A comparative study on diurnal changes in metabolite levels in the leaves of three crassulacean acid metabolism (CAM) species, Ananas comosus, Kalancho? daigremontiana and K. pinnata.

A comparative study on diurnal changes in metabolite levels associated with crassulacean acid metabolism (CAM) in the leaves of three CAM species, Ananas comosus (pineapple), a hexose-utilizing species, and Kalancho? daigremontiana and K. pinnata, two starch-utilizing species, were made. All three CAM species showed a typical feature of CAM with nocturnal malate increase. In the two Kalancho? species, isocitrate levels were higher than citrate levels; the reverse was the case in pineapple. In the two Kalancho? species, a small nocturnal citrate increase was found and K. daigremontiana showed a small nocturnal isocitrate increase. Glucose 6-phosphate (G-6-P), fructose 6-phosphate (F-6-P) and glucose 1-phosphate (G-1-P) levels in the three CAM species rose rapidly during the first part of the dark period and decreased during the latter part of the dark period. The levels of the metabolites also decreased during the first 3 h of the light period, then, remained little changed through the rest of the light period. Absolute levels of G-6-P, F-6-P and G-1-P were higher in pineapple than in the two Kalancho? species. Fructose 1,6-bisphosphate (F-1,6-P(2)) levels in the three CAM species increased during the dark period, then dramatically decreased during the first 3 h of the light period and remained unchanged through the rest of the light period. The extent of nocturnal F-1,6-P(2) increase was far greater in the two Kalancho? species than in pineapple. Absolute levels of F-1,6-P(2) were higher in the two Kalancho? species than in pineapple, especially during dark period. Diurnal changes in oxaloacetate (OAA), pyruvate (Pyr) and phosphoenolpyruvate (PEP) levels in the three CAM species were similar.     

Crassulacean acid metabolism (CAM) in Kalanchoë: Changes in intercellular CO2 concentration during a normal CAM cycle and during cycles in continuous light or darkness

In the crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana, the internal CO₂ concentrations were measured throughout CAM cycles by gas chromatography. Under normal dark-light cycles, the internal CO₂ concentration was near that of the ambient air and increased up to 0.5% during the phase of maximum malate decarboxylation. A sharp increase in internal CO₂ concentration occurring after the first 12 h of the cycle was exhibited by the plants both when there was a normal day-night cycle and when the night was replaced by illumination, and also when the light period was replaced by darkness. Thus, the increase in internal CO₂ in the morning does not appear to be primarily determined by a light-on signal or by alterations of temperature rather than by inherent factors of the leaves. This view is supported further by a steep increase in ¹⁴CO₂ production from labeted malate occurring during extended darkness at a time when the light period would normally begin. The results are discussed in particular in relation to of how CAM can control stomata movement.Abbreviation CAM Crassulacean acid metabolism     

Crassulacean acid metabolism (CAM) in Kalanchoë daigremontiana: Temperature response of phosphoenolpyruvate (PEP)-carboxylase in relation to allosteric effectors

Net CO₂ dark fixation of Kalanchoë daigremontiana varies with night temperature. We found an optimum of fixation at about 15° C; with increasing night temperature fixation decreased. We studied the temperature dependence of the activity of phosphoenolpyruvate (PEP)-carboxylase, the key enzyme for CO₂ dark fixation. We varied the pH, the substrate concentration (PEP), and the L-malate and glucose-6-phosphate (G-6-P) concentration in the assay. Generally, lowering the pH and reducing the amount of substrate resulted in an increase in activation by G-6-P and in an increase in malate inhibition of the enzyme. Furthermore, malate inhibition and G-6-P activation increased with increasing temperature. Activity measurements between 10° C and 45°C at a given concentration of the effectors revealed that the temperature optimum and maximum activities at that optimum varied with the effector applied. Under the influence of 5 mol m^-3 L-malate the temperature optimum and maximum activity dropped drastically, especially when the substrate level was low (at 0.5 mol m^-3 PEP from 32° C to 20° C). G-6-P raised the temperature optimum and maximum activity when the substrate level was low. If both malate and G-6-P were present, intermediate values were measured. We suggest that changes in metabolite levels in K. daigremontiana leaves can alter the temperature features of PEP-carboxylase so that the observed in vivo CO₂ dark fixation can be explained on the basis of PEP-carboxylase activity.Abbreviations PEP-c phosphoenolpyruvate carboxylase - CAM crassulacean acid metabolism - PEP phosphoenolpyruvate - G-6-P glucose-6-phosphate     

Phenotypic Adaptation of Tonoplast Fluidity to Growth Temperature in the CAM Plant Kalanchoë daigremontiana Ham. et Per. is Accompanied by Changes in the Membrane Phospholipid and Protein Composition

