Physodes and the phenolic compounds of brown algae. Isolation and characterization of phloroglucinol polymers from Fucus vesiculosus (L.)

A series of vanillin-reactive compounds has been isolated from extracts of the brown alga Fucus vesiculosus. The first three members of this series have been examined by mass spectrometry, nuclear magnetic resonance spectrometry, and chemical methods, and were shown to be phloroglucinol, its phenyl-linked dimer, and a timer also composed of phloroglucinol units. Evidence is presented for the presence of tetrameric, pentameric, and hexameric phloroglucinol derivatives. Polymeric vanillin-reactive compounds were isolated and separated into two fractions. Oxidative hydrolysis of the major one produced phloroglucinol and related oligomers in low yields. The classical vanillin reactivity of physodes may thus be attributed to phloroglucinol-containing derivatives, as originally proposed by Crato (Crato, E.: Ber. Dtsch. Bot, Ges. 10, 295-302 (1892)).     

Unisexual flowers as a robust synapomorphy in Cariceae (Cyperaceae)? Evidence for bisexual flowers in Schoenoxiphium

Cariceae, the largest tribe within Cyperaceae, comprises about 2000 species in five genera. Cariceae is usually considered to be distinct from other Cyperaceae by the presence of exclusively unisexual flowers and by the arrangement of the pistillate flowers in single-flowered spikelets that are enclosed by the flask-like spikelet prophyll (utricle or perigynium). The nature of several morphological features of the Cariceae inflorescence remains controversial. The staminate reproductive units, as well as earlier reported bisexual reproductive units in Schoenoxiphium have been considered to be reduced partial inflorescences, or flowers. Aims of this study are to test both interpretations, based on a floral ontogenetic investigation. Moreover, for the first time, detailed SEM micrographs are presented of the inflorescence and floral development and of bisexual flowers in Schoenoxiphium. We propose that ‘inhibition of bisexuality’ is a more robust synapomorphy in Cariceae than ‘presence of only unisexual flowers’.     

Isolation and structure elucidation of tetrameric procyanidins from unripe apples (Malus pumila cv. Fuji) by NMR spectroscopy

Procyanidins are plant secondary metabolites widely consumed and known to have various physiological functions, but their bioavailability and mechanism of action are still unclear especially for larger oligomers. One of the reasons is scarce information about the detailed structure of oligomeric procyanidins. As for apple, structures of procyanidin components larger than trimers are scarcely known. In this study, 11 tetrameric procyanidins including two known compounds were isolated from unripe apples (Malus pumila cv. Fuji) and identified by NMR spectroscopic analysis and phloroglucinol degradation. As a result, the detailed structural diversity of tetrameric procyanidins in apple was established.     

Species interactions in a mixed colony of common terns (Sterna hirundo) and black skimmers (Rynchops niger)

Black skimmers (Rynchops niger) frequently nest among common terns (Sterna hirundo) on coastal islands from North Carolina to New York. Behavioural interactions among terns, skimmers, and several potential avian predator species were quantified during the 1973 breeding season at Fisherman Island, Virginia. Common terns were dominant to skimmers, chasing and dive-attacking neighbouring pairs, while skimmers rarely chased terns. Despite agonistic interactions, nesting success of both species was no different whether nearest neighbours were conspecifics or heterospecifics. Common terns chased away potential avian predators much more frequently than did skimmers. Black skimmers, then, appear to derive a ‘protective cover’ benefit from nesting among the terns. Neither nest-site limitation nor food ‘information-sharing’ appear to account for the species associations.     

Feeding rates of a mammalian browser confirm the predictions of a ‘foodscape’ model of its habitat

Adequate nutrition is a fundamental requirement for the maintenance and growth of populations, but complex interactions between nutrients and plant toxins make it difficult to link variation in plant quality to the ecology of wild herbivores. We asked whether a ‘foodscape’ model of habitat that uses near-infrared spectroscopy to describe the palatability of individual trees in the landscape, predicted the foraging decisions of a mammalian browser, the koala (Phascolarctos cinereus). Specifically, we considered four behavioural decision points at which nutritional quality may influence an animal’s decision. These were: which tree to enter, whether to feed from that tree, when to stop eating, and how long to remain in that tree. There were trends for koalas to feed in eucalypt trees that were more palatable than unvisited neighbouring conspecific trees, and than trees that they visited but did not eat. Koalas ate longer meals in more palatable trees, and stayed longer and spent more time feeding per visit to these trees. Using more traditional chemical analyses, we identified that an interaction between the concentrations of formylated phloroglucinol compounds (a group of plant secondary metabolites) and available N (an integrated measure of tannins, digestibility and N) influenced feeding. The study shows that foodscape models that combine spatial information with integrated measures of food quality are a powerful tool to predict the feeding behaviour of herbivores in a landscape.     

