The effects of IAA (3-indoleacetic acid), TIBA (2, 3, 5-triiodobenzoic acid) and x-ray irradiation on the appearance of abnormal spikelets, especially regarding the changes in sex expression, were investigated with a special variety of paddy rice "Akaho". "Akaho" is known to have very unstable characters in regard to the morphogenic regulation of spikelet genetically and to express various abnormalities of spikelet even under usual cultivating conditions. Since this experiment was carried out in phytotron at 25-30°C, in the winter of 1965-1966, the short-day condition promoted female and depressed male sex expression remarkably as seen in other short-day or day-neutral plants grown under the short day condition. With external application of IAA, the femaleness was promoted further and the maleness was suppressed, decreasing the number of stamens and increasing the organs of intermediate structure that were partially transformed stamens to pistil and the pistils of multi-ovary. On the contrary, the application of TIBA and x-ray irradiation showed clear cut inhibitory effects on the shifting tendency of the control plants toward femaleness, increasing stamens and decreasing the pistils of multi-ovary in number, particularly in the plots of x-ray treatment. In these plots, the morphological abnormalities in glumes and the development of additional glumes became to appear more frequently than in the control, on the other hand. From the results above mentioned, it is clarified that an elevation of auxin level promotes the female and depresses the male sex expression in rice plants. Based upon the results obtained in this study and the writers' other obsevations regarding to the effects of gibberellin on the spikelet morphogenesis, it is considered that the endogenous level of gibberellin-like substances may be high at the early stage of spikelet development and afterwards that of auxin-like substances may become dominant absolutely or relatively, in the regions of organogenesis, and the unbalance of these substances in spikelt development seems to induce various kinds of abnormalities in the spikelet morphogenesis.

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1. Studies on the effects of gibberellin on the spikelet formation were carried out in 1965 and 1966 years, using a special variety of paddy rice "Akaho" which has a genetic character to manifest various abnormalities in spikelets even under the usual cultivating conditions. Gibberellin was applied at the stage just before the panicle differentiation, at the concentration of 100 ppm mixed in the nutrient solution. 2. The symptoms of abnormalities in the control spikelets varied considerably by year and the expression of genetic character on the spikelet formation was seemed to vary according to the environmental factors. 3. Since almost all kinds of the spikelet abnormalities were promoted by the treatment, the physiological conditions caused by the exogenous gibberellin were considered to be quite similar with those induced by the genetic factors concerned with the abnormal formation of spikelets. 4. Though the number of spikelet organs was increased as seen in other varieties, the development of primary branches and spikelets in a panicle was decreased remarkably by the treatment in "Akaho". The latter part of above results was different from what were obtained in the previous experiments on other varieties that every organs in the panicles had been promoted by the exogenous gibberellin. So, the optimum concentration of exogenous gibberellin should vary with the kind of organs or the varietal factors. 5. From the facts that the development of morphologically perfect stamens in a spikelet changes from two to eight in number by spikelet and the percentages of spikelets which have stamens more than or less than six in number increase conspicuously, the exogenous gibberellin is thought to make the physiological conditions very unstable and variable in a panicle by locus. 6. Frequent occurrence of the slightly feminish Intermediate organs and the increment of pistils per a spikelet in number give the impression that the exogenous gibberellin promotes the female tendency in "Akaho", making a rather contrast to that obtained from the previous experiments on other varieties. The above results indicate that the effect of gibberellin on the sex expression may not be specific to the male or female but vary with the internal and external factors. 7. Some considerations were tried on the development of intermediate organs and the appearance of multi-stigmatic pistils and several conflicting phenomena obtained in this and the previous studies were indicated deferring. the decision of the question to the future investigations.

