Among the reforested trees. Pinus densiflora SIEB. et ZUCC. and P. thunbergii PARL. are the important ones in Japan. Many taxonomic studies have been made on the hybrids between both species, which are called "Akakuromatsu" Pinus densi-thunbergii UYEKI. Hitherto, it has been illustrated that the efflcient taxonomic Indicators were some anatomical characteristics In the needles, for examle, the position of resin canal and the amount of hypodermal cells. However, these classifications were carried. out on the natural hybrids, so they had been used without recognizing the genetical systems of the indicators. Therefore, If some specific genetical systems such as dominant or maternal. effect exist in the indicators, the classification may be inadequate and erroneous. Moreover, if the number of the indicators are a few, the classification will be often devoid of objectiveness. The present study was schemed to examine these problems.

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In order to isolate growth and germination inhibitors from the hulls of dormant rice seeds, the seeds of a Japonica cultivar 'Koshihikari' and an Indica one 'Surjamukhi', which have strong dormancy, were used. The rice hull (ca 200kg) was soaked in 80% methanol for about 2 months. The methanol extracts were concentrated to an aqueous phase by the flash evaporator at below 40°C. The aqueous phase was extracted with chloroform and the active fraction was moved in chloroform. The active chloroform fraction was successively fractionated by organic solvents : n-hexane, benzene, ether, ethylene chloride, and ethyl acetate. The biological activity of each extract was checked by lettuce germination test. The active fraction checked was further separated according to solubility in dilute acid or base. The neutral fraction of benzene and ether extracts showed a strong inhibitory activity. The active fraction was used for further chromatographic study. By the silica gel thin layer chromatography with a developing solvent, benzene : ethyl acetate (10 : 1), two active compounds were crystallized and were identified as momilactone-A (C20H2603) and -B (C20H26O4) The momilactones inhibited the seed germination and the seedling growth of rice and lettuce at a concentration of 10-3M. Especially, these substances remarkably inhibited the root growth of rice seedling at 10-5-10-3M. Momilactone-B had stronger inhibition than momilactone-A. The inhibitory activity of momilactone-B was similar to that of a typical growth regulator, abscisic acid. 'Koshihikari' contained more momilactone-A than momilactone-B, while 'Surjamukhi, which has stronger dormancy than 'Koshihikari', held more mornilactone-B than momi-lactone-A. It was supposed that the content of momilactone-A and -B in rice seeds might vary with the rice cultivar. The inhibitory activity of momilactones was partially reduced by GA3 or IAA. In considering the breaking of dormacy in rice seeds, it may be neces-sary to check the interaction between momilactones and GA or IAA which has an important role during rice seed germination.

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It has been shown in the previous studies that ethylene imine (EI) sensitivity of rice seed changed exceedingly when they were treated after various pre-soaking tlmes. In the present paper, the factors involving in this marked change of EI sensitivity were investigated to clarify the biological activity, especlaly mutagenlc activity of EI. The unhulled seeds of a rice variety Akibare were treated for 2 hours with EI of 0.3 percent (v./v.) after various pre-soaking times. Sensitivity of pre-soaked seeds was evaluated on the criteria of growth retardation in seedling helght. Chlorophyll and morphological mutants were scored at the seedling stage in the next generation (M₂). The times of first cell division and DNA synthesis in the area of shoot apex of the non-treated seed were determined using Feulgen staining and micro-photometrlc methods.

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Rice seeds were germinated and grown in culture medium with 2μCi/ml ³H-BU. After various periods of culture, nucleic acid was extracted by modified STS method and ³H-BU incorporation was measured. A steady increase in this incorporation into RNA and DNA was found. However, ³H-BU integration in DNA of stem meristem was very low, resulting in about I per cent of incorporated ³H-BU. Levels of RNA and RNA in ³H-BU-grown seedlings followed the same pattern as the controls. Additional aminopterin, on the other hand, induced reduction in ³H-BU incorporation into DNA and severe inhibition of root elongation. When seeds were treated with AP and BU, either alone or along with aminopterin, seedling growth was reduced by approximately 20 per cent in AP and by 40 per cent in BU. In the M₂ generation, different types of mutants were segregated at the frequency of 10^-^3-10^-^2. Partrcularly of chlorophyll mutants about 60 per cent was "strrata" with albino-sectorial stripe. Finally, it was concluded that in rice AP and BU could induce mutations, using the procedure of comparatively short culture of seeds in the medium with these analogues.

