Ontogeny affects response of northern red oak seedlings to elevated CO₂ and water stress: I. Carbon assimilation and biomass production

Abstract

The interactive influences of elevated carbon dioxide, water stress, and ontogeny on carbon assimilation and biomass production were investigated in northern red oak, a species having episodic shoot growth characteristics. Seedlings were grown from acorns through three shoot-growth flushes (8-11 wk) in controlled-environment chambers at 400, 530 or 700 µmol mol −" CO # and under well watered or water-stressed soil-moisture regimes. Increasing CO # growth concentration from 400 to 700 µmol mol −" resulted in a 34 % increase in net assimilation rate (A), a 31 % decrease in stomatal conductance to water vapour (g s ) and a 141 % increase in water use efficiency (WUE) in well watered seedlings. In contrast, water-stressed seedlings grown at 700 µmol mol −" CO # demonstrated a 69 % increase in A, a 23 % decrease in g s , and a 104 % increase in WUE. However, physiological responses to increased CO # and water stress were strongly modified by ontogeny. During active third-flush shoot growth, A in first-flush and second-flush foliage of water-stressed seedlings increased relative to the quiescent phase following cessation of second-flush growth by an average of 115 % ; g s increased by an average of 74 %. In contrast, neither A nor g s in comparable foliage of well watered seedlings changed in response to active third-flush growth. Whereas seedling growth was continuous through three flushes in well watered seedlings, growth of water-stressed seedlings was minimal following the leaf-expansion stage of the third flush. Through three growth flushes total seedling biomass and biomass allocation to root, shoot and foliage components were very similar in water-stressed seedlings grown at 700 µmol mol −" CO # and well watered seedlings grown at 400 µmol mol −" CO # . Enhancement effects of elevated CO # on seedling carbon (C) assimilation and biomass production may offset the negative impact of moderate water stress and are likely to be determined by ontogeny and stress impacts on carbon sink demand.

Growth pattern and photosynthetic activity of different bamboo species growing in the Botanical Garden of Rome

“…Whole culm photosynthetic rate (WNP, mmol CO 2 s À1 ) was estimated by multiplying total leaf area per culm and mean maximum yearly assimilation rate, assuming similar assimilation rates among leaves in a culm, and fully expanded leaves meet this assumption (Anderson and Tomlinson, 1998;Handson et al, 1988). The total yearly carbon sequestration capacity (kg CO 2 year À1 ) was calculated multiplying WNP by the total photosynthetic activity hours in the year (PTYH, h) (Gratani and Varone, 2006).…”

Elevated CO₂ mitigates the adverse effects of drought on daytime net ecosystem CO₂ exchange and photosynthesis in a Florida scrub-oak ecosystem

“…The interactive effects of drought and rising C a are considered crucial for the prediction of the responses of forest trees to the global environmental change (Beerling et al 1996, Norby andLuo 2004). Many studies on the responses of trees to elevated C a (EC) under water stress have been reported (Morison 1993, Dixon et al 1995, Roden and Ball 1996, Anderson and Tomlinson 1998, but most of these studies were carried out with seedlings under controlled environment and only relatively short-term C a enrichment. There are several differences in the field compared to controlled environment regarding drought: (a) Drought stress evolves more gradually in the field and plants experience no root constriction from confinement in pots (Lawlor and Mitchell 1991, Ceulemans and Mousseau 1994, Körner 1995.…”

Modelling of the relationship between the SPAD values and photosynthetic pigments content in Quercus petraea and Prunus serotina leaves

“…Low Chl content can limit the potential of photosynthesis, thereby reducing the primary production of organic compounds (Niyogi 1999;Valladares et al 2002). In ecophysiological studies quantity of Chl reflects responses of plants to different stressors such as: nitrogen deficit (van den Berg and Perkins 2004, Zhao et al 2005, Percival et al 2008, drought (Anderson and Tomlinson 1998;Peñuelas and Filella 1998;Schlemmer et al 2005) or high irradiance (Merzlyak and Gitelson 1995;Valladares et al 2002;Adams et al 2004, Main et al 2011. Carotenoids (Car) play a role of "screening pigments" protecting the photosynthetic apparatus against excess energy and their high content in leaf may indicate a photoinhibitory stress (Demmig- Adams et al 1989;Adams and Demmig-Adams 1994;Niyogi 1999).…”