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The study was carried out to compare the effects of gibberellin with those of auxins on the morphogenesis of spikelets in rice plants. Gibberellin, α-indoleacetic acid, β-naphthaleneacetic acid and 2, 4-dichlorophenoxyacetic acid were applied just after the time of young panicle differentiation, in the nutrient solution at various concentrations as seen in table 1. It was reconfirmed that gibberellin had some important effects on the spikelet morphogenesis, as had been reported previously by the writers and not only induced various malformed spikelets but also tended to increase the number of glumes, stamens, stigmata and pistils, causing several kinds of abnormal sexual organs and multi-floral spikelets. On the other hand, as shown in table 2, since such phenemena as found in the plots of gibberellin treatment have not been caused by the application of auxins at all, it is considered that the modes of action of the exogenous gibberellin and auxins on the spikelet morphogenesis are different or contrastic with in many faces especially on the differentiation of lateral organs, among all the staminate one in the spikelet. With regard to sex expression, it is said that auxin level at the differentiating apex determines the sex balance and the concentration promoting maximal stamen growth is lower than promoting maximal pistil growth. In this case of rice plants, exogenous auxin is considered to elevate the auxin level at the spikelet apex up over the maximal concentration, and to suppress the maleness, following no marked promotion in the development of female organ. Recently, gibberellin has been reported by a number of investigators to have promotive effects on the staminate organ, suppressing the pistilate one, but the results obtained in this study are not necessarily agree with them completely, the development of both male and female organs having been promoted by gibberellin application. It was indicated that further extensive studies should be done in order to clarify the real relationship between gibberellin or auxins and sex expression, using various methods of application or concentrations of them, followed by the more critical observations on the effects, not only from the quantitative or morphological but also qualitative or functional standpoints of view, analysing them on differentiation and on growth of primordia.

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雌雄異株植物ヒロハノマンテマは異型化したXY型の性染色体をもつ．ヒロハノマンテマの性染色体は核型の中で最も大きく顕微鏡で観察しやすいため，fluorescent in situ hybiridization (FISH)による性染色体の構造解析が容易である．性染色体は1対の常染色体から進化したとされる．性決定に関わる遺伝子の周囲で徐々に組換えが抑制され非組換え領域が誕生した．一方，偽常染色体領域(PAR)と呼ばれる組換えを起こす領域は減数分裂期に性染色体を対合させ，均等に分配する役割をもつ．私たちは，ヒロハノマンテマの染色体末端の反復配列の詳細な解析により，性染色体のPARの位置を明らかにした．ヒロハノマンテマの興味深い現象として，黒穂菌(Microbotryum violaceum)の感染により雌(♀)にも擬似(♂)が伸長し，両性花のようになることが知られている．この現象を利用し，黒穂菌感染雌株を雄株(♂)のカウンターパートとすることで，Y染色体がもつ(♂)発達促進機能（SPF）の端緒が明らかにできると考えた．私たちは，黒穂菌感染雌(♀)株において，(♂)発達関連遺伝子の発現解析を行った．

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Cyto-histological observations were carried out on the morphogenetically abnormal rice spikelets caused by a low temperature, 14∼18°C. Several cyto-histological abnormalities were found on the stamens, such as, unusually swelled anthers with stigmatic pieces, loculi with tapetal hypertrophy, plasmodium-like matters and abortive pollens etc., as seen in figs. 1∼3. The complex types of various kinds of abnormalities as seen in figs. 2, 3 and 6 were found frequently, suggesting that these abnormalities not were independent each other, but were caused fundamentally by a common physiological background of feminization. On the female organ, various grades of additional ovary formation from carpel-like structures to ovaries as seen in figs. 16∼25, were observed and a good many of the varied multi-pistils and the pistils with multi-ovaries were found in the spikelets consequently. In general, these tendencies of feminization has been said to be brought about by the level-up of the endogenous auxin content. From the fact that the morphological and cyto-histological abnormalities due to the low temperature are quite similar to those induced by the application of gibberellin, it is considered that the gibberellin-like substances may have some strong connection with the spikelet morphogenesis under the low temperature and may act to promote the feminization effects of auxin at the later stage of spikelet formation. About the outgrowth phenomena of the unknown tissues from the ovaries, they were clarified to be resulted from the followings, these were, the unusual development of integuments-particularly the outer one as shown in figs. 8∼11, the disclosure of ovule itself as shown in figs. 12 and 13, and the continuous growth of a part of the fasciated portion of two ovaries as shown in figs. 14 and 15 etc., seemingly due to the so-called "flower vegetativation". Occasionally, the vessel-like cells with partially thickened cell wall as seen in fig. 26 were found at the undeveloped embryo sac mother cell or tetrads and some their neighboring cells. Not only the irregular arrangement of egg cell, synergids, antipodes and polar nuclei in the embryo sac but also abnormal enlargement or degeneration of them, as seen in figs. 27 and 28, were also observed frequently. It was indicated that the sexually intermediate structures changed from stamens appeared most repeatedly on the stamens initiated at the palea side, above all on the right or left one which has developed at the most proximity of the female organ.

