Agar properties of two species of Gracilariaceae from the Gulf of California,Mexico

Agar properties of two potentially commercial important seaweeds from the Gulf of California were studied. Maximum yield in Gracilaria vermiculophylla (45.7%) occurred during the summer months, coinciding with high water temperatures (31°C) whereas minimum yields (11.6%) were obtained during the coldest months of the year when populations of this species diminish in the bay. Gracilariopsis longissima showed two yield peaks, one in spring and another in fall, before the maximum and minimum seawater temperatures. Gel strength in native agar from the two species was low (<22.5 g cm⁻²) for most of the year. G. vermiculophylla native agar showed a slight increase in gel strength from June to August, which were the hottest months. Maximum value was 85 g cm⁻¹ in August. Maximum gel strength in G. longissima was observed in October (91 g cm⁻¹), and an unusual native agar with no detectable gel strength was observed in March and April samples. Gelling temperatures range from 27.7 to 36.5°C in G. vermiculophyla and from 26.6 to 34.9°C in G. longissima, meanwhile melting points were 73.9 – 53.5°C and 75.5 – 56.6°C, respectively. Sulfate content was high, 6.3–13.9% in G. vermiculophylla and 1.9–11.9% in G. longissima, and on the other hand 3,6 anhydrogalactose content was low 12.1–26.7% and 9.1–23%, respectively compared to other species. Results obtained showed that mean native agar yields of Gracilaria vermiculophylla and Gracilariopsis longissima from the Gulf of California are comparable to other tropical Gracilaria. However, the low gel strength, high sulfate content and low 3,6 anhydrogalactose content observed in the native agar extracted from these species make this an agaroid, thus alternative methods of extraction should be used to evaluate the possibility of commercial utilization of both species.     

A study of the macro-environment at BenCat in southern Vietnam

Based on the meteorological data over a period of 4 years (1980–3), the macro-environment of BenCat Farm situated in the southern part of Vietnam (27 m above mean sea-level, 11° N and 106° E) was categorized as a “monsoon tropical climate”, due to heavy rainfall (annual mean 2028.96 mm) and about 32% wet days (annual mean 116.52 days) together with high air temperature (annual mean daily temperature 28.58, max. 32.33 and min 24.85° C). April was the hottest (monthly mean >35°C) and January the coldest month (monthly mean <22° C) of the year. The maximum number of wet days were during September and October (mean 18 days.month), whereas the minimum number of wet days were during January and February (mean <1 day/month). The months of December and January at Ben-Cat buffalo farm were categorized as the “comfortable (moderate-Dry) period” as the mean daily temperature was <27° C, while the remaining 10 months of the Calender year (February–November) were categorized as the “hot period” (mean daily temperature >27° C). On the basis of rainfall and the number of wet days, the hot period was further subdivided into a “hot-dry period” (February–April, mean of 1.67 wet days/month and mean rainfall 19.43 mm/month) and a “hot-humid period” (May–November, mean of 15.57 wet days/month and mean rainfall 276.28 mm/month).     

Photosynthesis, temperature and radial growth of Scots pine in northern Finland: identifying the influential time intervals

We analyzed the statistical dependence between temperature, the state of functional substances (S), estimated photosynthetic production and the radial growth of Scots pine in northern Finland. Annual sums of these variables were calculated for intervals consisting of consecutive calendar days. For daily mean temperature, all possible intervals between 1 April of the previous year and 31 August of the current year were tested. For S and the daily photosynthetic production, the tested range included days from April to October of the previous year and from April to August of the current year. These sums were compared with tree-ring indices using the Pearson correlation coefficient over the period 1906–2002. The highest correlations (r = 0.64) between daily mean temperature and growth indices were obtained for current-year periods starting 22 June and ending 28 July. For S, a temperature-derived variable describing the instantaneous photosynthetic capacity of Scots pine, the respective interval was from 5 July to 31 July (r = 0.63). The daily photosynthetic production of Scots pine was estimated for 1906–2002 using the PhenPhoto model. The interval during which the estimated daily photosynthetic production of Scots pine produced the highest correlation with growth indices (r = 0.56) was from 5 July to 27 July. Previous-year values of each variable were also significantly correlated to annual growth indices. The intervals with highest correlations were in May–June for each variable, and the correlations were rather low—between 0.3 and 0.4. We also tested selection criteria based on intervals that do not consist of consecutive calendar days, but results did not show notable improvements over the customarily used continuous intervals.     