Biology of the Two-Spotted Spider Mite on Strawberry Plants

The two-spotted spider mite, Tetranychus urticae Koch, is commonly found on strawberry crops (Fragaria x ananassa). Strawberry plants have defensive mechanisms, which in turn influence the behavior of herbivores. The oviposition and development of the two-spotted spider mite were evaluated on the leaf disks of the cultivars ‘Aromas,’ ‘Camarosa,’ ‘Camino Real,’ ‘Diamante,’ ‘Diamante 10,’ ‘Diamante 50,’ ‘Festival,’ and ‘Seascape.’ It was observed that on cultivars such as ‘Aromas,’ ‘Camarosa,’ and ‘Seascape,’ immature survivorship was higher, but no difference was found during the developmental period from egg to adult of T. urticae. The immature development time was also longer on ‘Camarosa.’ Females laid more eggs on ‘Seascape’ (8.4 eggs/day), and the least on ‘Camarosa’ (1.0 egg/day). Mortality was higher at the larval stage and reached more than 50% in three cultivars ‘Camarosa,’ ‘Diamante,’ and ‘Seascape.’ Thus, the cultivars ‘Camarosa,’ ‘Diamante,’ and ‘Seascape’ were the ones that mostly affected the survival, development, and reproduction of T. urticae.     

Brood division in robins

Broods of fledgling robins Erithacus rubecula are sometimes divided between their parents so that each parent feeds only some of the chicks. These associations between a parent and certain of its young (‘family units’) are shown to be stable over periods of days. Brood division is most frequent in broods that are not followed by another nesting attempt. Experimental manipulation of the food supply suggests that brood division is relaxed when food is readily available. An analysis of the interactions between parents and chicks demonstrates that both adults and fledglings play a role in brood division. The possible functions of brood division are discussed with reference to ‘other types of care’, ‘parental efficiency’, ‘cheat countermeasure’ and ‘two types of chick’ hypotheses. Male parents feed chicks with shorter winglengths than do females: since females tend to have shorter winglengths than males, this suggests that chicks are cared for by parents of the opposite sex. Possible causes and consequences of this observation are discussed.     

Vitalism and the Resistance to Experimentation on Life in the Eighteenth Century

There is a familiar opposition between a ‘Scientific Revolution’ ethos and practice of experimentation, including experimentation on life, and a ‘vitalist’ reaction to this outlook. The former is often allied with different forms of mechanism – if all of Nature obeys mechanical laws, including living bodies, ‘iatromechanism’ should encounter no obstructions in investigating the particularities of animal-machines – or with more chimiatric theories of life and matter, as in the ‘Oxford Physiologists’. The latter reaction also comes in different, perhaps irreducibly heterogeneous forms, ranging from metaphysical and ethical objections to the destruction of life, as in Margaret Cavendish, to more epistemological objections against the usage of instruments, the ‘anatomical’ outlook and experimentation, e.g. in Locke and Sydenham. But I will mainly focus on a third anti-interventionist argument, which I call ‘vitalist’ since it is often articulated in the writings of the so-called Montpellier Vitalists, including their medical articles for the Encyclopédie. The vitalist argument against experimentation on life is subtly different from the metaphysical, ethical and epistemological arguments, although at times it may borrow from any of them. It expresses a Hippocratic sensibility – understood as an artifact of early modernity, not as some atemporal trait of medical thought – in which Life resists the experimenter, or conversely, for the experimenter to grasp something about Life, it will have to be without torturing or radically intervening in it. I suggest that this view does not have to imply that Nature is something mysterious or sacred; nor does the vitalist have to attack experimentation on life in the name of some ‘vital force’ – which makes it less surprising to find a vivisectionist like Claude Bernard sounding so close to the vitalists.     