The present study deals with the phenotypic adaptation of tonoplast fluidity in the CAM plant Kalancho? daigremontiana to changes in growth temperature. Tonoplast fluidity was characterized by measuring fluorescence depolarization in membranes labeled with fluorescent fatty acid analogues and by following formation of eximeres in membranes labeled by eximere-forming fluorophores. With both techniques it was found that exposure of the plants to higher growth temperature compared with the control decreased the fluidity of the tonoplast while exposure to lower growth temperature caused the opposite. Three hours of high temperature treatment (raised from 25°C to 35°C; ``heat shock') were sufficient to decrease the tonoplast fluidity to roughly the same extent as growth under high temperature for 30 days. The phenotypic response of tonoplast fluidity to changes in growth temperature was found only in the complete membrane, not however in the lipid matrix deprived of the membrane proteins. Heat treatments of the plants decreased the lipid/protein ratio while exposure to low temperature (for 30 days) increased it. Heat treatments led to a decrease in the percentage of linolenic acid (C18:3) and linoleic acid (C18:2), heat shock and low temperature treatments induced an increase in the percentage of linoleic acid (C18:3), with concomitant decrease in the percentage of linoleic acid (C18:2). However, in the case of heat shock, increase in linolenic acid concerned mainly monogalactosyldiacylglycerol, while with low temperature treatment linoleic acid increased in phosphatidylcholine. Both treatment of the plants with high and low temperature led to a slight decrease in the contribution of phosphatidylcholine and phosphoethanolamine to the total phospholipid content of the tonoplast. High-temperature treatment of the plants not only decreased the phospholipid/protein ratio in the tonoplast, but also led to the occurrence of a 35 kDa polypeptide in the tonoplast which cross-reacted with an antiserum against the tonoplast H⁺-ATPase holoenzyme. The important role of membrane proteins in bringing about the phenotypic rigidization of the tonoplast was mimicked by reconstitution experiments showing that incorporation of the proteins isolated from the tonoplast into phosphatidylcholine vesicles decreased the fluidity of this membrane system. As to be expected from the analyses in the natural membrane, the degree of this effect depended on the phospholipid/protein ratio. Received: 4 March 1998/Revised: 28 July 1998     

Chromosome studies on capsicum (Solanaceae) I. Karyotype analysis in C. Chacoënse

The somatic chromosomes and karyotypes of two Argentine populations of Capsicum chacoënse A. T. Hunz. have been studied, both of which have 2n=24. The karyotypes are symmetrical, being composed of 11 m paris + one st pair; two pairs of chromosomes are satellied: pairs 1 and 12 in one population and pairs 11 and 12 in the other one. A heteromorphic pair of satellited chromosomes in one individual suggests a spontaneous reciprocal translocation. Results are compared with previous reports for the species and genus. Data show an intraspecific karyotype variation.     

Selective advantage of ray florets in Scalesia affinis and S. pedunculata (Asteraceae), two endemic species from the Galápagos

The presence of neuter ray florets in species within Asteraceae is generally believed to increase pollinator attraction. In the endemic Galápagos genus Scalesia (Asteraceae) a natural variation in the presence/absence of neuter ray florets is found. To evaluate whether the presence of ray florets plays a selective role on female reproductive success we chose two species of Scalesia, Scalesia affinis that carries ray florets and S. pedunculata that is rayless. On Santa Cruz Island capitula of S. pedunculata were equipped with fake ray florets while others were untouched. On Isabela Island ray florets were removed on half of the capitula of S. affinis. In S. affinis rayed capitula received more pollinators and more pollen, which resulted in a significantly higher embryo production. In S. pedunculata no effect on embryo production was found. The disagreement between the two species may correspond to a difference in visitation frequency, S. pedunculata receiving many more visit than S. affinis. Thus, ray floret development proved beneficial in pollinator-restricted localities.     

Paedomorphosis in two small species of toothed whales (Odontoceti): how and why?

To evaluate and assess the ontogenetic background for paedomorphosis in phocoenids, samples of 144 harbour porpoises, 81 white‐beaked dolphins, and 130 Commerson's dolphins were compared in terms of the development of epiphyseal fusion, cranial suture fusion, and ontogeny of cranial shape. Harbour porpoises and Commerson's dolphins terminated growth and development of all investigated traits sooner than white‐beaked dolphins, leading to lesser degrees of fusion of skeletal elements and less postnatal allometric development. The latter occurred even though shape in the two paedomorphic species developed at twice the rate relative to the size of white‐beaked dolphins. These observations imply that progenetic evolution has occurred convergently in phocoenid and Cephalorhynchus ancestors. The truncated ontogenies allow sexual maturity to be attained earlier and provide a greater reproductive potential. Both species inhabit similar temperate productive habitats and, hence, ecological factors are proposed to have supplied the selection pressures leading to progenesis. Constant prey availability must be a prerequisite for the observed phenomena because frequent food‐intake is necessitated by the limited capacity for energy storage and high heat‐loss entailed by the resulting small body sizes. Progenesis has rarely been proposed in mammal species. This may reflect rarity or that mammalian expressions of progenesis are less obvious. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 278–295.     

