Photosynthesis under Low-Level SO<sub>2</sub>and CO<sub>2</sub>Enhancement Conditions in Three Duckweed Species

Loats, Ken V.; Noble, Reginald D.; Takemoto, B.K.

doi:10.1086/337227

Cited by 6 publications

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“…Duckweeds (Lemna gibba L. strain G3; Lemna valdiviana Philippi, strain 9; and Spirodela oligorhiza (Kurtz) Hegelm., strain SOH) were grown axenically on a modified Hoagland's medium (Loats et al, 1981). Sulphite-enriched media were prepared by adding anhydrous potassium sulphite to the Hoagland's medium to attain a concentration of 5 or 10 mM prior to autoclaving.…”

Section: Methodsmentioning

confidence: 99%

“…(Ferguson & Lee, 1979, but little is known about the responses of aquatic vascular plants, which are important sources of biomass in lakes and streams. Disruption of sulphur metabolism and photosynthesis has been reported for duckweeds (Lemnaceae) exposed to SO.^ Loats, Noble & Takemoto, 1981;Fankhauser, Brunold, & Erismann, 1976); however, it has not been determined whether these responses could have been caused by sulphurcontaining anions. Since lakes and streams can serve as sinks for gaseous SOj, the productivity of aquatic plants could be affected if such anions were accumulated to high enough levels.…”

Section: Introductionmentioning

confidence: 99%

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Differential Sensitivity of Duckweeds (Lemnaceae) to Sulphite

Takemoto

Noble

1986

New Phytologist

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SUMMARYFrond replication and some aspects of carbon assimilation were observed in three species of duckweed (Lemnaceae) grown at two levels of irradiance in the presence and absence of sulphite. The objectives were to examine the relationship between the inhibition of frond replication caused by sulphite, and changes in carbon assimilation, and the role of irradiance in modifying carbon assimilation and sensitivity to sulphite.Under low irradiance (40//mol m^-s~'photosynthetic photon flux density (PPFD)), inhibition of frond replication by sulphite was most pronounced in Lemnagibba, producing a slower frond doubling time and reduced frond fresh weight. Spirodela oligorhiza exhibited a slower doubling time only, whereas neither parameter was aflFected in Lernna vatdiviana. In all species, chlorophyll content increased in response to sulphite enrichment. Soluble protein levels increased when frond replication was significantly inhibited in L. gibba and S. oligorhiza. Photosynthesis and dark respiration rates were reduced in all species by 10 mM sulphite while ribulose bisphosphate carboxylase activity on a soluble protein basis was increased up to 13 %• Reduced carbon assimilation may have contributed to decreased frond replication in L. gibba and S. oligorhiza.In all species, photosynthesis and ribulose bisphosphate carboxylase activity were enhanced under high irradiance (200 //mol m ' •' s'' PPFD). These physiological responses to elevated Hght appear to have contributed to faster rates of frond replication in all three species, and reduced sensitivity of frond replication to sulphite in L. gibba and 5. oligorhiza. It is postulated that the stimulation of carbon assimilation under high irradiance is an important physiological response contributing to the modification by the photoenvironment of the sensitivity of duckweeds to sulphite.

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Section: Methodsmentioning

confidence: 99%