Relationship between in vitro digestibility and some morphological and physiological traits (Table 1) was investigated in aftermath (late August) of space-planted orchardgrass. Significant difference was observed when digestibility of eight varieties was compared with the mean (n=91-97 plants). Difference between the highest (Okamidori) and the lowest (kitamidori) was 8.0%. Range for 758 plants pooled varieties was 21.3% (Table 2). In the relationship between in vitro digestibility of aftermath and plant characters of hay (Table 5), higher digestibility plants showed less leaves and prostrate form (Kitamidori and Tenderbite), late ear emergence (Okamidori and Tammisto), and poor spring vigor (Chinook, kitamidori, Tammisto and Tenderbite). Using 758 plants, prostrate form, flexible leaves and later ear emergence were correlated with high digestibility. In the relationship between in vitro digestibility of aftermath and plant characters of aftermath (Table 4), higher digestibility plants showed prostrate form (Tammisto and Tenderbite) and greater leaf width (Akimidori, Okamidori and Tenderbite). Plant with less damage for diseases (mainly Rhynchosporium orthosporum and Scolecotrichum graminis) showed higher digestibility in all varieties studied. Using 758 plants, prostrate form and less diseases damage were correlated with high digestibility.

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To predict in vitro digestibility from some plant characters of orchardgrass plants, multiple regression analyses were done by the selected variables method in the following three ways. A) Estimation of hay digestibility from hay characters. B) Estimation of aftermath digestibility from hay characters. C) Estimation of aftermath digestibility from aftermath characters. Data derived from 758 plants of 8 varieties (n=91-97) were used to this calculation. Seven characters in hay and 8 characters in aftermath were investigated besides in vitro digestibility (Table 1). As the results of multiple regression analyses in each variety, significant multiple correlation coefficients were obtained in 6, 6, and 8 varieties in A, B, and C, respectively. Using 758 plants pooled 8 varieties, numbers of selected variable were 4, 6, and 8 characters, and multiple correlation coefficients were R=0.303, 0.354, and 0.375 in A, B, and C, respectively (Table 2-5). Judging from the value of standard regression coefficients and frequency of selected variables in multiple regression equations (Table 5), it is concluded that growth habit, leaf width and date of ear emergence in hay, and growth habit, degree of diseases, leaf color and vigor in aftermath were important characters affecting in vitro digestibility. Though significant coefficients were obtained through A to C, the values of the coefficients were comparatively low. More detailed investigation for important characters is required for getting effective multiple regression equations to predict in vitro digestibility of orchardgrass plants.

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The present studies were undertaken to elucidate the relationship between nitrogen concentration of leaf blade and photosynthesis in several tropical grasses. The grasses tested are shown in Table 1. Experimental plants were grown in 1/5000 Wagner pot with different levels of nitrogen fertilizer. The apparent photosynthesis rate was measured at radiation flux of 50klx, 20klx, and 10klx on the youngest fully expanded intact leaf in assimilation chamber. After measurement, area of the leaf and its dry weight were measured. Nitrogen percents based on dry matter of individual leaves were measured by the semimicro-Kjeldahl method. The results are summarized as follows ; In all species, positive correlation was observed between the photosynthesis rate and leaf nitrogen percent in the range of 0-5 percent in 1975. In experiments in 1976 where effects of wider range of nitrogen percent were investigated, the same relationships were recognized in the range of 0-5 percent of leaf nitrogen excepting the case of fall panic. However, at higher level of leaf nitrogen, different relations between nitrogen percent and photosynthesis rate were observed. The photosynthesis rate of African millet, Rhodesgrass, Guineagrass, coloured guineagrass, dallisgrass and bahia-grass tended to decrease in the high range of leaf nitrogen percent. Setaria showed a linear increase photosynthesis rate with increasing nitrogen percents. Similar relationships were observed between the photosynthesis rate and leaf nitrogen content per unit leaf area. Grasses exhibiting the higher saturated photosynthesis rate in relation of leaf nitrogn percent tended to exhibit the lower increase rate of photosynthesis rate by increase of leaf nitrogen percent at low levels of leaf nitrogen (Figs.2 and 3). Inclination of light-photosynthesis curves were different among the grasses as well as among the nitrogen levels of leaf. Leaves with the higher nitrogen percent exhibited the higher photosynthesis rate and the larger increase of photosynthesis rate with increase of nitrogen content. In leaves with low nitrogen content, light-photosynthesis curves leveled out at relatively low light intensity.

