Chemical constituents and medicinal properties of Allium species

Allium species, belonging to Alliaceae family, are among the oldest cultivated vegetables used as food. Garlic, onions, leeks and chives, which belong to this family, have been reported to have medicinal properties. The Allium species constituents have been shown to have antibacterial and antioxidant activities, and, in addition, other biological properties. These activities are related to their rich organosulfur compounds. These organosulfur compounds are believed to prevent the development of cancer, cardiovascular, neurological, diabetes, liver diseases as well as allergy and arthritis. There have also been reports on toxicities of these compounds. The major active compounds of Allium species includes, diallyl disulfide, diallyl trisulfide, diallyl sulfide, dipropyl disulfide, dipropyl trisulfide, 1-propenylpropyl disulfide, allyl methyl disulfide and dimethyl disulfide. The aim of this review is to focus on a variety of experimental and clinical reports on the effectiveness, toxicities and possible mechanisms of actions of the active compounds of garlic, onions, leek and chives.

     

New seed morphological features in Moehringia L. (Caryophyllaceae) and their taxonomic and ecological significance

Abstract

Relative growth rate (RGR) is a fundamental trait for comparative plant ecology but cannot be measured in situ, leading to problems in interpreting vegetation function. However, the components of RGR (net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), and specific leaf area (SLA)) can be calculated for wild plants from morphological measurements (leaf area, leaf dry mass, whole plant dry mass), which potentially reflect RGR. Seeds of 19 species from Italian prealpine calcareous grasslands were collected and seedlings were cultivated under controlled conditions. RGR, NAR, LAR, LWR and SLA were analysed. The results demonstrated that RGR was positively correlated with SLA and LAR (p < 0.01). Furthermore, LAR was positively correlated with LWR and negatively with NAR (p < 0.05). Monocotyledons showed significantly higher LAR, LWR and NAR than dicotyledons, as the latter allocated a greater proportion of biomass to stems, but RGR and SLA showed no such phylogenetic constraint. Therefore SLA is the most reliable indicator of RGR in ecological and functional surveys of prealpine calcareous grasslands, and has the additional advantage that it can be measured from leaf material alone. Lower mean RGR and SLA for calcareous grassland species suggests that this vegetation is less likely to recover from the effects of disturbance than meadows and dry meadows.     

Variation in growth stimulation by elevated carbon dioxide in seedlings of some C3 crop and weed species

Seven C₃ crop and three C₃ weed species were grown from seed at 360 and at 700 cm³ m^–3 carbon dioxide concentrations in a controlled environment chamber to compare dry mass, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic acclimation at ambient and elevated carbon dioxide. The dry mass at the final harvest at elevated carbon dioxide relative to that at ambient carbon dioxide was highly correlated with the RGR at the lower carbon dioxide concentration. This relationship could be quite common, because it does not require that species differ in the response of RGR or photosynthesis to elevated carbon dioxide, and holds even when species differ moderately in these responses. RGR was also measured for a limited period at the end of the experiment to determine relationships with leaf gas exchange measured at this time. Relative increases in RGR at elevated carbon dioxide at this time were more highly correlated with the relative increase in NAR at elevated carbon dioxide than with the response of LAR. The amount of acclimation of photosynthesis was a good predictor of the relative increase in NAR at elevated carbon dioxide, and the long-term increase in photosynthesis in the growth environment. No differences between crops and weeds or between cool and warm climate species were found in the responses of growth or photosynthetic acclimation to elevated carbon dioxide.     

