Seasonal Effects on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris

Chloroplasts were isolated from primary needles of 1-year-old seedlings and from secondary needles of a 20-year-old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20-year-old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1-year-old showed the same general trends as observed in the 20-year-old tree, but the changes were less pronounced. However, in snow-covered seedlings the PSI-mediated electron transport and the electron transport from H₂O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyll a antennae closely associated with the two photosystems than of the light harvesting chlorophyll a/b complex. In this case, too, the changes were more pronounced in the 20-year-old tree than in the 1-year-old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter were mainly reversed during spring.     

Assessment of genetic and pheromonal diversity of the Cydia strobilella species complex (Lepidoptera: Tortricidae)

Combining pheromone trapping and genetic analyses can be useful when trying to resolve complexes of closely related insect taxa that are difficult to distinguish based on morphological characters. Nearctic and Palearctic populations of the spruce seed moth, Cydia strobilella L., have been considered taxonomically synonymous since 1983, but more recent work revealing distinct sex pheromones for Canadian and Swedish moths suggest that populations in the two regions belong to different species. In order to test this hypothesis, we performed field trapping using different pheromone lures at ten sites in North America, Europe and Asia, and reconstructed phylogenetic relationships among trapped moths using mitochondrial (cytochrome oxidase subunit I) and nuclear (elongation factor 1 alpha) DNA sequence data. Trapping data and tree topologies for both genes revealed distinct pherotypes in North America and Eurasia. A genetically distinct population from China was investigated further with respect to its sex pheromone. Electrophysiological data indicated that Chinese females produce a deviant ratio of the sex pheromone components (dienic acetates) compared to Swedish females. However, trapping experiments in both areas revealed a similar broad response profile in males to a wide range of acetate ratios, and these populations should be considered taxonomically synonymous. A previous suggestion of an agonistic effect on the attraction of C. strobilella males in Sweden when adding the corresponding alcohols to the binary acetate blend was also tested in Sweden as well as in China, with no observed effect on attraction of males. In conclusion, our study demonstrates the great potential of using pheromone trapping as a tool for identification and delimitation of taxa within cryptic species complexes. Based on our data, Nearctic and Palearctic populations of C. strobilella should be considered different species, and C. youngana Kearfott stat. rev. is resurrected here as valid name for North American populations, which was the case before the revision in 1983.     

Survival of parent and brood adult bark beetles, Ips typographus, in relation to size, lipid content and re-emergence or emergence day

ABSTRACT. This study investigated a possible trade-off between bark beetle reproductive effort and future survival. Parent adult Ips typographus (L.) (Coleoptera: Scolytidae) were collected when they re-emerged from a laboratory culture after completing their first brood and held at constant temperatures of 4 or 25^oC. As a comparison, emerging brood adults were collected and held at 25^oC. The longevity of the beetles was related to when they re-emerged or emerged (measured in days since parent introduction) and to their size (pronotal width), fresh weight and lipid content at collection, by multiple regression analysis. The expression (fresh weight x pronotal width ^-2.6), used as an estimate of lipid content of the living beetles, was significantly correlated (r=0.67, P<0.001) with the actual (extracted) lipid content. At 25^oC, fat content was the variable most strongly correlated with survival time in all beetle groups except parent females. In both parent and brood females, re-emergence or emergence day, respectively, contributed significantly to the explanation of survival time, whereas pronotal width and fresh weight never contributed significantly to the regression equation. At 4^oC, fat content was not estimated but, re-emergence day was negatively correlated with survival time. In conclusion, beetles with high fat content and re-emerging or emerging early have longer expected survival than beetles leaving the log later or containing less fat. This means that females laying a large first brood might suffer a somewhat higher mortality than females laying a smaller brood.     

The evolutionary ecology of cheating: does superficial oviposition facilitate the evolution of a cheater yucca moth?

Abstract 1. A major question in the study of mutualism is to understand how mutualists may revert to antagonists that exploit the mutualism (i.e. switch to cheating). In the classic pollination mutualism between yuccas and yucca moths, the cheater moth Tegeticula intermedia is sister to the pollinator moth T. cassandra. These moth species have similar ovipositor morphology, but T. intermedia emerges later, oviposits into fruit rather than flowers, and does not pollinate. 2. We tested if the pollinator, T. cassandra, was pre‐adapted to evolve a cheater lineage by comparing its emergence and oviposition behaviour on yucca fruit to a distantly related pollinator, T. yuccasella, that differs in ovipositor morphology and oviposition behaviour. We predicted that if T. cassandra was pre‐adapted to cheat, then these pollinators would emerge later and be able to oviposit into fruit in contrast to T. yuccasella. 3. Contrary to expectations, a common garden‐rearing experiment demonstrated that emergence of T. cassandra was not significantly delayed relative to T. yuccasella. Moth emergence patterns overlapped broadly. 4. No choice oviposition experiments with female moths demonstrated that both pollinator species attempted to oviposit into fruit, but only T. cassandra was successful. Four out of 84 T. cassandra successfully oviposited into older fruit, whereas zero out of 79 T. yuccasella oviposited into older fruit. The rarity of the cheating behaviour in pollinators, however, meant that no significant difference in oviposition ability was detected. 5. The results suggest that a shift in emergence phenology is likely not a pre‐adaptation to the evolution of cheating, but that the ability to successfully lay eggs into fruit may be. The results also demonstrate that cheating attempts are rare in these pollinator species and, hence, the evolutionary transition rate from pollinator to cheater is likely to be low.     