Experimental investigation on weather cues for mast seeding of Fagus crenata

Although a recent study has suggested that the minimum temperature from late April to mid-May in the year preceding flowering causes mast seeding in Fagus crenata, no direct evidence is available to support this finding. The aim of the present investigation was, therefore, to test – in a field experiment – whether the minimum temperature determines mast seeding in F. crenata. We examined the effect of nighttime temperatures on flower-bud initiation in F. crenata by enclosing fruit-bearing branches in heated bags at night, thereby maintaining average nighttime temperatures of approximately 2°C above the ambient temperatures. Heating was applied at night from 21 April to 20 May, 21 May to 19 June, and 21 April to 19 June in 2001. Female inflorescence initiation was inhibited by the nocturnal heating in the period 21 April to 20 May and 21 May to 19 June. However, nocturnal heating from 21 April to 20 May was the more important based on the odds ratio of the former being much lower than that of the latter in a logistic regression model. Male inflorescence initiation was also inhibited by nocturnal heating from 21 April to 20 May. We therefore conclude that flower-bud initiation in F. crenata was controlled by nighttime temperatures between 21 April and 20 May.     

Day length and evening temperature predict circannual variation in activity duration of the colony of the Indian cliff swallow,Hirundo fluvicola

In avian species, circannual rhythms, in a number of biological variables, including locomotor activity, have been studied under both laboratory and natural environmental conditions. However, information on circannual rhythm in daily activity duration of Indian cliff swallow (Hirundo fluvicola) is not available. It is a communal mud nesting, non-migratory species and inhabits low under arch bridges. Although it figures in the IUCN Red List under the least concerned category, it is important to study its behavioral ecology that may be of utmost importance from conservation stand point. In the present investigation, we examined the circannual rhythm in daily activity duration in this species at a communal roosting site under Kharoon river bridge on the Raipur–Bhilai highway (21°15′07.54′′N; 81°32′30.65′′E), Raipur, India, for eight consecutive days, every month from August 2009 to October 2011. On each study day, observations were made in two sessions, morning and evening. We monitored and recorded emergence time of the first bird from the nest in the morning and entry time of the last bird to the nest in the evening. We also recorded the ambient temperature and humidity of the study site simultaneously. Average daily activity duration (the time difference between the first bird’s emergence time and the last bird’s entry time from/to the nest, respectively) was computed for each month. A significant circannual rhythm in activity duration was validated. The peak of activity rhythm occurred on 22nd June with a spread between 19th June and 25th June. The activity duration was the shortest in winter and the longest in summer. The daily activity duration was positively correlated to the day length, sunset time, and morning and evening temperatures; whereas negatively correlated with the sunrise time, and morning and evening humidity. The multiple linear regression models suggest that day length alone explains 96% of the total variance in activity duration, whereas only 0.5% variance was attributable to evening temperature. We conclude that the day length is the strongest predictor of circannual variation in daily activity duration of the colony of Indian cliff swallow; whereas the evening temperature has very little effect. Further, we recommend that comparable studies under natural conditions might be very helpful to explore the effect of environmental cues on other intriguing behavioral decisions made by this and other avian species.     

A phase response curve for circannual rhythm in the varied carpet beetle <Emphasis Type="Italic">Anthrenus verbasci</Emphasis>

We know that entrainment, a stable phase relationship with an environmental cycle, must be established for a biological clock to function properly. Phase response curves (PRCs), which are plots of phase shifts that result as a function of the phase of a stimulus, have been created to examine the mode of entrainment. In circadian rhythms, single-light pulse PRCs have been obtained by giving a light pulse to various phases of a free-running rhythm under continuous darkness. This successfully explains the entrainment to light-dark cycles. Some organisms show circannual rhythms. In some of these, changes in photoperiod entrain the circannual rhythms. However, no single-pulse PRCs have been created. Here we show the PRC to a long-day pulse superimposed for 4 weeks over constant short days in the circannual pupation rhythm in the varied carpet beetle Anthrenus verbasci. Because the shape of that PRC closely resembles that of the Type 0 PRC with large phase shifts in circadian rhythms, we suggest that an oscillator having a common feature in the phase response with the circadian clock, produces a circannual rhythm.     