The effect of nitrogen nutrition on growth and biomass partitioning of annual plants originating from habitats of different nitrogen availability

Summary The hypothesis was tested that faster growth of nitrophilic plants at high nitrogen (N) nutrition is counterbalanced by faster growth of non-nitrophilic plants at low N-nutrition. Ten annual plant species were used which originated from habitats of different N-availability. The species' preference for N was quantified by the N-number of Ellenberg (1979), a relative measure of nitrophily. The plants were cultivated in a growth cabinet at five levels of ammonium-nitrate supply. At low N-supply, the relative growth rate (RGR) was independent of nitrophily. At high N-supply, RGR tended to be higher in nitrophilic than in non-nitrophilic species. However, the response of RGR to N-supply was strongly and positively correlated with the nitrophily of species. Increasing N-supply enhanced partitioning to leaf weight per total biomass (LWR) and increased plant leaf area per total biomass (LAR). Specific leaf weight (SLW) and LWR were both higher in non-nitrophilic than in nitrophilic species at all levels of N-nutrition. NAR (growth per leaf area or net assimilation rate) increased with nitrophily only under conditions of high N-supply. RGR correlated positively with LAR, irrespective of N-nutrition. Under conditions of high N-supply RGR correlated with SLW negatively and with NAR positively.     

Continuous light may induce photosynthetic downregulation in onion – consequences for growth and biomass partitioning

Onions were grown in environmentally controlled growth chambers for 85 days to investigate the effect of relatively low light intensity (350 µmol m⁻² s⁻¹) at two different total irradiance periods (12-h and 24-h photoperiods) on growth and photosynthetic performance. To test whether photosynthetic downregulation occurred due to carbohydrate feedback, we used onions that differed in bulb-forming capacity. Allium fistulosum (L. cv. 'Kinka') is a non-bulbing onion, with potentially limited carbohydrate storage capacity, while Allium cepa (L. cv. 'Cal 296') is a bulb-forming onion with possibly greater carbohydrate storage capacity. In A . fistulosum , photosynthetic downregulation was observed in 24-h plants as indicated by reductions in the light- and CO₂-saturated photosynthetic capacity ( A _sat and A _max, respectively) by 26%, reduced maximum rate of carboxylation ( V _cmax) by ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) by 33%, reduced maximum rate of electron transport ( J _max) by 27% and 3-fold higher foliar sugar concentration. In contrast, the photosynthetic and biochemical capacity of A . cepa was not affected by exposure to 24-h photoperiod, presumably because substantial amounts of foliar carbohydrates were re-allocated to bulbs. In 24-h A . cepa , up to 84% of total plant mass was allocated to bulbs, while in 12-h plants, more mass was allocated to leaves. Production of greater leaf area in 12-h plants compared with 24-h plants compensated for lower total daily irradiance such that 12-h and 24-h plants of both species exhibited similar daily total leaf net CO₂ exchange and plant mass at the end of the experiment.     

Control of stem nematode, Ditylenchus dipsaci, in onions, by granular nematicides applied to the soil

Aldicarb at 1.4–5.6 kg a.i. ha^-l or oxamyl at 1.3–5.2 kg a.i. ha^-1 applied over the seed furrows during sowing prevented much of the damage resulting from stem nematode attack in spring-sown onions. Rotting of bulbs in store due to stem nematode infestation was sometimes lessened by these treatments. Neither sowing onion seeds on soil ridges, nor applying aldicarb in two equal doses, one over the seed furrows during sowing, the other over the plants mid-season, controlled the nematode better or increased onion yields more than a single equivalent dose over the seed furrows. Applied as two doses in this way, aldicarb was sometimes more effective against the nematode in summer-sown onions than was an equivalent amount applied over the seed furrows during sowing. Only 2.5 kg or less aldicarb ha^-1 can be applied to onions without leaving unacceptable residues (>0.15 μg g^-1) in the harvested bulbs.     

