Changes in root growth and relationships between plant organs and root hydraulic traits in American elm (Ulmus americana L.) and red oak (Quercus rubra L.) seedlings due to elevated CO2 level

Abstract

The relationships between plant organs and root hydrological traits are not well known and the question arises whether elevated CO 2 changes these relationships. This study attempted to answer this question. A pseudo-replicated experiment was conducted with two times 24 American elm (Ulmus americana L.) and 23 and 24 red oak (Quercus rubra L.) seedlings growing in ambient CO 2 (around 360 μmol·L -1 ) and 540 ± 7.95 μmol·L -1 CO 2 in a greenhouse. After 71 days of treatment for American elm and 77 days for red oak, 14 American elm and 12 red oak seedlings from each of the two CO 2 levels were randomly selected in order to examine the flow rate of root xylem sap, root hydraulic conductance, total root hydraulic conductivity, fine root and coarse root hydraulic conductivity. All seedlings were harvested to investigate total plant biomass, stem biomass and leaf biomass, leaf area, height, basal diameter, total root biomass, coarse root biomass and fine root biomass. The following conclusions are reached: 1) plant organs respond to the elevated CO 2 level earlier than hydraulic traits of roots and may gradually lead to changes in hydraulic traits; 2) plant organs have different relationships with hydraulic traits of roots and elevated CO 2 changes these relationships; the changes may be of importance for plants as means to acclimatize to changing environments; 3) biomass of coarse roots increased rather more than that of fine roots; 4) Lorentzian and Caussian models are better in estimating the biomass of seedlings than single-variable models.

Increased atmospheric carbon dioxide concentration: effects on eucalypt rust (Puccinia psidii), C:N ratio and essential oils in eucalypt clonal plantlets

“…The results obtained in the present study in OTCs and CCs demonstrated that increased atmospheric CO 2 reduced the severity of rust, increased plant growth and did not alter the concentration of essential oils in eucalypt plantlets (Figs 1-3). Increased plant growth as a result of increased CO 2 concentrations has been demonstrated in various species and is related to increased photosynthesis and other metabolic processes (Duff et al 1994;Pangga et al 2004;Cheng 2009;Runion et al 2010;Niu et al 2011). Few studies have evaluated the changes in the severity of diseases and pathogen life cycles resulting from increased atmospheric CO 2 concentrations (Eastburn et al 2011).…”