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To analyze the growth of embryo of Oryza sativa cultivar, , "Nihonbare" in detail, caryopses were collected at every ninety minutes. At c.ach time, (relative) growth rate was calculated for the length and the thickness of embryo, and the time series analysis was applied to the variations of the growth rate. At first, correlogram analysis was made on the stationary growth rate and the apparent periodicity was detected as a result of the calculation. In the next place, as a pcriodogram, the correlation coefficient between the autocorrelogram and the cosine function was employed. Periodogram shows two sharp peaks and reveals the existence of two rhythms in the variations of the growth rate. In other words, the variations of the growth rate are represented by the summation of two cosine functions. Periods of two cosine functions are 5. 16 and 5.69 hrs for the growth rate in length and 5.13 and 5.67hrs in thickness. The difference of periods between the growth rate in length and in thickness is not significant. In the next place, to reveal the biological nature of two rhythms of the growth rate at the cellular level, the increasing rate in cell number on the central longitudinal section of embryo was calculated. On the carefull comparison, it was confirmed that the two rhythms of growth rate agreed very well with the variations of the increasing rate in cell nurnber except at the early stage of the development. At the early stage, both the growth rate ancl the increasing rate in cell number seem to show arhythmicity. Therefore, it is considered that the two rhythms of growth rate reflect the rhythinicity of cell divisions. However, tho two rhythms do not exist at the beginning, and appear in the early period of the development. The existence of the two rhythms indicates that the cells divide synchronously in two regions. The authol- supposes that the two rhythms correspond to the synchronous cell divisions at the two growing points in plumule and radicle.

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The relationship between stomatal frequency and photosynthesls in barley was studied to determine whether stomatal Lrequency can be used to screen plants for high photosynthetic ca pacity. Photosynthesis and transpiration of 7 cultivars differing in stomatal frequency were measured (Table 1). The analysis of variance (Table 2) revealed that these cultivars differed significantly in stomatal frequency and photosynthesis but not in transpiration. There was a positive correlation between stomatal frequency and photosynthesis, r=0.94 and also between stomatal frequency and transpiration, r=0.86 (Fig. 1). The coefficient of regression of photosynthesis on stomatal frequency was 0.207, which indicated that the increase of one stoma per mm² resulted in the increase of 0.207 CO₂ mg/dm²/hr intake. By Gaastra's equation, the resistance of the air (r_a), the stomata (r_s), and the mesophyll (r_m) to the diffusion of CO₂ and the resistance of the air (r_a'), and the stomata (r_s') to the diffusion of H₂O were computed (Table 3). Stomatal resistance tended to decrease as stomatal frequency increased (Fig.2). Mean (r_s')/mean (r_a'+r_s)=0.60 and mean (r_s)/ mean (r_a+r_s+r_m)=0.16. It appears that transpiration was more affected by the change of rs' than photosynthesis. But the correlation between stomatal frequency and mesophyll resistance was -0.93. This indicates that mesophll resistance was affected by changes in stomatal frequency whose effect was not wholly separated by Gaastra's equation.

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Disease dispersion from a point source in pure and mixed stands of susceptible and resistant plants was followed by a simulation made by using the equation in respect with disease dispersion, y=are-5P. The effect of mixing of resistant plants in susceptible plants to inhibit the disease increase is reduced with the increase of disease dispersal gradient, 6, Iarger than 0.5. Infection rates calculated by the number of new lesions decrease straightly with the decrease of the proportion of susceptible plants against the logarithm of the proportion. This decrease is inhibited by the increase of disease dispersal gradient, 6. The effect of mixing of resistant plants is decreased with the decrease of spacing density. The infection rates calculated by the total number of new and old lesions give a dropping curve which is asymptotic to 0.

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Ufeit-type electrophoretic apparatus for polyacrylamide gel-columns (U-type) was devised and the procedure of isoelectric focusing was described. The procedure for peroxidase zymograrns of rice plant was noted under thirty-six conditions different in voltage, running time and concentration of electrode solutions. The condition that developed the best zymograms over the whole length of gel-column was taken as the optimum condition as follows: gel-column 3mmx150mm long, 10V/cm for voltage, 16-18hrs. for running time and 0. 8% V/V(P)∼2. 2% V/V(T) or 1. 2% V/V(P)∼3.3% V/V(T) for electrode solutions.Ufeit-type electrophoretic apparatus for polyacrylamide gel-columns (U-type) was devised and the procedure of isoelectric focusing was described. The procedure for peroxidase zymograrns of rice plant was noted under thirty-six conditions different in voltage, running time and concentration of electrode solutions. The condition that developed the best zymograms over the whole length of gel-column was taken as the optimum condition as follows: gel-column 3mmx150mm long, 10V/cm for voltage, 16-18hrs. for running time and 0. 8% V/V(P)∼2. 2% V/V(T) or 1. 2% V/V(P)∼3.3% V/V(T) for electrode solutions.

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[in Japanese]

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