Long Term Effects of High CO2 Concentration on Photosynthesis of Water Hyacinth (Eichhornia crassipes (Mart.) Solms)

The photosynthetic response to CO₂ concentration, light intensityand temperature was investigated in water hyacinth plants (Eichhorniacrassipes (Mart.) Solms) grown in summer at ambient CO₂ or at10000 µmol(CO₂) mol^–1 and in winter at 6000 µmol(CO₂)mol^–1 Plants grown and measured at ambient CO₂ had highphotosynthetic rate (35 µmo1(CO₂) m^–2 s^–1),high saturating photon flux density (1500–2000) µmolm^–2 s^–1 and low sensitivity to temperature in therange 20–40 °C. Maximum photosynthetic rate (63 µmol(CO₂)m^–2 s^–1) was reached at an internal CO₂ concentrationof 800 µmol mol^–1. Plants grown at high CO₂ in summerhad photosynthetic capacities at ambient CO₂ which were 15%less than for plants grown at ambient CO₂, but maximum photosyntheticrates were similar. Photosynthesis by plants grown at high CO₂and high light intensity had typical response curves to internalCO₂ concentration with saturation at high CO₂, but for plantsgrown under high CO₂ and low light and plants grown under lowCO₂ and high light intensity photosynthetic rates decreasedsharply at internal CO₂ concentrations above 1000 µmol^–1. Key words: Photosynthesis, CO₂, enrichment, Eichhornia crassipes     

Molecular Characterization of the D Surface Protein Gene Subfamily in Paramecium tetraurelia

ABSTRACT. When Paramecium tetraurelia expresses the D serotype, detectable by serum tests, high molecular mRNA could be isolated, which corresponds to the molecular mass of the D surface protein. Using this D specific mRNA as a probe for screenings in different genomic libraries a subfamily of five very similar genes was found, named α-51D, _γ1-51D, _γ2-51D, δ-51D and ε-51D. Each of them is about 8-kb long, they show regions of identity to each other, and there is no evidence that any are defective genes or pseudogenes. Up to now serotype D is the only known serotype showing this phenomenon. Another novel feature is that two of the D isogenes are closely linked. The sequence for the entire coding region of the α-51D gene has been determined, as well as the upstream and downstream noncoding regions. Its deduced amino acid sequence shows the same characteristic cysteine periodicity displayed by all other immobilization antigen (i-ag) genes from Paramecium. However, in contrast to most other such genes, tandem repeats are missing from the 7599-bp long coding region of the α-51D gene. When the sequences of the type 51D genes are compared to each other, the similarity is very high and extends to coding as well as to noncoding regions. Similarity within noncoding regions is usually only observed for allelic i-ag genes. We conclude that the type D genes constitute a family of isogenes that are nonallelic. They contain slightly different consensus sequences with possible functions as regulatory regions.     

Hydrogenosome-Methanogen Assemblages in the Echinoid Endocommensal Plagiopylid Ciliates,Lechriopyla mystax Lynch, 1930 and Plagiopyla minuta Powers, 19331

ABSTRACT. Lechriopyla mystax Lynch, 1930 and Plagiopyla minula Powers, 1933 contain hydrogenosome-methanogen assemblages similar to those reported for other plagiopylid ciliates. These assemblages are stacks of elongate ovoid hydrogenosomes alternating with methanogens; these stacks are surrounded by cisternae of the rough endoplasmic reticulum that are often accompanied by Golgi complexes. The individual methanogens in the larger ciliate, L. mystax, are about four times the volume of those in the smaller ciliate, P. minuta, but both ciliates appear to contain Gram-negative methanococcoid bacteria, possibly Methanoplanus sp. The endoplasmic reticulum-Golgi complex probably plays a significant role in exploitation of the methanogens by the host ciliate.