In tea breeding, the relationship between seed weight and growth after germination has implications for the selection of hybrid seedlings. We found that the seed weight was positively correlated with the fresh shoot weight of 6-month-old seedlings. No relationship was observed between the seed weight and the number of seeds per fruit in some of the populations derived from natural crosses. Both seed and pollen parents influenced the weight of F₁ seeds. The influence of the pollen parent on the seed weight resembled xenia, a genetic effect of endosperm (3n). However, since tea seed is exalbuminous, and the cotyledons of the embryo occupy most of the volume and weight of the mature seed, the phenomenon of “pseudo-xenia” that we observed might correspond to the effects of the F₁ embryo (2n). Both seed and pollen parents also influenced the number of days until the emergence of F₁ seed. However, the seed weight did not play a major role in the time of emergence. Our results indicate that tea seed weight and the number of days until emergence are controlled independently by genetic factors of both seed and pollen parents.

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A clayey canal tends to be selected over a concrete-lined canal to achieve water quality conservation in a land improvement project. Therefore, it is important to analyze quantitatively the interaction of nutrients on the sediment in a clayey canal. In this paper, the COD, nitrogen and phosphorus fluxes as well as elution and removal rates across/on the sediment surface were estimated based on hydraulic model experiments. The experiments were carried out for water under aerobic conditions at 30–32^oC (CASE 1) and 6–9^oC (CASE 2). In CASE 1, the net COD elution rate and the net phosphorus elution rate were 8.2 mg·m^–2·day^–1 and 11.5 mg·m^–2·day^–1, respectively. Nitrogen was removed by nitrification on the sediment surface so that the net removal rate which is composed of the denitrification rate, the settling rate and the elution rate was 15.1 mg·m^–2·day^–1. The rate constant in which the nitrogen removal is expressed as a first-order kinetic was 0.010 m/day. In CASE 2, the net COD elution rate and the net phosphorus elution rate were 9.9 mg·m^–2·day^–1 and 5.4 mg·m^–2·day^–1, respectively. The net nitrogen removal rate and its rate constant were 9.0 mg·m^–2·day^–1 and 0.0023 m/day, respectively. The rates of elution and removal increased remarkably with the temperature.

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Recently, environmental conservation has been considered to be a more important part of the design of irrigation barrages than before. In this study, we investigated the spatial patterns of local flow velocity,etc. in a fishway with orifices (hereafter referred to as “orifice fishway”) to improve the performance for fish migration. The results showed that an orifice fishway enabled to achieve a more convenient maintenance through the use of a short baffle span and to obtain short migration routes for various fish species on a steeper slope of 1:4.5 and with a lower discharge of 0.12 m³/s compared with most of the currently used fishways by the improvement of “partially superimposed orifices”, even if the upstream or downstream water level changed.

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In recent years there has been an increasing activity related to the preservation of living organisms　(biological diversity) worldwide. It is obvious that the long-term trends contributing to this movement include the deterioration of the natural environment in rural villages associated with the introduction of technology solely intended to boost yields along with the urbanization of daily life as a consequence of the remarkable progress in agricultural production technology achieved since World War II. This report describes, firstly the role of paddy field areas as fish habitats compared with natural rivers, secondly the classification of fishes into several groups from the viewpoint of migration.And also it describes the influences of the present paddy field irrigation systems on fish habitat and forecasts future trends in this area.

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Medaka (Oryzias latipes) populations have recently declinedto such alevel that they are listed as a species in danger of extinction in the Red Data Book. And a decline in the numbers of catfish and loach has been reported in various parts of Japan. One cause of their decline is the increase in the drop height between paddy fields and water channels, particularly drainage channels. For catfish, loach,and medaka, paddy fields are important spawning grounds or habitats. This report describes the results of a study conducted by the construction of an experimental fishway that fish can use to migrate into an idle paddy field beside Lake Kasumigaura and for the observation and determination of the actual migration of fish swimming through the fishway during a 2-year period from 1997 to 1998. It was observed that immediately after the opening of the sluice gate between Lake Kasumigaura and the channel, the number of fishes migrating to the experimental site, which were assumed to have been carried by water flowing from the Lake, reached a peak.

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Based on statistical data such as the number of cattle head, the amount of raw milk production and demand, regional and monthly quantity of raw milk production, etc., the characteristics of dairy farming in Thailand were outlined. It is suggested that feeding of good-quality silage throughout a year is the most effective method to increase the amount of raw milk production in Thailand. However, the difficulty in making good-quality silage in Thailand was pointed out from the results of analyses of the microbial flora of the silages prepared in Thailand. Therefore, the selection of suitable lactic acid bacteria by using an evaluation system of lactic acid bacteria for silage-making in Thailand was proposed.

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Seedling appearance, survival and flowering of Trifolium pratense from naturally deposited seeds in meadow soil layers were monitored over a period of 8 years in a meadow for herbage cutting (hereafter referred to as “cutting meadow”) in the central mountainous district of Japan. In the meadow, Phleum pratense predominated and herbage had been harvested for making hay or silage in early June and late August of a year since the establishment of the meadow in 1966. T. pratense seedlings appeared from March to May (namely spring cohort) and from September to November (namely autumn cohort) every year. Estimated seedling density ranged yearly from 18 to 1,215 seedlings/m² in the spring cohorts and from 1 to 245 seedlings/m² in the autumn cohorts, with an average of 199 and 86 seedlings/m², respectively. Half-life ranged yearly from 4 to 63 days for the spring cohorts and from 33 to 248 days for the autumn cohorts, with an average of 42 and 135 days, respectively. Of the 13,485 seedlings marked, no individuals survived for more than 4 years. Most of the individuals undergoing flowering (hereafter referred to as “flowering individuals”) originated from the autumn cohorts. Thirty-two percent of the survivors began to flower in the first summer after their appearance. Ratio of flowering individuals to survivors rose to 81% in the second summer and fell to 50% in the third summer. It was suggested that during mechanical operations for harvesting in late August, T. pratense seeds were dropped and that the lack of third harvesting prolonged the half-life of the autumn cohorts which had succeeded in reproducing in this meadow.

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