Immunodiagnosis of parasitic zoonoses: purification of Toxocara canis antigens by affinity chromatography

A method of affinity chromatography developed for the purification of species-specific antigens from Toxocara canis adult worms is described. Immunochemical analyses by polyacrylamide gel electrophoresis, immunoelectrophoresis and immunodiffusion showed that ‘pure’ antigen contained fewer but more specific proteins than ‘crude’ antigen. Purified antigens and parasite sections from four parasite species (Toxocara canis, Dirofilaria immitis, Angiostrongylus cantonensis and Ascaris lumbricoides) were used in immunofluorescence tests to measure serum antibody levels in animals with natural or experimental T. canis infections and people with zoonotic toxocariasis. ‘Pure’ antigen showed higher specificity and sensitivity than ‘crude’ antigen in serological testing.     

The genome of ‘Candidatus Phytoplasma solani’ strain SA-1 is highly dynamic and prone to adopting foreign sequences

Bacteria of the genus ‘Candidatus Phytoplasma’ are uncultivated intracellular plant pathogens transmitted by phloem-feeding insects. They have small genomes lacking genes for essential metabolites, which they acquire from either plant or insect hosts. Nonetheless, some phytoplasmas, such as ‘Ca. P. solani’, have broad plant host range and are transmitted by several polyphagous insect species. To understand better how these obligate symbionts can colonize such a wide range of hosts, the genome of ‘Ca. P. solani’ strain SA-1 was sequenced from infected periwinkle via a metagenomics approach. The de novo assembly generated a draft genome with 19 contigs totalling 821,322 bp, which corresponded to more than 80% of the estimated genome size. Further completion of the genome was challenging due to the high occurrence of repetitive sequences. The majority of repeats consisted of gene arrangements characteristic of phytoplasma potential mobile units (PMUs). These regions showed variation in gene orders intermixed with genes of unknown functions and lack of similarity to other phytoplasma genes, suggesting that they were prone to rearrangements and acquisition of new sequences via recombination. The availability of this high-quality draft genome also provided a foundation for genome-scale genotypic analysis (e.g., average nucleotide identity and average amino acid identity) and molecular phylogenetic analysis. Phylogenetic analyses provided evidence of horizontal transfer for PMU-like elements from various phytoplasmas, including distantly related ones. The ‘Ca. P. solani’ SA-1 genome also contained putative secreted protein/effector genes, including a homologue of SAP11, found in many other phytoplasma species.     

Growth, gas exchange, and water-use efficiency response of two young apple cultivars to drought stress in two scion-one rootstock grafting system

The combination of two scion-one rootstock was used for two apple cultivars, ‘Pink Lady’ and ‘Qinguan’, budded on the same, one-year-old Malus hupehensis (Pamp.) Rehd. to reduce the impact of root and pot size and in order to understand the growth, water-use efficiency (WUE), and chlorophyll fluorescence characteristics. The two-scion grafted trees were planted in plastic pots under two water regimes, i.e. 70% field capacity (FC) and 55% FC. Results indicated that different scions were affected differently by drought stress. ‘Pink Lady’ had higher net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E) compared with ‘Qinguan’ under both water treatments. However, ‘Qinguan’ had lower minimal fluorescence (F₀), higher maximum fluorescence (F_m), and higher maximum photochemical efficiency of photosystem II (F_v/F_m) than ‘Pink Lady’ at 55% FC. Moreover, ‘Qinguan’ had larger shoot dry mass (ShDM) and higher intrinsic WUE_I than ‘Pink Lady’ under both water status. Gas-exchange and growth parameters, except for P _N and scion diameter, were significantly affected by the cultivar and water treatment. At 70% FC, ShDM was significantly correlated with WUE_I. Moreover, WUE_I was negatively linearly correlated with g _s at either 70 or 55% FC. These results might indicate that ‘Pink Lady’ was more sensitive to drought than ‘Qinguan’. ‘Qinguan’ apple was able to improve WUE more than ‘Pink Lady’ under both well-watered and drought conditions. The growth parameters and photosynthetic capacity of two different scions showed that the combination of double scion-one rootstock might eliminate the influences of the rootstock and pot size.     

