The effect of external pH on two laboratory-cultured acid-intolerant species (Chlorella pyrenoidosa Chick and Scenedesmus qudaa Turp.Breb.) and one acid-tolerant species from a natural population (Euglena mutabilis Schmitz) was examined by measuring internal pH. These measurements were made with the weak acid 'C-dimethyloxazolidine-2,4-dione after cels had been incubated for 2 and 6 hours at external pH levels from 3.0 to 8.0. Photosynthetic and respiration rates of the three species were also measured over the range of external pH levels.AU three species regulated their internal pH levels over the 6-hour incubation time. C. pyrenoidosa and S. qa had internal pH levels around 7.0, regardless of external pH. E. mutabilis had a wider internal pH range, from 5.0 at low external pH to 8.0 at high external pH. External pH had no effect on either photosynthetic or respiration rates. Statistical comparisons showed that there was a significant difference between the acid-intolerant and acid-tolerant species with regard to the level of internal pH maintained and the response of internal pH to external pH.Many streams in Pennsylvania and other parts of Appalachia have become polluted with H2SO4 from coal mines in the region. As a consequence, the pH levels in these streams are very low, in the range of 1.4 to 4.5 (6). The low environmental pH, along with other factors such as high acidity and high iron concentrations, strongly affects the biota of these streams (3). Algal species diversity is quite low (3, 24) and decreases as the pH level decreases. Nevertheless, certain species of algae flourish in these streams (3,10,24).Studies, such as those cited, have characterized a number of aspects ofnatural populations of these algae. However, little about the physiology at low external pH of acid-tolerant species is known.The measurement of internal (cytoplasmic) pH with ['4CJDMO2 provides one method by which the effect of external pH on a cell can be investigated (see Ref. 15 for a review of internal pH and methods of its measurement). None of the algae that have been studied with this method have been acid-tolerant species. Furthermore, internal pH levels have not been measured when external pH levels are as low as those encountered by acid-tolerant species.In this study, [(4CIDMO was 3.0 to 8.0. For comparative purposes, the internal pH levels of two laboratory-cultured acid-intolerant species were also measured over the same external pH range. The objective of the study was to determine whether or not the three species maintained constant internal pH levels regardless of external pH and whether there were differences between the internal pH levels ofthe acid-tolerant species and the acid-intolerant species.Results of the internal pH measurements indicate that differences do exist in both the actual values of internal pH that the acid-tolerant and acid-intolerant species have and in the way in which the internal pH of each species responds as external pH changes. MATERIALS AND METHODSOrganisms. The two acid-in...
P h o t o s y n t h e t i c uptake of H 14c03' by phytoplankton i n a s m a l l f r e s h w a t e r pond was measured on s i x d i f f e r e n t d a t e s . N i t r a t e and phosphate c o n c e n t r a t i o n s d i d n o t l i m i t t h e p h o t o s y n t h e t i c r a t e s o f t h e s e phytoplankton. L i g h t i n t e n s i t y and C02 c o n c e n t r a t i o n s d i d a f f e c t p h o t o s y n t h e s i s , w i t h d i s s o l v e d Cog d e f i n i t e l y l i m i t i n g p h o t o s y n t h e s i s on two of t h e d a t e s and p o s s i b l y l i m i t i n g i t on a t h i r d d a t e . C02-l i m i t a t i o n of p h o t o s y n t h e s i s o c c u r r e d even i n t h e p r e s e n c e of h i g h c o n c e n t r a t i o n s of HC03-(2-3 mM) on days when t h e r e was a l a r g e s t a n d i n g crop of a c t i v e l y p h o t o s y n t h e s i z i n g phytoplankton.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.