The Interrelated Effects of Stage of Development and Seasonal Changes in Light and Temperature on the Components of Growth in Zea mays

Seeds of Orla 266, a double cross hybrid of Zea mays, were sownin pots in the open 3, 6, and 9 weeks before the individualplants were sampled at consecutive weekly intervals from theend of August. On each occasion the weights of the whole plantand its parts plus leaf area were recorded, and the proceduresof growth analysis applied to the data. Between the youngest and oldest plants over all occasions thegreatest reductions with age were for the rate of leaf expansionand the ratio of leaf area to leaf weight. The net assimilationrate (NAR) and the leaf weight ratio (LWR) were depressed leastwhile the relative growth-rate (RGR) and leaf area ratio (LAR)occupied an intermediate position. The age effects were mostpronounced for RGR, NAR and the ratio of leaf area to leaf weightat the beginning of the experiment, whereas for LAR and LWRthe divergencies were largest at the end. On the basis of the recorded changes in solar radiation andtemperature and prior studies of the interacting effects oflight and temperature on the vegetative growth of Zea it waspossible to predict for the several growth components the patternsof change which should be expected. For the youngest and intermediatepopulations there was close agreement between the expected andobserved values for RGR, NAR, and LAR and it was concluded thatthe time courses were primarily dependent on environmental factors.On the other hand, for the oldest plants from the third intervalonwards the observed values for NAR and less so for RGR werematerially above expectation. It was noted that this divergencecoincided with the rapid extension of the shoot which was confinedto the oldest plants. It is advanced that the higher NAR isassociated with the vertical separation of the leaves.     

Relative contributions of leaf area ratio and net assimilation rate to change in growth rate depend on growth temperature: comparative analysis of subantarctic and alpine grasses

The present study shows that the relative contributions of leaf area ratio (LAR) and net assimilation rate (NAR) to variation among species in relative growth rate (RGR) depend on growth temperature. We grew three subantarctic and three alpine Poa species at daytime temperatures of 7, 12 and 17 degrees C, and analysed interspecific and temperature-related variation in RGRs by growth analysis. Variation in NAR accounted for most of the interspecific differences in RGR at low growth temperature, whereas variation in both NAR and LAR contributed strongly to interspecific differences in RGR at high growth temperature. For most species, the increase in RGR from 7 to 12 degrees C was attributable to an increase in LAR, whereas the increase in RGR from 12 to 17 degrees C was attributable to an increase in NAR. There were no differences between native subantarctic and alpine species in the plasticity of growth responses to temperature. However, Poa annua, a species introduced to the subantarctic, showed much greater growth plasticity than other species. There was little difference among species in tolerance of high-temperature extremes.     

Epidemiology of Cladosporium allii and Cladosporium allii-cepae, leaf blotch pathogens of leek and onion.

Conidia of Cladosporium allii and C. allii-cepae germinated over the temperature range 2–30°C on agar with optimal responses at 15–20°C (C. allii) and 20°C (C. allii-cepae). Conidia of both fungi germinated in water and at c. 100% relative humidity (r.h.) but not at lower humidities on leaf and glass slide surfaces. Germination was more rapid when spores were applied dry to agar or leaves than when applied in water or nutrient solution. More lesions developed when conidia of C. allii-cepae were deposited dry on onion leaf discs or leaf surfaces than when they were applied suspended in water. Conidia of both fungi required 18–20 h at c. 100% r.h. to germinate and infect when applied dry to leaves. Damaging the leaves or the addition of nutrients to the leaf surface increased the incidence of infection by C. allii-cepae compared to controls. Inoculated onion bait plants placed out-of-doors developed infection after at least 17 h at c. 100% r.h. or with leaf wetness. Similar conditions were necessary for infection of bait plants exposed in onion and leek crops infected by C. allii-cepae and C. allii respectively. Disease development and spread of infection occurred at different rates over the same period in two different cultivars of leeks, with spore concentrations increasing in proportion to disease. Spore numbers in the air fell considerably when infected leeks were ploughed under.     