An experimental study of the plastic responses of Ranunculus peltatus Schrank to four environmental parameters

The impact of four environmental parameters (water depth, type of substratum, current velocity and light intensity), on Ranunculus peltatus morphology and reproduction was tested in four 1 month semi- controlled experiments. Four development stages were underlined from April to August 2001 in R. peltatus: an elongation stage (April–June), a flowering stage (May–June), a fragmentation stage (June–July) and a potential regenerative stage (July–August). Water depth was therefore tested on R. peltatus elongation, type of substratum on R. peltatus elongation and flowering, current velocity on R. peltatus fragmentation and light intensity on its possible regeneration. The maximum development was measured for a 32 cm water depth. Current velocity did not have a significant effect on R. peltatus fragmentation. Regeneration depended strongly on light availability. This stage occurred only for unshaded or 50% shaded plants. Darkness prevented plants from regrowing.     

Resetting of the circannual rhythm of the varied carpet beetle Anthrenus verbasci by low‐temperature pulses

The varied carpet beetle Anthrenus verbasci L. has a circannual pupation rhythm and pupates in the spring in the wild. The change in photoperiod acts as a predominant zeitgeber for this rhythm. However, it is unclear whether the change in ambient temperature acts as a zeitgeber. The present study examines the effects of low‐temperature pulses on this circannual rhythm by exposing larvae kept under constant short‐day conditions (LD 12 : 12 h) at 20 °C to a lower temperature of 15, 10 or 5 °C for 8 or 12 weeks at various phases. Larval development and pupation are suppressed during exposure to low temperature, with this pupation being induced in sufficiently grown larvae within 2 months of a return to 20 °C. These results are attributed to the exogenous suppression and stimulation of pupation, rather than being related to the circannual rhythm (i.e. masking of the circannual rhythm by temperature). Furthermore, long‐term observations demonstrate the existence of phase‐dependent phase shifts of circannual rhythm as a result of low‐temperature pulses. Circannual phase response curves to low temperature are constructed on the basis of the phase shifts obtained. A low‐temperature pulse as a winter signal can reset the circannual rhythm of A. verbasci. It is probable that both temperature and photoperiod play a role in the entrainment of this circannual rhythm to a natural year.     

Reproduction of plateau pika (<Emphasis Type="BoldItalic">Ochotona curzoniae</Emphasis>) on the Qinghai–Tibetan plateau

The reproduction of the plateau pika (Ochotona curzoniae) was investigated in Guoluo District at an elevation of 4,000 m on the Qinghai–Tibetan plateau, China, from April 2007 to August 2008. Reproduction was seasonal, and the breeding season lasted from April to late June/early July. Adults produced two litters in each year, and the mean litter size, estimated by counting the number of embryos in utero, was 3.3 ± 0.1 (n = 52) in 2007 and 3.2 ± 0.1 (n = 66) in 2008. The timing of reproduction showed high inter-annual variation; lower precipitation and the concomitant delay in spring vegetation phenology may have retarded the onset of the breeding season in 2007 compared with 2008. The most frequent litter sizes were 3 and 4, which together comprised 71.2% and 83.3% of litters in May and June of 2007 and 2008, respectively. Compared with previous studies, reproduction was highly variable between geographic areas. Pikas produced between one and five litters per year in different regions of the plateau over different breeding seasons. This geographic and inter-annual variation appeared to be associated with the duration of plant growth at each site, suggesting that plateau pikas adjust the length of their breeding season to match the period when sufficient energy is available to support the high energy demands of reproduction.     

Tree-ring variation,wood formation and phenology of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) from a representative site in Slovenia,SE Central Europe

Long-term variation in tree-ring widths (1873–2006) and intra-annual dynamics of cambial activity and tree-ring formation in 2006 were studied in mature beech (Fagus sylvatica L.) trees at a typical forest site near Ljubljana (46°N, 14°40′E, 400 m a.s.l.) and related to leaf phenology and climate data. Tree-ring widths were negatively affected by minimum March and maximum August temperatures and favoured by May and July precipitation. Precipitation of the previous August and temperature of the previous November also had a positive effect. Leaf unfolding was affected by March and April temperatures, occurring later if they were low. Leaf yellowing was positively affected by minimum July temperatures and negatively by September precipitation. In 2006, leaf unfolding occurred on 16 April and was immediately followed by reactivation of cambium at breast height of the trees. One week later, the cambium obtained its maximum width (around 11 cell layers) and the rate of division increased until the end of May/beginning of June. By the end of June, 75% of the tree-ring was formed. Cambial cell divisions stopped from the end of July to mid-August. The average time of cambial activity was 100 days. Leaf yellowing occurred at the end of October, i.e. nearly 2 months after the cessation of cambial cell division. We discuss the usefulness of a combination of long-term (tree-ring width and phenology) and short-term (wood formation at a cellular level) data to understand better the environmental signals registered by a tree during growth.     

