GLOEOSPORIUM KAWAKAMII, MIYABE に關する研究 : III 分生胞子の發芽に關する知見
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The conidia of Gloeosporium Kawakamii germinate vigorously when they are kept at 20° to 30°C. Below 20°C germination occurs very slowly, and above 30°C similar inhibiting action is also observed. The germ tubes grow most rapidly between 25° and 31°C, especially about 28° to 30°C. From this observation, it seems that the optimum temperature for the growth of this fungus is about 28° to 30°C. The conidia are able to germinate in culture media with rather wide range of hydrogen ion concentration. More than 98 per cent of the conidia germinate, when hydrogen ion concentration of the solutions lies between PH 4.6 and PH 8.8. When PH value falls to 4.1 or to 3.8 germination is strongly retarded, and at PH 3.6 no germination is observed. In alkaline ranges, the conidia are retarded to germinate when PH value of the media is about 9.0 to 9.2, although 63 per cent of them are obsorved to germinate at PH 9.2. The optimum PH value for the growth of the germ tubes is about PH 6.0, which shows that the slight acid reaction may favour to the growth of this fungus. In acid ranges, the growth of the germ tubes decrease rapidly with the fall of the PH value of the media. In alkaline solutions, the growth of the germ tubes suddenly decrease at PH 8.8. Occasionally in hanging drop cultures, the conidia of the fungus germinate with difficulty. However when the same conidial suspensions are applied en glass plates, the conidia germinate easily. This phenomenon, the inhibition of spore germination, is believed also to be due to the density of the spore suspensions, When a high density of the spore suspension, 3500 per 1 sq. mm., is used, only 15 to 25 per cent of spores germinate, eveti when the suspension drops will be placed on glass plates. On the contrary, when the suspension is measured to contain less than 60 spores per i sq. mm., a very low density of spores, 100 per cent of them germinate. This phenomenon is found not to be due to any oxygen supply or any nutritional relations. When the spores of this fungus are washed thoroughly with distilled water and centrifuged for four times, and then the spore density of the suspension is not so highly furnished, the spores germinate relatively good even though they may be kept in the suspending conditions. For the interpretation of these facts the author is of opinion that the inhibited phenomenon of the spore germination is due to the etabolic product of conidia, which is restrained to diffuse by the colloidal substance around them, and also is restrained to diffuse off when conidial suspension is furnished in high density. The author measured the spores per 1 sq. mm. to show the density of a spore suspension. To show the density of the spore suspension of the fungus, of which conidia are heavier than water and soon sink to the bottom when they be set still, it is found to be a proper method to count the number per unit area rather than per unit volume. The germ tubes of the conidia produce brown coloured appressoria, when they came in contact with a solid matter. Oxygen supply, light or nutrient telations seems to have little influences upon the formation of appressoria.本菌の分生胞子は20°-30℃に於て最も旺盛に發芽し, 20℃以下又は30℃以上に於ては急激に發芽歩合を減ずるものにして, 34℃に於ては殆んど發芽せず。而して發芽管の伸長度は25°-31℃就中28°-30℃に於て最も旺盛にして, 本菌の生長に對する最適温度はこの附近にありと云ふを得べし。本菌の分生胞子は培養液の酸域アルカリ域に亘れる可なりの廣範圍に於てよく發芽するものにして, PH4.6-PH8.8 の間に於ては98%以上の發芽歩合を示せり。發芽管の伸長度を見るに PH6.0 附近に於ては最大を示し, 之より酸度の上昇するに伴ひて急にその伸長度を減ずるも, アルカリ度の上昇に對してはその影響比較的緩慢なるが如く伸長度は徐々に減退せり。本菌の分生胞子は, 之を懸滴培養となす場合には時として發芽せざることあり。然るに同一液を硝子面の上に置く時は常によく發芽するものなり。又菌液の胞子密度高き時は水滴を上面に置くも發芽歩合不良にして, 胞子密度低き時は之に反す。然るに本菌の胞子を豫め蒸溜水を以て十分に洗滌せる場合には多少その發芽歩合は佳良となる。但し胞子密度極めて高き場合にありては依然その發芽歩合不良なり。かくの如き現象は酸素の供給又は養分の關係によるものに非ざることを證明し得たり。著者はかくの如き現象の説明として次の如き假説を設けたり。本菌胞子の外圍に存せる膠状體は胞子の發芽に際し起る所の代謝機能の發動を阻止するが如く働き, 胞子は發芽時に於ける代謝産物の十分洗除せらるゝに非ざれば發芽するに至らざるものとす。かくの如き假説によつて前記の諸現象を説明すれば, 懸滴培養に於ては膠状體は胞子の外圍に吸着して多量に殘存せるが爲に胞子の發芽は不良なるも, 水滴を基物の上面に置くときは胞子は下底に沈着するを以て, 胞子外圍の膠状體は下底に沿ひて擴散し, その結果胞子の周圍に於ては著るしくその量を減ずるに至り, 爲に胞子は發芽するに至るものとす。胞子を洗滌せるものに於ては, その外圍に存せしかくの如き膠状體の著るしく減ぜるが爲に, 胞子は浮游状態に於ても比較的よく發芽すると雖も, 菌液の胞子密度大に過ぐる時は, 發芽時に於ける代謝産物の十分に排除せられざるが爲に發芽不良に陷るものとす。而して無處理の胞子を以て胞子密度の高き菌液を作れる場合に於てはかくの如き因子が二重に働きてその發芽を阻止するに至るものとす。著者は本菌々液の胞子密度を表はすに當り1平方粍常りの胞子數を以てせり。一般にGloeosporium 屬の菌の分生胞子は水よりも重くして浮游液に於ては容易に下底に沈着するものなるが故に, その菌液を靜置せる場合に於ては, 菌液一定量中に於ける胞子數を計測するよりも, むしろ一定面積内に沈着せる胞子數を以てその密度を表はすを一層適切なるものとす。本菌の分生胞子の發芽管は固體に接觸する時は附着器を生ずるものにして, 之が形成については酸素の供給, 養分關係等は影響するところ甚だ少なきものゝ如し。
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