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1) This study was carried out to make clear the distribution of morphological abnor- mal spikelts induced by gibberellin. 2) It was indicated that the number of spikelets was increased remarkably with the treatment as previously reported and the increase was more conspicuous in upper primary branches than in lower ones. 3) Main morphological abnormalities, such as inception of additional glumes, chandes of stamens and pistils in number were found more frequently in the upper portion of the primary branches. 4) Judging from the above results, it is considered the morphogenic effects of gibberellin on panicle development are more remarkable in the upper or distal portion of panicles or primary branches. This tendency also supported by the writers' studies on the effects of gibberellin on the vascular development in panicles. 5) On the other hand, so called "white hulls" were found frequently in the basal portion of lower primary branches. So, it is concluded that the initiation of "white hulls" should be brought about by a quite different pathway from that of the morphogenic abnormalities. 6) The difference in frequency of the abnormality in glume, stamen and pistil was indicated and discussed from the stand-point of the ontogenic changes in form and related morphogenic substances in the meristematic tissue of spikelet primordium.

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1. 花梗は小なる維管束の外に稍々大なる4～5個の維管束ありて各々1個の樹脂道を有し,花軸内にあるものと連絡せり。
2. 夢の各裂片と花瓣は略々中央部に稍々大なる維管束ありて篩管部内に稍々大なる樹脂道あり。基部に大にして先端になるに從ひて小となる。側方に分岐せる維管束内にも樹脂道の小なる枝を分岐す。猶花瓣は中央のものと關係なくその左右兩側に1～2個の樹脂道を有するものあり。これも同じく維管束に伴ふ。夢・花冠の樹脂道は花梗内のものと連絡す。
3. 雌花にあるは何れも短小にして萎縮せる葯を有し,中に花粉を有せす。雄花にあるものは長大にして縦に裂目を有する葯ありて,中に花粉を有す。花絲・葯何れも樹脂道を有せず。
4. 雄花にある雌蕊は短小。胚珠及び子房壁に樹脂道を有せず。雌花に於ては胚珠内には樹脂道を有せざるも子房壁には蕾の時よの樹脂道が存在し維管束に伴ふ。初めは1列輪状に配列するも子房の發達と共にその數を増し,不規則に配列す。稍々發育せるものは花柱内にも多くの樹脂道をみるも,柱頭内になこれを有せす。
5. 雄花の花盤は幅廣く,中央部稍々凹む。縦斷面に於て盃状をなす。雌花にありては花盤は幅狭く,縦斷面に於て楕圓形をなす。樹脂道は花盤近くまで達するも花盤内には有せず。

