Effect of the Photosynthetic Light Period on the Carbon Budget of Young Tomato Leaves

This study was carried out to elucidate the carbon budget inyoung tomato plants in photosynthetic light periods of 8, 12and 16 h after being acclimated to an 8-h light period. Thephotosynthetic rate was nearly constant for 16 h: thereforethe amount of ¹⁴C fixed was proportional to the light period(13·77 mg C per 8 h, 20·2 mg C per 12 h, 30·5mg C per 16 h). The amounts exported, lost by respiration and accumulated whenexpressed as percentages of the carbon fixed in the day differedlittle between the light periods. The leaf continued to exportcarbon at a nearly constant rate during the light periods and,for example, exported approximately twice as much during a 16-hperiod as in an 8-h light period, even though it was not acclimatedto the long light period. The amount of starch breakdown affected the amount of carbonexported and carbon lost by respiration at night, although itwas not sufficient to account for these losses altogether. Thepossible roles of carbon accumulation and respiration are alsodiscussed. Carbon budget, steady state feeding, ¹⁴C, photosynthesis, respiration, translocation, carbon metabolism, tomato, Lycopersicon esculentum Mill     

Carbon Budget in Tomato Plants as Affected by Night Temperature Evaluated by Steady State Feeding with 14CO2

A semi-closed system to label with ¹⁴C and trace photoassimilatesunder steady state conditions is described. It was used to elucidatethe effects of night temperature on the carbon budget of tomato The third leaf kept at 25 °C in 8 h light of 36 W m^–1(PAR) assimilated 13·77 mg C . d^–1. By the endof the photoperiod, 46% of the carbon assimilate was exportedto the sinks, out of which 27% was respired and 19% was accumulatedin the sinks, respectively The plants were then kept in the dark for 16 h at 15, 20, 25and 30%C. The export in the night-time increased with nighttemperature, reaching 18–27% of the carbon assimilated.Thus, the total export in a whole day amounted to 63–72%of the carbon assimilated, out of which 35 and 42% were lostby respiration and 29 and 31% was accumulated in the sinks at15 and 30 °C, respectively. Thus, accumulation in the sinksdiffered little with night temperature, while that in the sourceleaf, and hence the total accumulation, decreased with increasingnight temperature The export started early in the morning and was much greaterin the light than in the dark. In addition, the day/night ratioof export was lower at higher night temperatures The percentage distribution of ¹⁴C-assimilates to the lowerparts decreased, while that to the upper parts increased withincreasing night temperature. The calculated respiratory lossin individual sinks seemed to correspond to the distributionpattern of ¹⁴C-assimilates Carbon budget, 14C, ¹⁴C steady state feeding, translocation, respiration, assimilate distribution, temperature, tomato     

The robustness of geometric morphometrics in testing the morphological equivalence hypothesis among cichlid species from East African Great Lakes

As part of an ongoing broader investigation into whether similar morphologies among cichlid species from East African Great Lakes are due to common ancestry or convergent evolution, we used geometric morphometrics to quantitatively test the hyphothesis that Lake Tanganyika's Tropheus spp. is morphologically similar to Lake Malawi's Pseudotropheus spp. and Labeotropheus fuelleborni . Landmark-based techniques were used to investigate body shape variation and the results revealed highly significant differences among these genera with the exception of L. fuelleborni vs. Pseudotropheus ( Tropheops ) spp. An ordination of all specimens along the first two canonical variate (CV) axes indicated clear interlake separation, especially along the CV I axis, whereby Tropheus moori showed a dorsoventral expansion of the mid body section with a steeper forehead relative to Lake Malawi species. Pseudotropheus ( Maylandia ) zebra was discriminated from the rest primarily on the basis of its terminally positioned gape, which differed from the inferior subterminal gape that was prevalent in the other species. Thus, the present study reveals a pattern of parallel evolution between L. fuelleborni and Pseudotropheus ( Tropheops ) spp., but does not support an interlake convergent evolution hypothesis. Contrary to previous researchers' assertions, these results emphasize the robustness of geometric morphometrics when testing morphological equivalence hypothesis among cichlid species.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 1–9.     

