Rising temperature may negate the stimulatory effect of rising CO2 on growth and physiology of Wollemi pine (Wollemia nobilis)

Abstract

Rising atmospheric [CO2] is associated with increased air temperature, and this warming may drive many rare plant species to extinction. However, to date, studies on the interactive effects of rising [CO2] and warming have focussed on just a few widely distributed plant species. Wollemi pine (Wollemia nobilis W.G.Jones, K.D.Hill, & J.M.Allen), formerly widespread in Australia, was reduced to a remnant population of fewer than 100 genetically indistinguishable individuals. Here, we examined the interactive effects of three [CO2] (290, 400 and 650 ppm) and two temperature (ambient, ambient + 4°C) treatments on clonally-propagated Wollemi pine grown for 17 months in glasshouses under well-watered and fertilised conditions. In general, the effects of rising [CO2] and temperature on growth and physiology were not interactive. Rising [CO2] increased shoot growth, light-saturated net photosynthetic rates (Asat) and net carbon gain. Higher net carbon gain was due to increased maximum apparent quantum yield and reduced non-photorespiratory respiration in the light, which also reduced the light compensation point. In contrast, increasing temperature reduced stem growth and Asat. Compensatory changes in mesophyll conductance and stomatal regulation suggest a narrow functional range of optimal water and CO2 flux co-regulation. These results suggest Asat and growth of the surviving genotype of Wollemi pine may continue to increase with rising [CO2], but increasing temperatures may offset these effects, and challenges to physiological and morphological controls over water and carbon trade-offs may push the remnant wild population of Wollemi pine towards extinction.

Autumn photosynthetic decline and growth cessation in seedlings of white spruce are decoupled under warming and photoperiod manipulations

“…High growth temperatures could also have increased mesophyll conductance, increasing chloroplastic CO 2 concentrations around Rubisco, thereby increasing our apparent V cmax . High measurement temperatures generally increase mesophyll conductance, although the strength of this response varies between species (von Caemmerer & Evans ), and the response of mesophyll conductance to growth temperature is variable and currently unclear (Lewis et al ).…”

Plant carbon metabolism and climate change: elevated CO2 and temperature impacts on photosynthesis, photorespiration and respiration

“…A similar effect has been seen in other studies (Wang et al ., ). In contrast, in studies where A net is not reduced by warming, either because the species thermally acclimates or the degree of warming imposed is small, elevated CO 2 stimulates A net in the combined CO 2 and temperature treatments (Teskey, ; Lewis et al ., , ; Ghannoum et al ., ; Edwards et al ., ; Lamba et al ., ). So while high CO 2 may stimulate A net across a wide range of temperatures, plants may still have decreased carbon uptake compared to current growth conditions.…”

Leaf photosynthetic, economics and hydraulic traits are decoupled among genotypes of a widespread species of eucalypt grown under ambient and elevatedCO2

“…Leaf 13 C composition (d 13 C leaf ) was measured using an Isochrom continuous-flow mass spectrometer (Micromass, Manchester, UK) following combustion in the elemental analyser. d 13 C leaf was converted to discrimination values using mean values for previously measured 13 C composition in the aCO 2 and eCO 2 treatments in the glasshouse: d 13 C air ; À9Á83& and À17Á02& for aCO 2 and eCO 2 , respectively, relative to Vienna Pee Dee Belemnite (Lewis et al 2015). Leaf carbon isotope discrimination (D 13 C) is inversely related to d 13 C leaf , and is calculated as: D 13 C = (d 13 C aird 13 C leaf )/ (1 + d 13 C leaf /1000) (Farquhar & Richards 1984).…”