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The effect of density on yield of grain sorghum was studied, investigating variance of each stem. Plots were consisted of 5, 10, 20, 40 and 80 plants/m^2, using varieties of high (Mini Milo 54 BR) and low tillering capacity (NK 129). 1) Generally, the yield increased with increase of density, but the rate of increase of yield were larger in low density than in high density, and the yield of 80 plants/m^2 was lower than that of 40 plants/m^2 in NK 129. Top weight responsed to density roughly as yield did so. 2) The harvest index (HI) of NK 129 decreased with increase of density, remarkably between 20 and 80 plants/m^2. The HI of Mini Milo 54 BR also decreased with increase of density between 20 and 80 plants/m^2, and decreased in the density less than 20 plants/m^2, but HI culculated from main stems did not so. 3) Variance of HI of each main stems was small in low density, and increased in high density, where observed stems of low HI, which had flag leaf of low height, short culm and small shoot weight. In stems, whose flag leaf height and culm length were shorter than structure of leaf distribution, showed low HI, therefor, it is suggested that reducing light intensity may affect the HI of these stems. 4) A part of tillers showed as high HI as main stems, and the others, in spite of having considerably large sizes, showed low HI than main stems. Majority of tillers belongs to small and low HI groups. 5) In this experiment main stems having low HI had a little influence on HI of all in high density.

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Alfalfa plants of two clonal lines (10A, 10B) were grown, after first cutting, in a greenhouse at the controlled temperatures of 15°, 20°, 25° and 30℃ for daytime and under outdoor conditions, respectively, the night temperatures in the greenhouse being 5℃ lower than each day temperature. After 40 days, they were harvested and analysed for nonstructural carbohydrate composition by means of liquid chromatography. Total nonstructural carbohydrate (TNC) contents (% DM) in the plants grown at the controlled temperatures ranged from 4.84 (25℃) to 5.83% (15℃) for 10A and from 5.00 (30℃) to 6.53% (15℃) for 10B, while those in the plants grown outdoors were 7.06% for 10A and 8.27% for 10B. These were generally less than the corresponding values for orchardgrasses grown under the same temperature conditions. Higher TNC contents in the plants grown outdoors were due to higher starch levels. Under the controlled temperatures, glucose levels ranged from 0.24 (25℃) to 0.67% (15℃) for 10A and from 0.42 (30℃) to 0.68% (15℃) for 10B, whereas fructose levels were 0.10 (25℃) 〜0.55% (15℃) for 10A and 0.25 (25℃) 〜0.47% (15℃) for 10B, being generally lower than glucose. In 10A both monosaccharides considerably decreased when the environmental temperature rose from 15℃ to 20℃, whereas in 10B they gradually decreased with the rise in the temperatures. Sucrose levels were 2.45 (25℃) 〜2.98% (20℃) for 10A and 2.44 (outdoor) 〜3.11% (15℃) for 10B. They were higher than the sum of monosaccharides. The effects of the environmental temperatures on sucrose contents were rather little and variable. Starch contents under the controlled temperatures ranged from 1.51 (30℃) to 2.05% (25℃) for 10A and 1.70 (25℃) to 2.27% (15℃) for 10B. The plants grown outdoors contained obviously higher amounts of starch (3.57% for 10A and 4.56% for 10B) than the plants in the greenhouse. Although the effects of temperature on the contents of each sugar were variable, there were clear trends for TNC contents to decrease at higher temperature. As for the ratio of each sugar to TNC, sucrose under the controlled temperatures and starch in outdoor environments accounted for about half of TNC, respectively.