The response of <Emphasis Type="Italic">Corylus avellana</Emphasis> L. phenology to rising temperature in north-eastern Slovenia

Knowledge of plant–weather relationships can improve crop management, resulting in higher quality and more stable crop yields. The annual timing of spring phenophases in mid-latitudes is largely a response to temperature, and reflects the thermal conditions of previous months. The effect of air temperature on the variability of hazelnut (Corylus avellana L.) phenophases (leafing, flowering) was investigated. Meteorological and phenological data for five cultivars were analysed over the periods 1969–1979 (P1) and 1994–2007 (P2) in Maribor, Slovenia. Phenological data series were correlated strongly to the temperature of the preceding months (R ²: 0.64–0.98) and better correlated to daily maximum and mean temperatures than to daily minimum temperatures. About 75% of phenophases displayed a tendency towards earlier appearance and a shorter flowering duration during P2, which could be explained by the significant temperature changes (+0.3°C/decade) from December to April between 1969 and 2007. An increase in air temperature of 1°C caused an acceleration in leafing by 2.5–3.9 days, with flowering showing higher sensitivity since a 1°C increase promoted male flowering by 7.0–8.8 days and female flowering by 6.3–8.9 days. The average rate of phenological change per degree of warming (days earlier per +1°C) did not differ significantly between P1 and P2. An estimation of chilling accumulation under field conditions during 1993–2009, between 1 November and 28 February, showed that all four of these months contributed approximately similar amounts of accumulated chilling units. The growing degree days (GDD) to flowering were calculated by an estimated base temperature of 2°C and 1 January as a starting date, given the most accurate calculations. In general, thermal requirements were greater in P2 than in P1, although this difference was not significant. Longer-time series data extended to other agricultural and wild plants would be helpful in tracking possible future changes in phenological responses to local climate.     

Reproductive Strategies of <Emphasis Type="Italic">Trachypithecus pileatus</Emphasis> in Arunachal Pradesh,India

We studied reproductive behavior of free-ranging capped langurs (Trachypithecus pileatus) in the Pakhui Wildlife Sanctuary, Arunachal Pradesh, India. Four species of primates —Trachypithecus pileatus, Macaca mulatta, M. assamensis, and Nycticebus bengalensis— live there. We studied the mating seasons, mating frequency, copulatory attempts, time spent in copulation, and interval between 2 successive copulations, gestation length, and interbirth interval of 4 groups of capped langurs during 2001–2003. We observed 2 mating seasons in a year. The first was larger, comprising 5 months (September–January), and the second was short, April and May. Mating was intensive in the morning session (0600–1000 h); 57% of total mating events occurred then. The average gestation period was 200 d. November was the most favorable month for breeding. In a year, 107 mating events occurred involving 5 adult females. Average time per mounting attempt is 12 s. Duration of mounting was the maximum in November. Interbirth interval was 23 months and 10 d. The birth season was 129 days, December–April; 53% of births occurred in February and March. Average birth rate is 0.386 birth/female/yr.     

Quantifying food limitation of arthropod predators in the field

A method for quantifying food limitation of arthropod predators in the field is presented and applied to species of ground beetles (Carabidae) and sheet-web spiders (Linyphiidae) from a cereal field. Food limitation is expressed quantitatively as accumulated hunger (=starvation) by transforming 24-h food consumption at 20°C of animals newly collected in the field into days of starvation at 20°C. This is done by means of a reference curve relating 24-h food intake at 20°C to starvation periods (days) at 20°C. Such a reference curve was obtained for the carabid beetle Agonum dorsale in the laboratory. For other species the reference curve was modified with species-specific data. The procedure makes it possible to compare the feeding conditions of different species populations that are part of the same community. Hunger levels in the field for females of A.␣dorsale were equivalent to c. 15 days of starvation in early spring, c. 5 days in June, increasing to c. 10 days in late summer. Two ground beetles occurring during summer also showed increasing hunger levels from June to July, probably the result of a dry summer. Two spider species experienced a hunger level in the range of 4–8 days of starvation. Received: 15 August 1997 / Accepted: 22 January 1998     

