In a T. repens-Z. japonica coexisting sward, seed reproduction of T. repens commonly occurs, so that new members frequently recruit into the adult population. How much variation is potentially supplied and which members of the seed population can recruit into the adult population, however, has been unknown. In this paper, we attempted to assess the amount and pattern of genetic variation within the seed population of T. repens in the coexisting sward. Following questions were addressed : (1) what amount and patterns of variations the seed population shows in seed reproductive characters ? (2) Is number of flower-heads per plant dependent on plant size? Plants derived from the seeds, which were collected from ten T. repens patches in the sward, were assessed using a common garden technique for seed reproductive characters. Large intra-population variations were found in almost all characters examined (number of flower-heads, flower-head size, peduncle length, longevity of flower-heads, the dates of first flowering and of last flowering, and the flowering duration). Census of flowering phenology showed the existence of a considerable variation in flowering pattern within the population, ranging from plants with short flowering duration to plants with extended durations. Number of flower-heads per plant showed no relationship with plant size ; larger plants did not always produce more flower-heads, and some of small plants produced many flower-heads. These findings showed that greatly different variants were potentially supplied to the adult population which confronted with the changing environment, and suggested the absence of size dependent flower-head production in T. repens.

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Competitive ability can be evaluated in the two distinctive ways : competitive effect, the ability to suppress other individuals and competitive response, the ability to avoid being suppressed. In this study, we examined variation in competitive effect and competitive response among fifteen cultivars of perennial ryegrass (Lolium perenne) and associated traits for a period of two years under sward conditions. A replacement series design with pure swards and equally proportional mixed swards with orchardgrass (Dactylis glomerata) was employed for each cultivar in order to assess competitive ability. Shoot and root morphological traits of each cultivar were also measured under pot conditions. Competitive effect and competitive response were evaluated by relative yield (RY) of D. glomerata and RY of L. perenne, respectively. The results obtained are as follows : (1) There were large differences in competitive effect and competitive response between the cultivars. The differences were more consistent in competitive effect than in competitive response, and in the second year than in the establishment year. (2) The cultivars which suppressed more D. glomerata in the mixture were less suppressed by D. glomerata. Tetraploid cultivars tended to show higher competitive ability than diploid ones. Particularly, the cultivar for turf use was least competitive. (3) The large proportion of variances in relative competitive ability between the cultivars were explained by seed size and morphological traits of shoot and root measured under pot conditions. The cultivars with larger seeds tended to have a higher competitive ability. Competitive ability showed conspicuous correlations with mean tiller weight and number of tillers rather than root and shoot dry matter weight (DM). The cultivars with few but larger tillers tended to have a higher competitive ability than those with more but smaller tillers.

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The voluntary intake and the digestibility of nutrients of water hyacinth silage prepared by mixing with defatted rice bran (DRB) or rice bran (RB) were investigated. Each silage included the additives at the rate of 15% of fresh matter, and was given to three Japanese Brown heifers ad libitum, respectively. The chemical component of the DRB and the RB-added silages were 9.5% of DCP and 2.2 Mcal/kg of DE in the former and 8.9% of DCP and 2.2 Mcal/kg of DE in the latter. The quality of both silages was high. Voluntary DM intake was 1.3% of body weight per day in the DRB-added silage and 0.9% in the RB-added silage. The digestibilities of DM were 50.3% for the former and 51.8% for the latter. The voluntary intakes of DM and DE were lower than the requirement for maintenance, but DCP intake was higher than the required.

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Changes in freezing tolerance (as measured by LT_<50>), water content and physical state of tissue water (as measured by the half-line width of proton spectrum), and dry weight of orchardgrass (cvs. Akimidori and Wasemidori), perennial ryegrass (cv. Reveille) and timothy (cv. Senpoku) were periodically determined from Aug. 1992 to Apr. 1993. All grasses began to harden by the end of September when minimum temperatures were below 10℃. LT_<50> values continued to increase since then to reach maximum by mid-winter. They were ranked in the following order : Senpoku (-28℃)>Wasemidori (-20℃)> Akimidori (-18℃) > Reveille (-14℃). The increase in LT_<50> values was accompanied by a decrease in water con-tent of crown tissues up to early November. However, LT_<50> values continued to increase from early November to mid-December without any reduction in water content. The half-line width of tissue water changed drastically during early November to reach nearly twice the value recorded previously. The development of freezing tolerance seems to involve two stages, the former involving a reduction in "free water" and the latter, with a change in the physical state of water and other biochemical transformations. Dry weight of plants increased linearly from mid-September in all grasses, but the time to reach maximum dry weight varied with the species. There was no increase in dry weight in timothy beyond 19 October, while orchardgrass and perennial ryegrass continued to accumulate dry matter up to 2 and 17 November, respectively. During winter, 30-50% of the crown tissues and more than 60% of shoots on the basis of dry weight were lost. Timothy lost the least amount and orchardgrass, the most.

