM), the Al-induced limitation to photosynthetic parameters increased with pH, indicating acid stimulation to Al toxicity. Among all treatments, the most significant reduction was found in the combination of pH 3.0 and 4.4 mM Al. The photosynthetic and transpiration rates showed similar trends with G9 > G12 > G3 > G4, suggesting that G9 and G12 had higher Al-tolerance than other two clones. Microscopic observation revealed changes in leaf morphology when exposed to Al stress; for example, a reduced thickness of leaf epidermis and palisade tissue, the descendant palisade tissue/spongy tissue ratio and leaf tissue looseness. Overall, the acid and aluminum stress exerted negative effects on the photosynthetic activity of eucalypt seedlings, but the differences in tolerance to Al toxicity between the clones were favorable, offering potential to improve Eucalyptus plantation productivity by selecting Al tolerant clones.
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China; Key Lab of National Forestry Bureau for Fast-growing Wood Breeding in Central South China, Guangxi University, Nanning, Guangxi, China; Guangxi Colleges and Universities Key Laboratory of Forestry Science and Engineering, Nanning, Guangxi, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China; Key Lab of National Forestry Bureau for Fast-growing Wood Breeding in Central South China, Guangxi University, Nanning, Guangxi, China; Guangxi Colleges and Universities Key Laboratory of Forestry Science and Engineering, Nanning, Guangxi, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Tan
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China.
authors.forename: Yihui
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Cheng
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China; Key Lab of National Forestry Bureau for Fast-growing Wood Breeding in Central South China, Guangxi University, Nanning, Guangxi, China; Guangxi Colleges and Universities Key Laboratory of Forestry Science and Engineering, Nanning, Guangxi, China.
authors.forename: Shaoming
authors.initials: S
authors.lastname: Ye
authors.affiliation: Forestry College, Guangxi University, Nanning, Guangxi, China.
authors.forename: Weixin
authors.initials: W
authors.lastname: Jiang
mesh_terms: D000535:Aluminum / Q000633:toxicity*; D002734:Chlorophyll / Q000378:metabolism; D005052:Eucalyptus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008853:Microscopy; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D014867:Water / Q000378:metabolism
chemical_list: D012987:Soil; D014867:Water; D002734:Chlorophyll; D000535:Aluminum