Susceptibility of germinating cruciferous seeds to <Emphasis Type="Italic">Bagrada hilaris</Emphasis> (Hemiptera: Pentatomidae) feeding injury

Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) is a serious pest that attacks both germinating and seedling stages of a variety of cruciferous crops grown in the Central Coast of California. B. hilaris feeding on germinating seeds can cause severe stunting and plant mortality, and little is known about the feeding preference of B. hilaris for germinating seeds of major cruciferous hosts and varieties of hosts. No-choice and choice experiments were conducted in which germinating seeds in soilless and soil settings were exposed to B. hilaris adults for 7 days. Susceptibility scores were developed using B. hilaris feeding injury sites, distorted leaves, and deformed and dead plants to determine the overall B. hilaris preference for germinating host seeds. Based on the scores, the order of preference was arugula (Eruca sativa L.)?>?turnip (B. rapa L. var. rapa)?>?mizuna (B. rapa L. nipposinica)?>?kale (B. oleracea L. acephala)?>?choi (Brassica rapa L. var. chinensis)?>?broccoli (B. oleracea var. italica Plenck)?>?cauliflower (B. oleracea L. var. botrytis)?>?lettuce (Lactuca sativa L.)?>?sweet alyssum (Lobularia maritima [L.] Desv.). The lowest feeding injury was recorded on germinating lettuce and sweet alyssum seeds. Furthermore, no-choice and choice experiments were conducted with four varieties each of arugula and mizuna, twelve varieties each of kale and choi, and nine varieties/types of leafy Asian greens. The arugula varieties ‘Wild Rocket’ and ‘Spirit’ were more damaged by B. hilaris than other varieties tested. Among mizuna varieties, ‘Beira F1’ was more attractive to B. hilaris than ‘Scarlet’ or ‘Starbor F1.’ The choi varieties ‘Tokyo Bekana,’ ‘Feng Qing Choi F1,’ ‘Joi Choi F1,’ and ‘Win-Win Choi F1’ were more attractive than ‘Rosie F1.’ The leafy Asian greens variety ‘Carlton F1’ was more attractive to B. hilaris than ‘Yukina Savon,’ ‘Tatsoi OG,’ ‘Komatsuna Summerfest F1,’ ‘Red Rain F1,’ and ‘Shungiku.’ Therefore, the results suggest that not all varieties were equally susceptible to B. hilaris feeding and possibly be utilized for further field evaluation as a trap crop or developing more resistant varieties to B. hilaris.     

A SNP in the promoter region of the<Emphasis Type="Italic">VvmybA1</Emphasis> gene is responsible for differences in grape berry color between two related bud sports of grape

The VvmybA1 gene in grape (Vitis vinifera) plays a key role in the biosynthesis of anthocyanin. The grape cultivars, ‘Benitaka’ (red color) and ‘Brazil’ (black color) were the result of a bud mutation. ‘Benetika’ was derived from ‘Italia’ (green color) and ‘Brazil’ was developed from ‘Benetika’. Single sequence repeat (SSR) molecular marker analysis was performed in order to demonstrate that the three cultivars have a common pedigree. A sequence analysis of the promoter region and coding sequence of VvmybA1 revealed a base substitution between ‘Benitaka’ and ‘Brazil’ in the promoter region and a deletion of a large DNA fragment in the promoter region of ‘Italia’. Anthocyanin content and expression of the VvmybA1 and UFGT genes in ‘Brazil’ were higher than in ‘Benitaka’ and barely detectable in ‘Italia’. A transient expression system was used to introduce VvmybA1 driven by the three different promoters present in ‘Italia’, ‘Brazil’, and ‘Benitaka’ into somatic embryos of ‘Centennial Seedless’ (Vitis vinifera L.) by Agrobacterium-mediated transformation. This resulted in the production of red cells in the embryos transformed with the constructs of VvmybA1 from ‘Brazil’ and ‘Benitaka’ and no color production in embryos transformed with the VvmybA1 construct from ‘Italia’. In addition, the embryos transformed with the ‘Brazil’ construct had more red color than the embryos transformed with the ‘Benitaka’ construct. These results suggested that a SNP mutation in the promoter region of VvmybA1 in ‘Benitaka’ (red color) was responsible for the color change displayed by ‘Brazil’ (black color).     