Effect of CO2-enrichnient on seedling physiology and growth of two tropical tree species

Seedlings of two tree species from the Atlantic lowlands of Costa Rica, Ochroma la-gopus Swartz, a fast-growing pioneer species, and Pentaclethra macroloba (Willd.) Kuntze, a slower-growing climax species, were grown under enriched atmospheric CO₂ in controlled environment chambers. Carbon dioxide concentrations were maintained at 350 and 675 μl 1⁻¹ under photosynthetic photon flux densities of 500 μol m⁻² s⁻¹ and temperatures of 26°C day and 20°C night. Total biomass of both species increased significantly in the elevated CO₂ treatment; the increase in biomass was greatest for the pioneer species, O. lagopus . Both species had greater leaf areas and specific leaf weights with increased atmospheric CO₂. However, the ratio of non-pho-tosynthetic tissue to leaf area also increased in both species leading to decreased leaf area ratios. Plants of both species grown at 675 μl 1⁻¹ CO₂ had lower chlorophyll contents and photosynthesis on a leaf area basis than those grown at 350 μl 1⁻¹. Reductions in net photosynthesis occurred despite increased internal CO₂ concentrations in the CO₂-enriched treatment. Stomatal conductances of both species decreased with CO₂-enrichment resulting in significant increases in water use efficiency.     

A novel method for evaluating the egg killing defenses and varietal resistance of the bunching onion against Liriomyza chinensis (Diptera: Agromyzidae) via the artificial inoculation of eggs

The stone leek leafminer, Liriomyza chinensis (Kato) (Diptera: Agromyzidae) , is recognized as one of the most destructive pests of the bunching onion. Varietal resistance against L. chinensis has been reported in Allium fistulosum in Japan. We report a new method for evaluating the antibiosis of bunching onions with varietal resistance to L. chinensis by artificially inoculating leaves with L. chinensis eggs. New no-choice tests were performed via the collection and artificial inoculation of L. chinensis eggs into unifacial leaves with a plunger microsyringe and the quantification of the number of individuals that reached the pupal stage in the soil after 14 days of inoculation at 24 °C; these tests were established and conducted to determine the resistance categories of several varieties of A. fistulosum. Antibiosis studies revealed a significant difference in survival to the pupal stage, forewing lengths of adults and development time from the egg to pupal stages among the resistant and susceptible varieties of A. fistulosum, indicating that antibiosis is an important factor in the varietal resistance of A. fistulosum. Furthermore, the antibiosis of the highly resistant varieties ‘Beicong’ and ‘Kokusen natsuyo’ revealed egg killing defenses against L. chinensis.     

Differences in developmental plasticity and growth rate among drought-resistant and susceptible cultivars of durum wheat (Triticum turgidum L. var. durum)

Understanding how growth and development of durum wheat cultivars respond to drought could provide a basis to develop crop improvement programmes in drought-affected tropical and subtropical countries. A greenhouse experiment was conducted to study the responses of five durum wheat cultivars to moisture stress at different developmental phases. Phenology, total dry matter (TDM), relative growth rate (RGR), leaf area ratio (LAR), net assimilation rate (NAR), leaf weight ratio (LWR), specific leaf area (SLA) and shoot:root ratio were compared. Pre-anthesis moisture stress delayed phenological development, whereas post-anthesis moisture stress accelerated it. TDM accumulation rate was different between drought-resistant and susceptible cultivars. RGR and its components changed with age and moisture availability. Drought-resistant cultivars had a high RGR in favourable periods of the growing season and a low RGR during moisture stress. In contrast, the drought-susceptible cultivar (Po) showed an opposite trend. LAR explained the differences in RGR (r=0.788) best, whereas the relationship between NAR and RGR was not significant. Even though both LWR and SLA were important factors determining the potential growth rate, LWR was of major importance to describe cultivar differences in LAR, and consequently in RGR. The drought-resistant cultivars Omrabi-5 and Boohai showed vigorous root development and/or a low shoot:root ratio. It is concluded that biomass allocation is the major factor explaining variation in RGR among the investigated durum wheat cultivars.     