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Vatious morphogenic abnormalities as shown in figures were observed in the rice spikelets which were grown under low temperature-day temperature 14-18°C and night temperature 14°C. Morphogenic abnormalities found in the spikelets may be summarized as followings: 1) changes of organs in number, especially increment in number, 2) remarkable phenomena of fusion of inter and/or intra organs of lodicules, stamens and ovaries, 3) appearance of organs of intermediate and bisexual structures, 4) changes in sex expression, promoting femaleness and depressing maleness, 5) continuance of vegetative growth in the spikelets with no formation of sexual organ, incepting only glume and branch primordia, 6) exposure of extraordinarily developed ovule or integument from ovary through the style canal, 7) frequent occurence of abnormally swelled tissue or organ, and 8) appearance of multi-floret spikelets, etc. From the results above mentioned it is considered that the morphogenic regulation in the meristematic tissue of spikelet primordia may become unstable and the disturbance of organ development tends to be occured, by the low temperature treatment. Some discussions were tried on the relationship between the appearance of morphogenic abnormalities due to a low temperature treatment and the level of some growth substances, auxins and gibberellin, in spikelet primordium, based upon the writers' experimental results previously reported.

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千葉県において，ナシ「幸水」の心腐れ症は生産現場で認識しにくく，消費者の産地に対する信用に関わるため，問題となっている。本症状は，薬剤だけでは完全な防除は難しいことから，耕種的防除も併せた対策が必要である。そこで，薬剤散布に加え，感染経路の一つと考えられる花かすの人為的な除去試験を行い，その効果を検討した。併せて，花かすからの胴枯病菌の分離調査を行った。その結果，花かすを除去した区における発症果率は2010年および2011年の試験で低下した。一方，2012年の除去効果は判然としなかった。また，この年は花かす組織から胴枯病菌が分離される頻度は低かった。

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マツモ（Ceratophyllum demersum）は沈水性の水生植物であり，花被片に取り囲まれた多数の

からなる特異な形態の雄花を持つ．この雄花における花器官の配列（数性）は多様であり，1つの個体内にもらせん状，3数性，4数性そして不定形という様々な数性が混在する．この雄花の花の発生過程を詳細に観察した結果，発生初期ではは背軸側から向軸側への単一方向発生を示すが，発生後期の花の内部のは必ずらせん状に発生することが分かった．この初期の単一方向発生は，上の節の葉との接触による物理的圧力によって発生が変化したものであり，マツモの雄花の本来の発生パターンはらせん状であると考えられる．このことは，花発生の点からはマツモは基部被子植物群と共通性があるということを示している．また，マツモの雄花で様々な数性が生じることは，物理的接触による発生パターンの変化に起因するものであり，被子植物における数性の多様性も花芽に対する物理的な圧力の違いが原因の1つとなって引き起こされている可能性がある．このモデルを実験的に検証するため，シロイヌナズナ（Arabidopsis thaliana）の若い花芽に人工的に物理的圧力を与え，それによる花発生の変化を解析する新たな実験系を開発した．現在この実験系を用いて，物理的圧力が花の数性に及ぼす影響を明らかにすることに取り組んでいる．

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The study was performed to investigate the effects of X-ray irradiation or/and gibberellin on the spikelet morphogenesis in rice plants. X-ray irradiation was carried out at the differetiating stage of spikelet at the dosages of 1kr, 5kr, 10kr and 20kr, and gibberellin was applied in the nutrient solution at the concentration of 100 ppm on the day after the X-ray treatment. Various abnormalities, these are, appearance of malformed spikelets, development of additional glumes, variation in stamen initiation, increase of stigmata in number, development of multiple pistils in a spikelet etc., have been induced by X-ray irradiation. These phenomena are closely similar to those induced by gibberellin in many faces. When gibberellin application was added to X-ray treatment, it was found that the morphogenetic effects of gibberellin had been promoted strongly by the pre-treatment of X-ray and every abnormality caused by gibberellin had been strengthened remarkably. Based on the results above mentioned, it is considered that the physiological changes as influenced by X-ray may not be inhibitory to exhibition of gibberellin activity but strongly promotive ones. A few considerations were tried on the relationship between gebberellin and auxin, regarding to the spikelet morphogenesis from the standpoint of auxin economy, since a level down of auxin had been reported by a number of investigators to be caused by X-ray irradiation.