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The distribution of assimilated ^<14>C in the plant parts and photosynthates in orchardgrass was investigated in fall season. Plants were harvested after additional 0, 1, 3, 24, 72, 264 hours following exposure to ^<14>CO_2 for 1 hour. 1) About 30% of the ^<14>C assimilated had been lost from the whole plant during the first 24 hours following exposure. 2) Leaf blades contained above 90% of the total plant ^<14>C after an exposure period of 1 hour, but during the following 24 hours above 50% of the radio activity was exported from leaf blades to other tissues, and consequently after 72 hours root came to a major sink for photosynthate. 3) With time after exposure, ^<14>C assimilated was incorporated into the short-chain fructosan in leaf blades, and long-chain fructosan in leaf sheaths, and long-chain fructosan and structural carbohydrates (insoluble fraction) in root. 4) A little ^<14>C was rapidly incorporated into the long-chain fructosan in both leaf sheaths and roots at short time after exposure to ^<14>CO_2.

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The experiments were undertaken to compare the nutritive value and voluntary intake of fresh materials and 0.5% formic-acid treated silages when harvested in the first, second and third cutting of alfalfa. Digestibility and intake were determined with wethers in digestion trials. 1. In comparison with the fresh materials, dry matter, carbohydrate and residual carbohydrate contents of all silages were low and conversely, ether extract contents and gross energy concentrates of all silages were high. The ether extract of silage showed 9.6 kcal/g. DM, while that of the fresh material was less than that of silage, energy being 6.4 kcal/g. DM. 2. Digestibilities of dry matter and carbohydrate of silages were lower than those of fresh materials, but the digestibilities of ether extract of silages were higher than those of fresh materials. TDN contents of fresh materials were slightly higher than those of silages, while the contents of digestible energy (DE) of fresh materials were slightly lower than those of silages. 3. A reduction in intake was not found with silages. Dry matter intake of these fresh materials and silages averaged were 80g/day/kg. W^<0.75> and these nutritive value indexes ranged from 55 to 78. The amounts of DE consumed/day/kg. W^<0.75> were high from 100 to 200 kcal above the maintenance requirement of wether.

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An experiment was conducted to examine whether the observation of ruminating behavior could be used as an index estimating the herbage intake of grazing ruminants. In the first part of this experiment, three experimental steers (av. 8 months old, 248kg B.W.) were given freshly cut grass from the grazing pasture, and relationship between time spent ruminating and amount of grass ingested was determined. Each steer was given the grass of 30kg (intake when offerd ad lib.), 21kg (70% feeding) or 12kg (40% feeding) in two meals daily during 2-day periods. The time spent ruminating declined as decreasing amount of the grass given, but steers spent longer time in ruminating per kg dry matter ingested when smaller amount of the grass were given. Those were 119, 129 and 166 min/kg D. M. with ad lib., 70% and 40% feeding periods respectively. Thereafter, in the second part of this experiment, the steers were put on pasture and ruminating behavior observed during four consecutive days. The time spent ruminating on pasture became longer in some degree than on ad lib. period in barn feeding. The intakes calculated from ruminating time of grazing steers using the ruminating time per kg dry matter ingested, which was observed on ad lib. period, were 4.8, 5.0 and 5.1kg in dry matter respectively for each of three steers. These values were 98, 97 and 87% respectively, as compared with the intakes determined by ratiotechnique using chromogen and chromic oxide as indicators. From these results, it was suggested that the ruminating time of grazing ruminants could be used as useful index for the herbage intake, and was considered that greater accuracy of the estimates may be made by further examination of some factors affecting ruminating behavior of grazing animals.

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