Characterization of self-compatibility in sweet cherry varieties by crossing experiments and molecular genetic analysis

Self-compatibility is a major breeding objective in sweet cherry. The identification and characterization of new sources of self-compatibility will be useful for breeding and research purposes. In this work, self-compatibility of four local Spanish sweet cherry varieties was investigated by crossing experiments and molecular genetic analysis of two self-incompatibility loci. Crossing experiments included self- and cross-pollinations in the laboratory followed by microscopic observation of pollen tube growth and fruit set assay in the field. After crossing experiments, two accessions, ‘Son Miró’ and ‘Talegal Ahín’, were self-compatible while the other two were self-incompatible. Inheritance of S-locus and microsatellite EMPaS02 (linked to self-compatibility, Sc) were investigated in self-pollination progeny of both self-compatible genotypes. Results indicate that self-compatibility in ‘Talegal Ahín’ is similar to self-compatibility described in sweet cherry ‘Cristobalina’ and may be caused by the same mutation. That is a pollen part mutation not linked to the S-locus but linked to microsatellite EMPaS02 in cherry LG3. In ‘Son Miró’ self-compatibility seems more complex, affecting pollen and style function, and probably involving more than one mutation not described previously in sweet cherry. Together with ‘Cristobalina’, the newly described self-compatible varieties ‘Son Miró’ and ‘Talegal Ahín’ confirm the existence of unique self-compatible plant material in local germplasm from Spain that should be conserved and characterized for its use in breeding and research.     

Proanthocyanidins of barley and sorghum; composition as a function of maturity of barley ears

Sorghum vulgare seeds contain a proanthocyanidin polymer consisting largely of 2,3-cis procyanidin units with M?_n, 2500. Hordeum vulgare ears contain low levels of proanthocyanidin oligomers containing 2–4 units, and composed largely of 2,3-trans procyanidin and prodelphinidin units with catechin as the terminal unit. The concentration of the oligomers in barley ears was virtually constant throughout the 33 day growth and ripening period.     

From d’Orbigny to the Devonian: some thoughts on the history of the stratotype concept

D’Orbigny’s stratigraphic contributions were enormous, both practical and theoretical. In his practice, d’Orbigny realised the central importance of using fossil faunas to correlate strata across different countries. His ‘succession chronologique des âges du monde’ (of 1852) recognised 5 periods and 27 stages (ignoring his ‘époque actuelle’). The great majority of the latter were from two Periods, Jurassic (stages 7 to 16) or Cretaceous (17 to 23). D’Orbigny described the palaeontological characteristics, and geographical extensions, of each. Some stages he based on countries he never visited and although he never specified ‘stratotype’ localities, he referred to some as ‘étalon’, ‘le mieux’ or ‘le plus beau’. These leads proved crucial when, in the mid 20th century, stratigraphers realised that definitions of chrono-stratal units must be attempted. The first attempts at typification simply followed zoology, where a type specimen tries to define a central position within the morphological variation of a species. In 1962, an early attempt was made to define Jurassic stages by three type horizons at different type localities (or stratotypes as they were now called) for each. A central horizon was chosen as ‘lectotype section’ and upper and lower boundaries for each were defined elsewhere. In France, it was preferred to investigate original intentions at named localities, through unit-stratotypes. These allowed some nationalistic pride, since France was the home of so many d’Orbignyan stages. 1980 saw the publication Les Étages français et leurs Stratotypes. However, British Silurian stratigraphers had realised that such zoologically based concepts would produce conflict, when any defined upper boundary stratotype conflicted with the defined lower boundary of a superjacent unit. They suggested, from 1962, to define only lower boundaries, via ‘golden spikes’, at basal-boundary stratotypes. This was the method chosen for the basal Devonian stratotype at Klonk, Czech Republic, defined in 1972, and a method adopted globally from 1986. However, this was when correlations were still largely based on fossils. The explosion of so many other stratigraphies since, based on magnetic or chemical records, events etc, has produced a first reaction against the idea that such stratotypes should be so defined, while a second, potentially more major claim, is that any ‘golden spike’ concept may no longer ‘glitter’, as competing stratotype concepts may be holding back stratigraphic progress.     