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本研究では，弁化型八重咲きシクラメンにおいて，花の器官数と形態の季節的な変化，ならびに生育温度が花器形態に及ぼす影響を調査した．季節変化する温度条件下で生育した植物体では，花の器官数と形態は時間経過とともに変化したが，変化の程度は系統によって異なっていた．つまり開花期間を通して，弁化数が“変動”もしくは“比較的安定”な二つのタイプが存在した．異なる一定温度条件下で生育した植物体では，whorl 3 において完全に弁化したの割合は 15°C が最も高く，その後は 25°C，20°C と続いた．完全に弁化したの割合とは対照的に，whorl 3 において不完全に弁化したの割合は 20°C が最も高く，その後は 25°C，15°C と続いた．whorl 3 における状器官の割合は処理温度間で有意な差は認められず，完全に復帰したの割合は 25°C のみ抑制されていた．状器官の総数は 15°C と 20°C で同程度であったが，二つの温度間ではそれらが発達した位置が有意に異なっていた．15°C では由来花弁の内側に形成されたのに対して，20°C ではの復帰が誘導された．結論として，花器形態は季節的変化を示し，生育温度は弁化型八重咲きシクラメンの弁化に影響を及ぼすといえる．しかしながら，弁化に及ぼす影響は遺伝子型によって異なる．

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Auxiliary bud at 1∼3 node : These buds did not develop to reach the stage of flower bud differentiation. Auxiliary bud at 4∼15 mode : Stage of flower bud differentiation, Des 10; stage of sepal differentiation, Jan.20. Auxiliary bud at 16∼19 node : Stage of flower bud differentiation, Nov.20; stage of sepal and stamen differentiation, Jan.20. Auxiliary bud at 20∼24 node : Stage of flower bud differentiation, Nov.20; stage where floral parts increase in size, Mar.30. Auxiliary bud at 25∼30 node : Stage of flower bud differentiation, Nov.20; stage where floral parts increase in size, Mar.30. Auxiliary bud at 31∼32 node : Stage of carpel differentiation, Jan.20; stage where floral parts increase in size, Mar.30. Auxiliary bud at 33∼36 node : Stage of sepal and stamen differentiation, Jan.20; stage where floral parts increase in size, Mar.30. Auxiliary bud at 37∼38 node : Stage of sepal differentiation, Jan.20; stage where floral parts increase in size, Mar.30. Auxiliary bud at 39∼40 node : Stage of flower bud differentiation, Jan.20; stage where floral parts increase in size, Mar.30.

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理論と実験生物学の長年の挑戦にもかかわらず,生殖戦略として性がこんなにも一般的なのはなぜかという問はまだ十分説明されていない.本稿では,その回答の一部として,1)真正粘菌(Physarum polycephalum)のミトコンドリア線状プラスミド(mF),2)ヒラアオノリ(Ulva compressa)の配偶子の性的非対称性,3)黒穂菌(Microbotryum violaceum)によるヒロハノマンテマ(Silene latifolia)の雌雄性の撹乱について紹介する.ミトコンドリアは母性遺伝する.mFプラスミドは両親由来のミトコンドリアを融合することで,ミトコンドリアの母性遺伝に抗して父親由来のミトコンドリアから母親由来のミトコンドリアへ伝播することができる.これはバクテリアの接合プラスミドFを髣髴させる.mFやFのような利己的な分子共生体が引き起こした接合が最初の性だったのではないかと考えられている.接合や性的組換えは選択圧に対して優位にはたらく.この利己的DNAの分子共生体説は,性の起源に直接関与するだけでなく,性の進化の次の段階を理解するのにも重要な意味をもつだろう.本稿では,こうした性の起源と進化に関する新しいアイデアとして,ヒラアオノリの雌雄配偶子の眼点に対する接合装置の性的非対称性と,ヒロハノマンテマの性を撹乱する利己的共生菌M.violaceumについても,性と遺伝的アーキティクチャを交錯するものとして紹介したい.

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