Effects of elevated carbon dioxide and/or ozone on endogenous plant hormones in the leaves of Ginkgo biloba

Abstract

Four-year-old Gingko (Ginkgo biloba L.) trees were exposed to ambient and elevated concentrations of CO2 and O3, and their combination for 1 year, using open-top chambers in Shenyang, China in 2006. Growth parameters and endogenous plant hormones were measured simultaneously over the experiment period. Elevated CO2 increased leaf area and leaf dry weight but had no effect on shoot length, increased indole-3-acetic acid (IAA), gibberellins A3 (GA3), zeatin riboside (ZR), dihydrozeatin (DHZR) and isopentenyl-adenosine (iPA) content but decreased abscisic acid (ABA) content. Elevated O3 significantly decreased leaf area, leaf dry weight, shoot length, and decreased IAA, GA3, ZR content but increased ABA content and had a little effect on iPA, DHZR content. Elevated CO2 + O3 decreased IAA, iPA and DHZR content while increased ABA and GA3 content in the early stage of the exposure and then decreased in the late stage. The evidence from this study indicates that elevated CO2 ameliorated the effects of elevated ozone on tree growth, and elevated CO2 may have a largely positive impact on forest tree growth while elevated O3 will likely have a negative impact.