Ovaries and germline cysts and their evolution in Dermaptera (Insecta)

We studied the ovary structure and initial stages of oogenesis in 15 representatives of several dermapteran taxa, including the epizoic Arixeniina. In all examined species, the ovaries are meroistic–polytrophic. The ovaries of the basal taxa (‘Pygidicranidae’, ‘Diplatyidae’, and Labiduridae) are composed of elongated ovarioles, attached to short lateral oviducts. In these groups, ovarioles contain several (more than 30) ovarian follicles in a linear arrangement. In the Eudermaptera, the ovaries are composed of 1–6 (Spongiphoridae) or 20–40 (Forficulidae, Chelisochidae) short ovarioles (containing 2 ovarian follicles only) that open to strongly elongated lateral oviducts. In all investigated dermapterans, the ovarian follicles are composed of two germline cells only: an oocyte and a polyploid nurse cell that are covered by a simple follicular epithelium. Our studies indicate that despite a rather unique morphology of the ovarian follicles in the examined species, the processes leading to the formation of the oocyte and nurse cell units are significantly different in basal versus derived taxa.The ovaries of Arixenia esau are composed of 3 short ovarioles attached to a strongly dilated lateral oviduct, ‘the uterus’, containing developing embryos. Histological analysis suggests that the origin of the oocyte and nurse cell units in this species follows the pattern described in eudermapterans.The interpretation of our results in an evolutionary context supports the monophyly of the Dermaptera and Eudermaptera, and the inclusion of the Arixeniina and Hemimerina in the latter taxon.     

Purification of a phospholipase from Botrytis and its effects on plant tissues

A phospholipase from Botrytis cinerea, grown in pure culture, was purified more than 1000-fold. Whilst it possessed no acyl hydrolase activity toward a variety of p-nitrophenyl fatty acyl derivatives, phosphatidyl choline (lecithin) acted as a substrate; the enzyme being of either type ‘A’ or ‘B’ specificity. When the purified enzyme was applied to washed beetroot discs, betacyanin leakage was induced. Loss of substances which absorb at 260 nm also occurred when washed potato tuber discs were incubated with the enzyme. Incubation with a lysosome-enriched fraction from potato sprout tissues resulted in increased acid phosphatase activity in the incubation supernatant. The phospholipase had no macerating effect on a variety of plant tissues, nor did it cause disruption of isolated protoplasts from these tissues. Studies with mitochondria from mung beans revealed no effects of the enzyme upon the respiratory activity of these organelles. The result suggested that a major site of action of the B.cinerea phospholipase was the lysosomes.     

An integumentary gland secreting a territorial marking pheromone in Atta sp.: Detailed structure and histochemistry

An abdominal pheromone-producing gland in Atta sp. was examined using light and electron microscopy techniques. The gland is composed of a bunch of juxtaposed secretory units in which the secretory ductules open on to a cribellum close to the sting base.The structure and cycles of the secreting units are described. Each includes a secretory cell with an ‘end apparatus’, ductule cells and epidermal cells. The secretory cycle of glycoproteins accumulated in the ‘end apparatus’ is discussed and a functional interpretation of the morphological components of the application system is proposed.     

Synthesis and chemiluminescence of copolymers of 5-amino-8-vinyl-phthalazine-1, 4(2H,3H)-dione with methyl methacrylate or styrene,and of α, ω-bis[5-amino-phthalazine-1,4 (2H,3H)-dion-]8-yl alkanes [=α, ω-bis(6-luminyl) alkanes]: Investigations on an intramolecular ‘distance effect’

Oligomers of 5-amino-8-vinyl-phthalazine-1,4(2H,3H)-dione exhibit about 0.05% of the chemiluminescence quantum yield of the corresponding ‘monomer unit’, i.e. 5-amino-8-ethyl-phthalazine-1,4(2H,3H)-dione which has a similar quantum yield to luminol. The quantum yields of copolymers of 5-amino-8-vinyl-phthalazine-1,4(2H,3H)-dione (1a) with methyl methacrylate or with styrene increase up to 1000-fold, relative to the quantum yield of oligomers of (1a). Thus the monomer units of methyl methacrylate or styrene appear to act as ‘spacers’ between the lumigenic groups. α,ω-Bis[(5-amino-phthalazine-1,4(2H,3H)-dion-)8-yl] alkanes show an analogue ‘distance’ effect: the chemiluminescence quantum yield increases with increasing alkane chain length. As the fluorescence of the corresponding amino phthalates (which are intermediates in the synthesis of the phthalazine diones) is only slightly influenced by the distance between the lumigenic groups it is suggested that a mainly chemical ‘distance effect’ is working here: the smaller the intramolecular distance between the hydrazide groups the more inhibition exists in respect of the oxidative reaction producing the luminol-type chemiluminescence.