Timing of larval release by Porites astreoides in the northern Florida Keys

 Annual and lunar patterns of larval release by the coral Porites astreoides in the Florida Keys were investigated. Corals were collected monthly and maintained in outdoor, flow-through systems to quantify nightly release of larvae. Planulae were released during a period from 10 days prior to the new moon through 11 days after the new moon, with a peak in release centered on the new moon. The average duration of larval release by a single colony was 9 nights. Although the correlation was low (r=0.292), there was a positive relationship between colony size and number of larvae released. The majority of larval release occurred in April and May, although smaller numbers of larvae were observed from June through as late as September. Larval release appeared to be correlated with the average water temperatures over the 30 days prior to the new moon, peaking when water temperatures were 24.5–27.5 °C. Accepted: 3 August 1998     

Seasonal changes in the territorial behaviour of the satyrine butterfly Lethe diana are mediated by temperature

The territorial behaviour of butterflies often changes with temperature. The satyrine butterfly Lethe diana has three generations a year, and males display territorial behaviour in the May–June and September–October generations, but not in the July–August generation. This study investigated the relationship between this seasonal change in mate-locating behaviour and thermoregulation. When L. diana was able to hold a territory, thoracic temperature ranged from 23.8 to 33.6°C. This temperature was mainly influenced by environmental temperature based on air temperature, solar radiation, and wind, and metabolic heat was estimated to increase thoracic temperature by about 5°C in the May–June generation. When environmental temperature at a territorial site was within this range of the thoracic temperature minus the metabolic heat (approximately 5°C), L. diana males held territories. Since territorial sites were selected irrespective of the temperature, L. diana could not hold a territory when the temperature of the territorial site exceeded the threshold. In July–August, the temperature of the territorial site was almost always above the suitable range. These results suggest that seasonal change in territoriality of L. diana is due to behavioural thermoregulation. Electronic Publication     

Some ecological parameters of Artemia parthenogenetica Gahai and their use in resource exploitation

The effects of temperature on population characteristics of Artemia parthenogenetica Gahai from the Gahai Salt Lake, Qinghai Province, China, were studied in the laboratory at a salinity of 60‰. The major conclusions are as follows: (1) It was found that the adaptive temperature for the development of brine shrimp ranged from 10°C to 39°C. The threshold temperature of development (TD) and the effective accumulative temperature (TA) for hatching were 9.94°C·d and (22.91±2.08)°C·d, respectively. The TD and TA for the larva were 10.33°C·d and (261.26±24.1)°C·d, respectively, and for the whole generation were 10.28°C and (458.68±57.60)°C·d, respectively. (2) It showed that the population’s net reproduction rate (R_o), the intrinsic rate of natural increase (r_m), the mean generation time (T), the finite rate of increase (λ), and the days for population to double (t) of the brine shrimp were determined over temperatures ranging from 19°C to 34°C by analyzing the life table and numerical model. In the temperature range of 14.3°C to 37.3°C for R_o>1, the optimum temperature (°C) for R_o, r_m, λ, and t were 25.8°C, 29.8°C, 30.5°C, and 29.02°C, respectively. The maximum values of R_o, r_m and λ were 54.86 ind., 0.106138/d, and 1.1070/d, respectively. The minimum value of t was 4.73 d. The value of T was in a range of 96.77 to 16.10 d. (3) Based on the 1993–1994 and 1997 data of the water temperature in the Gahai Salt Lake, Qinghai Province, it was estimated that the number of generation of A. parthenogenetica Gahai and the number of the reproductive peak value were 2.67±0.34 and 4.69±0.43 in a year, respectively. The peak of nauplii of the first generation was on April 20 to 28. The last whole generation began on August 10. The first reproductive peak was on June 18 to 25. The last reproductive peak was on September 12 to 17. The nauplii that hatched after September 1 cannot complete the development from nauplii to adults because of insufficient habitat effective accumulative temperature. During the period from July 11 to September 20, there was a relatively high productivity of the population. In this case, doubling the population would take less than 30 d, and the intrinsic rate of natural increase was over 0.02/d. Therefore, the value of resource exploitation would be maximal during that period annually.     