Materials and methods for carbon dioxide and water exchange analysis§

Abstract Some of the materials which are commonly used in equipment for carbon dioxide and water exchange analysis can adsorb substantial amounts of carbon dioxide and water and, thus, may cause large experimental errors. Also presented are procedures for determining the influence of light intensity, carbon dioxide concentration, and temperature upon photosynthesis and transpiration.     

The phylogeny of a mutualism: evolution and coadaptation between Trollius and its seed-parasitic pollinators

Interactions between seed-parasitic pollinators and their hosts provide useful model systems for the analysis of evolution of mutualism and potential coevolution between plants and insects. Here I present the systematics, pollination ecology and evolution of one of these interactions. I have documented and analysed the phylogenetic and geographic associations between Trollius (Ranunculaceae: 18 spp.) and Chiastocheta (Diptera: Anthomyiidae; 17 spp.), a host-specific genus of seed-parasitic flies that pollinate their host plants to varying extent. Their interactions are usually facultative mutualisms, but in the specialized T. europaeus three fly species are obligate mutualists and a fourth species is an antagonist. The distribution patterns of fly species among Trollius species suggest that the flies evolved in associations with five highly derived Trollius species, and secondarily colonized four more primitive taxa in the parts of their ranges that overlapped with primary hosts. In general, host specificity is maintained primarily through allopatry, with colonization occurring in regions of overlap between parapatric taxa. Fly speciation has occurred in allopatry, both within and among host taxa. Cospeciation is not evident, but convergent evolution in Trollius flowers of several traits, viz. orange sepals, elongated staminodia and increased carpel number per flower, may be the result of mutualism with Chiastocheta.     

Interaction between light and chilling temperature on the inhibition of photosynthesis in chilling-sensitive plants*

Abstract. Fully expanded leaves of 25°C grown Phaseolus vulgaris and six other species were exposed for 3 h to chilling temperatures at photon flux densities equivalent to full sunlight. In four of the species this treatment resulted in substantial inhibition of the subsequent quantum yield of CO₂ uptake, indicating reduction of the photochemical efficiency of photosynthesis. The extent of inhibition was dependent on the photon flux density during chilling and no inhibition occurred when chilling occurred at a low photon flux density. No inhibition occurred at temperatures above 11.5°C, even in the presence of the equivalent of full sunlight. This interaction between chilling and light to cause inhibition of photosynthesis was promoted by the presence of oxygen at normal air partial pressures and was unaffected by the CO₂ partial pressure present when chilling occurred in air. When chilling occurred at low O₂ partial pressures, CO₂ was effective in reducing the degree of inhibition. Apparently, when leaves of chilling-sensitive plants are exposed to chilling temperatures in air of normal composition then light is instrumental in inducing rapid damage to the photochemical efficiency of photosynthesis.     

Mixed Leucocyte Reaction in Multiple Sclerosis

Astorga and Williams¹ have demonstrated that leucocytes from some patients with rheumatoid arthritis (RA) have an impaired one-way mixed leucocyte reaction² (MLR) when stimulated with leucocytes from other such patients. No definite explanation of this phenomenon is given. We have investigated other diseases in which auto-immune aetiology is suspected to see whether similar phenomena are associated with them. Here we report our investigations of multiple sclerosis (MS).     

Seasonal Effects on Chlorophyll-Protein Complexes Isolated from P-inus silvestris

The seasonal changes in the relative distribution of P700 chlorophyll-protein complex a₁ and light harvesting chlorophyll-protein complex a/b were studied in a natural stand of Pinus silvestris. Similar measurements were made after artificial photobleaching of chlorophyll in pine seedlings or in isolated pine chloroplasts. The chlorophyll-protein complexes were solubilized by sodium dodecyl sulphate and separated by polyacrylamide gel electrophoresis. When autumn and winter destruction of chlorophyll occurs, the chlorophyll a antenna associated with P700 in photosystem 1 (P700-CPa₁) is relatively more affected than the light harvesting complex, which lacks a reaction centre. These results are further supported by low-temperature fluorescence emission properties of isolated chloroplasts presented in this work and elsewhere. The destruction of chlorophyll in stressing autumn and winter climates is most probably caused by photosensitized oxidation of chlorophyll.