Dynamics of Kudoa camarguensis (myxosporean) infection in two gobiid species,Pomatoschistus microps and P. minutus (Teleostei: Pisces), in the Rhĵne River delta,France

The occurrence of the myxosporean parasite Kudoa camarguensis was surveyed monthly during 1997 in a brackish-water lagoon of the Rh?ne River delta (France). K. camarguensis was found on its typical host, Pomatoschistus microps, and on an additional host, P. minutus. Prevalence and mean abundance were higher in the typical host than in the additional host due to differences in the temporal occupancy of the lagoon by the 2 species. The temporal occurrence of this myxosporean parasite is discussed in relation to the migratory habits of P. minutus and the sedentary habits of P. microps.     

Note on the types of two Stenus‐species described by L. Fairmaire et Ph. Germain 1861 (Coleoptera,Staphylinidae)

Remarks on the species of Chilian Stenus described by Fairmaire et Germain are given, the holotype of S. anthrax was found, and a lectotype of S. pertusus is designated.     

Precence of β-Carotene and Xantophylls in two species of the genus Niphargus (Crustacea: Amphipoda)

The presence of carotenoids in the Niphargus tatrensis Wrzesniowski and Niphargus aquilex schellenbergi Karaban has been investigated. In extracts separated by means of column and thin-layer chromatography, the following carotenoids were identified:

1. in Niphargus tatrensis: β-carotene, astaxanthin ester, rubixanthin, celaxanthin and astaxanthin.
2. in Niphargus aquilex schellenbergi: cantha-xanthin, astaxanthin ester, isozeaxanthin (only from Jeker), 4-keto-4′-hydroxy-β-carotene (only from Terzietebronbos), rubixanthin, celaxanthin and astaxanthin.

It was not possible to identifity the sexth fractions.     

Is Oryza malampuzhaensis Krish. et Chand. (Poaceae) a valid species? Evidence from morphological and molecular analyses

Phylogenetic relationship between O. malampuzhaensis Krish. et Chand. (2n = 4x = 48; Poaceae, Oryzeae), a South Indian endemic wild rice with a disputed taxonomic identity, and eight other species belonging to the O. officinalis complex of the genus Oryza was examined using 62 morphological characters and 445 random amplified polymorphic DNA (RAPD) markers. Multivariate and cluster analyses using both the data sets clearly separated all accessions of O. malampuzhaensis into a distinct group. Genetic distances between O. malampuzhaensis and other species in O. officinalis complex were comparable with the distance between any other two taxa with species rank in this complex. Case-by-case taxonomic treatment of O. malampuzhaensis in relation to other species examined is presented. A taxonomic key for the discrimination of O. malampuzhaensis from other species in the O. officinalis complex has been constructed. Based on the present results, we strongly argue to restore the species rank to O. malampuzhaensis, as originally proposed by Krishnaswamy and Chandrasekharan (1958).     

A comparative study on the regulation of C3 and C4 carboxylation processes in the constitutive crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana and the C3-CAM intermediate Clusia minor

A comparison of carbon metabolism in the constitutive crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perr. and the C₃-CAM intermediate Clusia minor L. was undertaken under controlled environmental conditions where plants experience gradual changes in light intensity, temperature and humidity at the start and end of the photoperiod. The magnitude of CAM activity was manipulated by maintaining plants in ambient air or by enclosing leaves overnight in an atmosphere of N₂ to suppress C₄ carboxylation. Measurements of diel changes in carbonisotope discrimination and organic acid content were used to quantify the activities of C₃ and C₄ carboxylases in vivo and to indicate the extent to which the activities of phosphoenolpyruvate carboxylase (PEPCase), ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and decarboxylation processes overlap at the start and end of the photoperiod. These measurements in vivo were compared with measurements in vitro of changes in the diel sensitivity of PEPCase to malate inhibition. The results demonstrate fundamental differences in the down-regulation of PEPCase during the day in the two species. While PEPCase is inactivated within the first 30 min of the photoperiod in K. daigremontiana, the enzyme is active for 4 h at the start and 3 h at the end of the photoperiod in C. minor. Enclosing leaves in N₂ overnight resulted in a two-to threefold increase in PEPCase-mediated CO₂ uptake during Phase II of CAM in both species. However, futile cycling of CO₂ between malate synthesis and decarboxylation does not occur during Phase II in either species. In terms of overall carbon balance, C₄ carboxylation accounted for ≈ 20% of net daytime assimilation in both species under control conditions, increasing to 30–34% after a night in N₂. Although N₂-treated leaves of K. daigremontiana took up 25% more CO₂ than control leaves during the day this was insufficient to compensate for the loss of CO₂ taken up by CAM the previous night. In contrast, in N₂-treated leaves of C. minor, the twofold increase in daytime PEPCase activity and the increase in net CO₂ uptake by Rubisco during Phase III compensated for the inhibition of C₄ carboxylation at night in terms of diel carbon balance.