Effects of irradiance on relative growth rates, net assimilation rates, and leaf area partitioning in cotton and three associated weeds

Cotton (Gossypium hirsutum L. var. `Stoneville 213'), velvetleaf (Abutilon theophrasti Medic.), redroot pigweed (Amaranthus retroflexus L.), and hemp sesbania (Sesbania exaltata [Raf.] Cory) were grown in a controlled environment room at 31/25 C day/night temperature and three irradiances: 90, 320, and 750 μeinsteins meter⁻² second⁻¹. From total dry weights and leaf areas determined at intervals during the first exponential phase of growth, we used mathematical growth analysis techniques to calculate net assimilation rates (NAR), relative growth rates (R_w), relative leaf area expansion rates (R_a), leaf area partition coefficients (LAP), and leaf area ratios (LAR). In all four species, R_w, R_a, and NAR decreased with decreasing growth irradiance, while LAP and LAR increased. Within each species, R_w was positively correlated with NAR but negatively correlated with LAP and LAR. In comparisons among the four species within each growth irradiance, R_w was positively correlated with LAP. We discuss the relationship between LAP and LAR and show that LAP = (R_a/R_w) (LAR).     

Variation in relative growth rate of 20 Aegilops species (Poaceae) in the field: The importance of net assimilation rate or specific leaf area depends on the time scale

Field experiments reporting the relative growth rate (RGR) patterns in plants are scarce. In this study, 22 herbaceous species (20 Aegilops species, Amblyopyrum muticum and Triticum aestivum) were grown under field conditions to assess their RGR, and to find out if the differences in RGR amongst species were explained by morphological or physiological traits. Plants were cultivated during two months, and five harvests (every 13–19 days) were carried out. Factors explaining between-species differences in RGR varied, depending on whether short (13–19 days) or longer periods (62 days) were considered. RGR for short periods (4 growth periods of 13–19 days each) showed a positive correlation with net assimilation rate (NAR), but there was no significant correlation with leaf area ratio (LAR) (with the exception of the first growth period). In contrast, when growth was investigated over two months, RGR was positively correlated with morphological traits (LAR, and specific leaf area, SLA), but not with physiological traits (NAR). A possible explanation for these contrasting results is that during short growth periods, NAR exhibited strong variations possibly caused by the variable field conditions, and, consequently NAR mainly determined RGR. In contrast, during a longer growth period (62 days) the importance of NAR was not apparent (there was no significant correlation between RGR and NAR), while allocation traits, such as LAR and SLA, became most relevant.     

GarlicESTdb: an online database and mining tool for garlic EST sequences

Background  

Allium sativum., commonly known as garlic, is a species in the onion genus (Allium), which is a large and diverse one containing over 1,250 species. Its close relatives include chives, onion, leek and shallot. Garlic has been used throughout recorded history for culinary, medicinal use and health benefits. Currently, the interest in garlic is highly increasing due to nutritional and pharmaceutical value including high blood pressure and cholesterol, atherosclerosis and cancer. For all that, there are no comprehensive databases available for Expressed Sequence Tags(EST) of garlic for gene discovery and future efforts of genome annotation. That is why we developed a new garlic database and applications to enable comprehensive analysis of garlic gene expression.     

Random amplified polymorphic DNA (RAPD) markers for genetic analysis inAllium

RAPD analysis was applied to onion (Allium cepa) and otherAllium species in order to assess the degree of polymorphism within the genus and to investigate if this approach was suitable for genetic studies of onion. Seven cultivars ofA. cepa, including shallot, and single cultivars of Japanese bunching onion (A. fistulosum), chive (A. schoenoprasum), leek (A. ampeloprasum), and a wild relative of onion (A. roylei), were evaluated for variability using a set of 20 random 10-mer primers. Seven out of the twenty primers revealed scorable polymorphisms between cultivars ofA. cepa and these will be further evaluated for use in genetic mapping. Wide variations in banding profiles between species were observed with nearly every primer tested. These were assessed for use in systematic studies within the genus. Ninety-one band positions were scored (+/-) for all the cultivars studied. Genetic distances between each of the cultivars were calculated and cluster analysis was used to generate a dendrogram showing phylogenetic relationships between them. The resulting analysis was in broad agreement with previous classifications of the species studied, confirming the validity of the method. However, amongst the species studied, it placedA. roylei as the closest relative ofA. cepa, questioning the current classification of the former species in the section Rhizideum.     