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Photoinhibitory damage under chilling (10℃) or heat (35℃) condition with moderate light intensity was estimated by comparing chlorophyll fluorescence of detached leaves. Five cool season grasses showed higher chlorophyll fluorescence at 10℃ as compared to 6 warm. season grasses. Reversed result was obtained at 35℃. Cool season grasses showed severe leaching of chlorophyll at 35℃ with complete depression of chlorophyll fluorescence. As one of the protection mechanism, carotenoid content was measured after heat or chilling treatment. There was no clear relationship between chlorophyll fluorescence and carotenoids except when cool season grasses were subjected to 10℃, suggesting a possible involvement of carotenoids for photoprotection in these grasses at low temperature.

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Damage in leaves caused by moderate light coupled with low (10℃) or high (35℃) temperatures was estimated by comparing the changes of chlorophyll a fluorescence of leaves measured at room temperature. Detached leaves of twenty seven zoysiagrasses (4 species and hybrid types) were subjected to low or high temperature stress for 24h and 48h respectively, and the chlorophyll a fluorescence was measured after dark treatment. Fluorescence intensity was calculated as a percentage of chlorophyll a fluorescence of control measured before the temperature stress. Reduction of fluorescence intensity might suggest severe damage of PSII (photosystem II) that was observed clearly at low temperature as compared to that at high temperature in zoysiagrasses. Wide variations of fluorescence intensity was observed in zoysiagrasses both at low and high temperature stress. Zoysia tenuifolia showed the highest fluorescence intensities in average both at low and high temperature treatments, which is partially attributed to the narrow leaf blade with low light absorption. Carotenoid content in leaves showed better correlation with fluorescence intensity at 24 h than chlorophyll content in leaves in 17 strains of Z. japonca subjected to both low and high temperatures. It is suggested that carotenoid may play a protective role against photoinhibition in the leaves of Z. japonca at low temperature stress as well as at high temperature stress.

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The summed dominance ratio, SDR, has been used to explain the species dominance in grassland community studies. The SDR_2 for a given species is defined as the average of the following two quantities : (1) relative coverage and (2) relative plant height of each species to the respective maximum values in one community. Then, the SDR_2 takes a value between 100 and 0. Since this index cannot be used for comparing the vegetation among various communities, a new index, the extended summed dominance ratio, E-SDR_2, was developed and described in this paper. In the new index, the range for the selection of the maximum coverage or height in calculating the SDR_2 is extended from one community to all the related communities. We selected, as an example, a comparison between the E-SDR_2 and the SDR_2 calculated using date which had been accumulated in a semi-natural grassland with four different treatments in the Tohoku Area for 11 years. All the values of the SDR_2 for Miscanthus sinensis were 100 in every treatment in all the years, which the values of the E -SDR_2 for M. sinensis varied with the treatments or years and all were lower than 100. We concluded that the E-SDR was the available index for comparing the vegeattion among various communities which were calculated from the plural quantities like the SDR.

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Application of in vitro enzymatic technique by using both pronase and cellulase was investigated to estimate the digestibility of the herbage of both the native pasture composed of Miscanthus sinensis, Pleioblastus chino var. viridis and Arundinella hirta and the improved pasture composed of temperate grasses. For the native grasses, the in vitro dry matter degradability (IVDMD) was lower (p<0.001) than the in vivo dry matter digestibility (in vivo DMD) measured by total fecal collection (TFC) method. There was a positive significant correlation between the IVDMD and the in vivo DMD. In similar, there was the same relationship as the above between the IVDMD and the in vivo energy digestibility. On the other hand for the temperate grasses, there was no significant difference between the IVDMD and the in vivo DMD measured by the TFC method. Moreover, the relationships between the IVDMD and the in vivo digestibilities measured by acid-insoluble ash (AIA) index methed were considered for the herbage grazed in the improved pasture, since the recovery of AIA was about 100% in the TFC trial. A positive significant correlation was detected betweem the IVDMD and the in vivo energy digestibility measured by the AIA method.

