1. The behaviour of nectar-collecting Bombus hypocritu sapporensis Cockerell queens was observed on a population of a spring ephemeral plant Corydulis umbiguu Cham. et Schlecht.2. Daily patterns of activity and behaviour changed with the progress of flowering. Activity peaked shortly before sunset early in the flowering season but approximately at noon towards the end of flowering. In the peak flowering period the queens tended to visit nearby plants and to change direction often, whereas early or late in the flowering period they flew further between visits and were less likely to change direction.3. Each plant was visited 0 to 24 times (mean 9.4 +SD 5.2) by the queens during the whole flowering season.4. The queens collected nectar, rarely through the front of the flowers but mostly through the spurs perforated by themselves or predecessors. At the beginning of the flowering season the illegitimate foragers often visited the front of the flowers before moving to the spurs; later, most queens quickly learned to land directly on the spurs. 5. Even the 59.7% of plants that were visited only by illegitimate foragers set seeds. Close observation confirmed that the illegitimate foragers opened the inner petals enclosing anthers and stigma frequently when visiting the front of the flowers before robbing, or occasionally when walking about on the flowers or collecting nectar through the perforated spurs.

Volatile substances emitted from the flowers of eight Magnolia taxa (M. sieboldii ssp. japonica, M. praecocissima var. praecocissima and var. borealis, M. tomentosa, M. salicifolia, M. obovata, M. denudata, and M. grandiflora) and one Michelia species (M. compressa) (Magnoliaceae) were examined and identified using GC‐MS. Volatile substances of these Magnolia and Michelia species consist primarily of monoterpenoids and sesquiterpenoids produced by the mevalonate pathway, acetogenins by the acetate‐malonate pathway, and phenyl‐propanoids by the shikimate pathway. These Magnolia and Michelia species all possessed various combinations of volatile monoterpenoids, acetogenins, and phenylpropanoids, except for Magnolia obovata, which emitted primarily sesquiterpenoids. Free amino acids in pollen of 12 Magnolia and one Liriodendron species were also analyzed, and their value as food sources for pollinators evaluated. Pollinators visiting the flowers of five Magnolia species were collected in their native sites and identified. Their behaviors and roles as pollinating agents were assessed.

Seasonal changes in several forms of nitrogen were investigated in the evergreen chamaephyte Pachysandra terminalis Sieb. et Zucc. growing in temperate evergreen coniferous forest. After plants sprouted new shoots, nitrogen accumulated largely as proteins in the leaves from summer to late autumn and, additionally, during a short spring period in the following year. Proteins accumulated in the overwintered leaves decreased markedly in summer, indicating that they were used for new shoot growth. A similar change was found in Fraction 1 protein. This is consistent with the seasonal changes in photosynthetic capacity and carboxylation efficiency observed in previous studies. The allocation of nitrogen to Fraction 1 protein increased in the spring, presumably to utilize better the relatively high light intensity at the forest floor before leaf expansion of the understory deciduous plants. In contrast to protein nitrogen, soluble nitrogen was present largely in stems and rhizomes. Aspargine was the major component of the amino acid pool in all organs throughout the year, especially in stems in summer. Since asparagine has the highest N:C ratio (2N:4C), an amino acid pool dominated by asparagine is economic in the use of carbon and advantageous for the carbon‐limited environment of the forest understory.

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Plasticity in growth, reproductive energy allocation (RA), reproductive output (PN), propagule weight (Pw), fecundity, and relative cost of producing single propagules (RA) and their interlinked properties were critically investigated in two grass species, Oryza sativa L. ev. Akihikari and Coix ma‐yuen Roman., grown under varying densities and soil nitrogen levels. In these two species, exceedingly marked plastic but parallel responses were detected in all significant yield and reproductive traits under changing growing conditions. The results obtained also corresponded very well with those for Coix ma‐yuen, Helianthus annuus and Glycine max reported in our previous works in this series (Kawano and Hayashi, 1977; Kawano and Nagai, 1986; Nagai and Kawano, 1986). In Oryza sativa, plants cultivated at higher densities exhibited proportionately lower individual biomasses, lower seed outputs, and smaller grain size in response to increasing density, although RA remained more or less constant throughout all five different densities, and fecundity showed an abrupt decrease in the overcrowded cohort beyond 400 plants/m2. In this experiment, Coix ma‐yuen was grown only under conditions of extraordinarily overcrowded density (over ca. 4,500 plants/m2) with extremely broad nitrogen fertilizer levels from 20 N (20 kg ammonium sulfate/10 ARE) to 100 N (100 kg/10 ARE). This species likewise demonstrated a remarkably sharp responsive plasticity in significant reproductive parameters with increasing N‐levels, just as was found with changing density (Kawano and Hayashi, 1977). One common significant conclusion obtained from the present series of studies was that sexual propagule production under limited resource availability—for example, a sharp decline in solar radiation and soil nutrients, due to strong interference in higher density plots—is exceedingly costly, implying that there occurs a significant change and variance in this important fitness component under changing environmental conditions. This was most conspicuously demonstrated by a very sharp increase in relative energy partitioning to a single propagule in response to increased density and decreasing nitrogen levels, the relative energy cost to a single seed (RA) increasing from 1.00 to 31.02, and from 1.00 to 10.31 in both paddy field and pot populations of Oryza sativa cv. Akihikari, respectively, and from 1.00 to 4.23 in field populations of Coix ma‐yuen. The adaptive significance of induced changes in several reproductive traits under changing environmental conditions was also discussed in the light of all the evidence available today.