Effect of temperature on development and activity periods of the leek moth Acrolepiopsis assectella Zell. (Lep., Acrolepiidae)

Effects of temperature on egg, larval and pupal developmental times of the leek moth were examined at five constant temperatures ranging from 12 to 20°C. Using this data, a linear degree-day model for the leek moth was developed. The model gave the threshold temperature of T _h =6°C, and 630 degree-days were required above the threshold temperature, to complete the development of the leek moth. To validate the model in the field, flight activity during the summers of 1998 and 1999 was studied using pheromone traps. If the summer is warm the leek moth can have two generations per year in Sweden, but the probability of completing two generations within leek plantations is very limited. The likelihood of the leek moth becoming a pest is highly dependent on access to alternative host plants for the first generation of leek moths.     

Changes in Net Assimilation Rate and Leaf-area Ratio with Time in Dactyl is glomerata L.

Two natural populations of Dactylis glomerata, one from Norwayand the other from Portugal, were grown at four temperaturesin a 16-h photoperiod. Seedlings were harvested at six equalintervals of 7 days at 5 and 10 °C, and 3.5 days at 20 and30 °C. Time curves of net assimilation rate (NAR), leaf-arearatio (LAR) and other growth attributes were derived from curvesfitted to loge leaf area and loge plant weight as functionsof time. Three types of curves were found for both NAR and LARand these conformed to theoretical expectations. There was ageneral decline in NAR and LAR with time, but in certain treatmentsNAR increased during the later harvests, and the possible reasonsfor this are discussed. A similar rise in NAR was also obtainedin an experiment with 12 harvest times.     

Aspects of interspecific hybridization within edible <Emphasis Type="Italic">Alliaceae</Emphasis>

Crossing experiments within the genus Allium have been carried out for many years. Usually, with the aim of widening genetic variation, edible Alliaceae such as bulb onion, Japanese bunching onion, leek, garlic and shallot have been crossed with each other or with distant vegetable Allium crops. Interspecific hybridization, especially with wild relatives is considered as the best way of introgression desirable traits to the crops. By using sexual or somatic hybridization, many important characters, such as: disease and pest resistance, important metabolites and cytoplasmic male sterility have been transferred to other Allium crops. This review summarises some aspects of the directions of interspecific hybridization in edible Alliaceae and the significance and perspectives of using these hybrids in breeding programmes.     

Interspecific Variation in RGR and the Underlying Traits among 24 Grass Species Grown in Full Daylight

Abstract: A growth analysis was conducted with 24 central European grass species in full daylight to test whether traits underlying interspecific variation in relative growth rate (RGR) are the same in full daylight as they are at lower light, and whether this depends on the ecological characteristics of the studied species, i.e., their requirements with respect to nutrient and light availability.
In contrast to studies with herbaceous species at lower light, net assimilation rate (NAR) contributed more than leaf area ratio (LAR) or specific leaf area (SLA) to interspecific variation in RGR. This was associated with a larger interspecific variation in NAR than found in experiments with lower light. Without the two most shade-tolerant species, however, the contribution of LAR and its components to interspecific variation in RGR was similar or even higher than that of NAR.
Leaf dry matter content correlated negatively with RGR and was the only component of LAR contributing in a similar manner to variation in LAR and RGR. There was a positive correlation between NAR and biomass allocation to roots, which may be a result of nutrient-limited growth. RGR correlated negatively with biomass allocation to leaves. Leaf thickness did not correlate with RGR, as the positive effect of thin leaves was counterbalanced by their lower NAR.
Low inherent RGR was associated with species from nutrient-poor or shady habitats. Different components constrained growth for these two groups of species, those from nutrient-poor habitats having high leaf dry matter content, while those from shady habitats had thin leaves with low NAR.