Effects of temperature on the development and circannual control of pupation in the carpenter moth, <Emphasis Type="Italic">Cossus insularis</Emphasis> (Lepidoptera: Cossidae), reared on an artificial diet

The effects of temperature on larval development and the timing of pupation in the carpenter moth, Cossus insularis (Staudinger) (Lepidoptera: Cossidae) were examined by artificial rearing under different temperatures and the same photoperiod (15L:9D). Although C. insularis pupated and emerged at 20, 25, and 30 °C, the pupation rate was lower at 20 °C than at 25 and 30 °C. These results suggest that the optimum temperature range for preadult development is 25–30 °C. The duration of larval development was about 260 days for the first pupation group at 25 and 30 °C, and at least 600 days at 20 °C. Therefore, the C. insularis generation time was 2 years or more, as the total effective temperature for development from hatching to the pupal stage was unlikely to be reached within 1 year in Tokushima Prefecture. The second group pupated at 25 °C, about 200 days after the first group. This periodicity of pupation was likely due to the free-running period of the circannual rhythm. Furthermore, although only the first group pupated at 30 °C, the peak was almost synchronous with the first group at 25 °C. These results indicate that the timing of the first pupation group in C. insularis is temperature compensated. Therefore we propose that the presence of an endogenous rhythm during the development of C. insularis is evidence for a circannual rhythm related to the timing of pupation.     

Mycosphaerella chaenomelis sp. nov.: The teleomorph ofCercosporella sp., the causal fungus of frosty mildew inChaenomeles sinensis, and its role as the primary infection source

A leaf spot disease called frosty mildew was observed onChaenomeles sinensis throughout Japan. Small brown spots with white tufts occurred followed by successive defoliation. On the fallen leaves, minute black dots are formed. The causal fungus was regarded as a new species ofMycosphaerella, M. chaenomelis, andCercosporella chaenomelis in anamorph. Pathogenicity of the fungus was confirmed only inC. sinensis by inoculation experiments. Colonies of the fungus grew well on potato sucrose agar, and grew at 10–30°C with an optimum temperature of 25°C. The fungus overwintered on the fallen diseased leaves in the form of pseudothecia, and ascospores served as the primary infection source from April to June.     

Effect of temperature on the survival and infectivity of <Emphasis Type="Italic">Pseudotheraptus devastans</Emphasis> vector

The aim of this study was to investigate under a controlled environment, the effect of temperature on the survival and infectivity of Pseudotheraptus devastans Distant, a cassava anthracnose disease vector. The insect P. devastans was collected from young cassava (Manihot esculenta Crantz) field plots, at the International Institute of Tropical Agriculture, (IITA), Ibadan, Nigeria. A mixture of the different developmental stages of eggs, first to fifth instar nymphs, and adults, were incubated in controlled environment chambers, under various constant temperatures of: 15, 17, 22, 25, 27, 30, and 35°C. Relative humidity at different temperature conditions were recorded and maintained at 90%, 85%, 80%, 75%, 70%, 65%, and 60%, respectively. A significant increase in insect survival was observed between 22 and 27°C temperature conditions while a significant decrease in survival was observed at 15°C and above 30°C. Lesion number, lesion diameter and infectivity among the insect stages varied as a function of temperature and relative humidity. Infectivity was highest at 22–25°C maintained at 75–80% RH and lowest at 15°C and above 30°C maintained respectively, at 65% RH and 90% RH. There was considerable low vector infectivity due to low survival of the insects at extreme temperatures.     

Gap-detecting mechanism in the seed germination ofMallotus japonicus (Thunb.) Muell. Arg., a common pioneer tree of secondary succession in temperate Japan

Germination responses ofMallotus japonicus (Thumb). Muell. Arg. seeds to temperature revealed a gap-detecting mechanism in the seed germination of the species. Among various constant and alternating temperatures examined in the range from 12–40°C, only very limited temperature regimes were found to be favourable for seed germination, specifically, alternating temperatures between 18–32°C and 28–40°C. A single several-hour higher-temperature (32–40°C) treatment could also induce the germination of seeds which had been imbibed for several days at a constant temperature in the range of 20–26°C, suggesting that there is a process requiring higher temperature among the overal germination processes. Seeds located at or near the surface of denuded soil would have a good chance of experiencing such a temperature change when several rainy days are followed by fine weather, while seeds beneath close vegetation would not. On the other hand, the pressence or absence of light or a simulated ‘canopy ligh’ had little effect on the germination. Therefore, it was concluded that the seeds ofM. japonicus have a ‘gapdetecting mechanism’ in the form of a higher-temperature requirement of a certain process involved in the overall germination processes.