Growth and photosynthetic response of nine tropical species with long-term exposure to elevated carbon dioxide

Abstract

Seedlings of nine tropical species varying in growth and carbon metabolism were exposed to twice the current atmospheric level of CO for a 3 month period on Barro Colorado Island, Panama. A doubling of the CO concentration resulted in increases in photosynthesis and greater water use efficiency (WUE) for all species possessing C metabolism, when compared to the ambient condition. No desensitization of photosynthesis to increased CO was observed during the 3 month period. Significant increases in total plant dry weight were also noted for 4 out of the 5 C species tested and in one CAM species, Aechmea magdalenae at high CO. In contrast, no significant increases in either photosynthesis or total plant dry weight were noted for the C grass, Paspallum conjugatum. Increases in the apparent quantum efficiency (AQE) for all C species suggest that elevated CO may increase photosynthetic rate relative to ambient CO over a wide range of light conditions. The response of CO assimilation to internal C suggested a reduction in either the RuBP and/or Pi regeneration limitation with long term exposure to elevated CO. This experiment suggests that: (1) a global rise in CO may have significant effects on photosynthesis and productivity in a wide variety of tropical species, and (2) increases in productivity and photosynthesis may be related to physiological adaptation(s) to increased CO.

Responses of communities of tropical tree species to elevated CO 2 in a forest clearing

“…Small, or no change in biomass accumulation under elevated CO 2 conditions was also observed in ®eld experiments with Populus (Ceulemans and Mousseau 1994), in natural grassland (SchaÈ ppi and KoÈ rner 1996), and temperate forest communities (Cipollini et al 1993). These studies are in contrast to results of studies with tropical plants in pots (e.g., Oberbauer et al 1985;Hogan et al 1991;Ziska et al 1991;Winter and Lovelock, in press), and also to studies of other natural (e.g., Drake 1992;Norby et al 1992;WuÈ rth et al, in press ) and managed (e.g., Idso et al 1991) ecosystems, all of which have shown enhancements in productivity under elevated CO 2 . One explanation as to why plants in some experiments do not show enhancements in productivity under elevated CO 2 is that resources other than carbon are limiting growth under elevated CO 2 (KoÈ rner 1993).…”

“…Experiments assessing the in¯uence of elevated CO 2 on the productivity of plant species from tropical ecosystems have shown con¯icting results. Plants grown individually in pots have shown increases in biomass accumulation when kept under elevated CO 2 (Oberbauer et al 1985;Ziska et al 1991;Winter and Lovelock, in press), while those in experiments where plants have been grown in competing arrays (Reekie and Bazzaz 1989), or in glasshouse-maintained micro-ecosystems (KoÈ rner and Arnone 1992; Arnone and KoÈ rner 1995) have shown very little increase in biomass accumulation.…”

“…This is because species may have dierential sensitivities to elevated CO 2 which might alter their competitive abilities (Oberbauer et al 1985;Reekie and Bazzaz 1989;Ziska et al 1991;Ceulemans and Mousseau 1994). Because of the enormity of the task of assessing individual species responses to elevated CO 2 , especially in natural ecosystems, it has been suggested that research focus on understanding the response of representative species of functional groupings of plants to elevated CO 2 .…”

Gas exchange and carbon isotope composition of Ananas comosus in response to elevated CO2 and temperature

“…Zhu (1995) and Zhu, Bartholomew & Goldstein (1997) obtained significant increases in total plant dry mass of A. comosus grown at elevated CO 2 in two separate studies. We attribute the lack of a CO 2 response in the study of Ziska et al (1991) to waterlogging due to twice-daily watering of pots to saturation. Waterlogging of A. comosus rapidly damped the diurnal change in leaf titratable acidity and reduced growth (Min 1995 (Winter & Engelbrecht 1994).…”

Canopy photosynthesis of crops and native plant communities exposed to long‐term elevated CO2

“…In a study of the tussock tundra dominated by E. vaginatum, Tissue & Oechel (1987) reported photosynthetic capacity completely acclimated to elevated CO 2 treatment within 3 weeks, after which plants grown at 660cm 3 m-3 had the same rate of photosynthesis as those grown and tested at 330cm 3 m-3 • But not all studies of plants acclimating to elevated CO 2 have shown reduced capacity for photosynthesis. Some studies have reported either an increase or no change in photosynthetic capacity of elevated CO 2 Conroy, 1989;Du Cloux et al, 1989;Hollinger, 1987;Radin et al, 1987;Valle et al, 1985;Ziska et al, 1991). See also the paper by W. Arp in this issue (pp.…”