Spatial heterogeneity of trophic pathways in the invertebrate community of a temperate bog

Summary 1. To examine spatial heterogeneity of trophic pathways on a small scale (<5 m diameter), we conducted dual stable isotope (δ¹³C and δ¹⁵N) analyses of invertebrate communities and their potential food sources in three patchy habitats [sphagnum lawn (SL), vascular‐plant carpet (VC) and sphagnum carpet] within a temperate bog (Mizorogaike Pond, Kyoto, Japan). 2. In total, 19 invertebrate taxa were collected from the three habitats, most of which were stenotopic, i.e. collected from a single habitat. Amongst the habitats, significant variation was observed in the isotopic signatures of dominant plant tissues and their detrital matter [benthic particulate organic matter (BPOM)], both of which were potential organic food sources for invertebrates. Site‐specific isotopic variation amongst detritivores was found in δ¹³C but not in δ¹⁵N, reflecting site‐specificity in the isotopic signatures of basal foods. The eurytopic hydrophilid beetle Helochares striatus was found in all habitats, but showed clear site variation in its isotopic signatures, suggesting that it strongly relies on foods within its own habitat. 3. The most promising potential foods for detritivores were the dead leaf stalks of a dominant plant in the VC and BPOM in the SL and carpet. An isotopic mixing model (IsoSource version 1.3.1) estimated that aquatic predators rely on unknown trophic sources with higher δ¹³C than detritus, whereas terrestrial predators forage on allochthonous as well as autochthonous prey, suggesting that the latter predators might play key roles in coupling between habitats. 4. Our stable isotope approach revealed that immobile detritivores are confined to their small patchy habitats but that heterogeneous trophic pathways can be coupled by mobile predators, stressing the importance of habitat heterogeneity and predator coupling in characterising food webs in bog ecosystems.     

Size-Structures and Reproductive Characteristics in Diploid and Triploid Populations of Disporum sessile D. Don (Liliaceae)

Abstract Disporum sessile (Liliaceae), a perennial herb of temperate forests is composed of diploid (2n=16) and triploid (2n=24) populations. The size structure differed remarkably as triploid populations had few small plants and no seedlings. Triploid flowering plants were considerably larger than diploids. Triploids that flowered were 2.5 times larger than diploids that flowered and the size of vegetative ramets produced by triploids was twice as large. In triploids, fruiting rates were quite low only with inviable seeds and vegetative propagule size was greater than that of diploids. As regards growth parameters that help to increase plant size, triploids were superior to diploids. Differences in growth and reproductive parameters between diploids and triploids may contribute to forming different patch sizes.     

Micronucleus‐Specific Bacterium Holospora elegans Irreversibly Enhances Stress Gene Expression of the Host Paramecium caudatum

ABSTRACT. The bacterium Holospora is an endonuclear symbiont of the ciliate Paramecium. Previously, we reported that paramecia bearing the macronuclear‐specific symbiont Holospora obtusa survived better than symbiont‐free paramecia, even under high temperatures unsuitable for growth. The paramecia with symbionts expressed high levels of hsp70 mRNAs even at 25 °C, a usual growth temperature. We report herein that paramecia bearing the micronuclear‐specific symbiont Holospora elegans also acquire the heat‐shock resistance. Even after the removal of the bacteria from the hosts by treatment with penicillin, the resulting aposymbiotic paramecia nevertheless maintained their heat shock‐resistant nature for over 1 yr. Like symbiotic paramecia, these aposymbiotic paramecia also expressed high levels of both hsp60 and hsp70 mRNAs even at 25 °C. Moreover, analysis by fluorescent in situ hybridization with a probe specific for Holospora 16S rRNA revealed that the 16S rRNA of H. elegans was expressed around the nucleoli of the macronucleus in the aposymbiotic cells. This result suggests the possible transfer of Holospora genomic DNA from the micronucleus into the macronucleus in symbiotic paramecia. Perhaps this exogenous DNA could trigger the aposymbiotic paramecia to induce a stress response, inducing higher expression of Hsp60 and Hsp70, and thus conferring heat‐shock resistance.     

Increase in Shedding of Intercellular Adhesion Molecule-1 in Human Malignant Melanoma Cell Lines Treated With Hyperthermia In Vitro

Human malignant melanoma cell lines were found to increase shedding of soluble intercellular adhesion molecule-1 (sICAM-1) into the culture medium when the cells were treated with hyperthermia at 41–43°C for 3–6 hr in vitro. The content of ICAM-1 in the cell lysate was also found to be increased after hyperthermia. The increased rate of ICAM-1 concentration in the cells was at maximum when they were incubated at 41°C for 3 hr. Also, the melanoma cell lines heat-treated at 41°C showed more intense immuno-fluorescence in the ICAM-1 expression on the cell surface. It remains to be investigated further whether the effects of hyperthermia on the ICAM-1 expression in melanoma cells is to augment membrane ICAM-1 expression, which in turn leads to shedding of soluble ICAM-1 or only to acceleration of shedding of sICAM-1 by unknown mechanisms.