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A grazing experiment was carried out to clarify the effects of additional paddock on the liveweight gain of Japanese shorthorn steers. Two groups of four Japanese shorthorn strees (similar weight and age of 7-3 months old) were grazed on only Lolium paddock until mid-season of late July when herbage growth rate was high, and from early August one group was allowed to have access to Loilium additional paddocks (Pe group) and another one was allowed to graze Festuca addtitonal paddock (Tf group). An allocated area per of Lolium paddock and additional paddock was in a 1 : 1 ratio. The range of daily mean gain per head in each year was 0.61-0.70 kg in Pe group and 0.49-0.68 kg in Tf group. Pe group tended to show a higher performance during the rearing stage of Japanese shorthorn steer than the Tf group. This tendency was attributed to high content of crude protein and high digestibility in herbage as well as sufficient total digestible nutrient intake rate of steers in Lolium additional paddock compared to Festuca additional paddock in latter half of the grazing season. The experimental results confirm that combination of Lolium additional paddock and Lolium paddock in a 1 : 1 ratio could achieve high performance of daily liveweight gain of Japanese shorthorn steer through grazing season, especially during summer and autumn.

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To develop a simple method of laboratory silage fermentation, we made several experiments of ensiling and a model system of ensilage by use of milled alfalfa hay cube added with water (AHC medium) and inoculated with a lactic acid bacterium (LAB), a butyric acid bacterium (BAB) and a coliform bacterium (CFB). In these experiments, we used plastic pouchs for anaerobic incubation instead of bottle silos and anaerobic jars and the following results were obtained. 1. The quality of the silage in the pouch was almost the same as that in the bottle silo when one lot of alfalfa was used as a plant material. 2. The quality of of the model system of ensilage was reproducible if incubation conditions were consistent. The standard diviation of that was below ±9%. Butyric acid was produced when the moisture content of AHC medium was 85%, but no butyric acid was produced when the moisture content of the medium was reduced to 70%. 3. When the moisture content of AHC medium was 85%, low soluble sugar content of the medium (less than 0.5%) and smaller inoculum size of LAB (10^6 cfu/g) than that of CFB (10^7 cfu/g) were effective for butyric fermentation. Under these conditions, multiplication of CFB was ob-served.

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The differences in salt tolerance between reed canarygrass (RCG) grown on soil perfused with urine(U-RCG) and on soil not perfused (C-RCG) were discussed in regard to the growth rate and the contents of cation and free amino acid. The seedlings grown on each soil were cultured in standard solution (KIMURA's B solution) for 10 days, then NaCl was applied to the solution to adjust its concentration to 0, 100 and 200 mM. Ten days after NaCl application, the plants were harvested to measure the weights and the contents of cations and free amino acid. The relative value of dry weight increase in plant tops during NaCl treatment to that during standard solution culture was used as an indicator of salt tolerance. 1. When the growth rates of U-RCG and C-RCG in standard solution were expressed as 100, the rate of U-RCG was higher than that of C-RCG at 200 mM NaCl (82 and 68), suggesting the stronger salt tolerance in U-RCG. 2. Sodium content of the plants increased, while K, Mg and Ca contents decreased with increasing NaCl concentrations in solution culture. The cation contents, especially K of plant tops in U-RCG tended to be higher. In U-RCG, the plant top/root ratios in Na, K, Mg and Ca contents were higher, and increased by the application of NaCl. 3. Total free amino acid contents of plant tops were increased by the application of NaCl. Though the contents were higher in U-RCG, the increase rates were higher in C-RCG. Proline content markedly increased in both RCGs and the Pro/total amino acid content ratio attained to 21.4% inU-RCG and 15.5% in C-RCG, being the highest at 200 mM NaCl. In roots, changes in free amino acid contents by the application of NaCl were different between U-RCG and C-RCG. However, no remarkable tendency of changes was shown.

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A method for determining nitrogen fixation activity of white clover in the field was examined, and seasonal variations of the activity were studied by acetylene reduction assay in a white clover-orchardgrass grassland with various rates of the mixing. The incubation for acetylene reduction assay was conducted in a transparent plastic chamber settled on an upper guard of a steel tube drived into the ground. All assays were carried out in 10% (v/v) acetylene concentration in air and for 30 min of a incubation time. The injection of acetylene gas and the collecting gas-sample were achieved using syringes through rubber-sealed ports of incubation chamber. The results suggest that this system is useful with some confidence for measuring nitrogen fixation activity of grassland under field condition. The acetylen reduction activity of white clover in the field appeared at the times except snowfall and seasonally changed with two peaks ; a large peak in late May and a small peak in late September except for the temporary fluctuations owing to harvesting and fertilizing. The grassland over 70% in coverage of whiteclover showed nearly the similar quantity of acetylene reduction activity as pure stand of white clover. In mixed stand, the acetylene reduction activity of white clover was promoted by accompanying with orchardgrass unless light condition on leaflets of white clover was deteriolated.

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