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Pollen germination has three stages; hydration, activation and pollen tube emergence. The pollen grain is severely dehydrated so that its mass is reduced enabling it to be more easily transported from flower to flower. Germination only takes place after rehydration, ensuring that premature germination does not take place in the anther. Hydration allows the plasma membrane of the pollen grain to reform into its normal bilayer organization providing an effective osmotic membrane. Activation involves the development of actin filaments throughout the cytoplasm of the cell, which eventually become concentrated at the point from which the pollen tube will emerge. Hydration and activation continue as the pollen tube begins to grow. In conifers, the reproductive structures are borne on cones. The cones are either pollen cones (male) or ovulate cones (female), but some species are monoecious and others dioecious. A pollen cone contains hundreds of microsporangia carried on (or borne on) reproductive structures called sporophylls. Spore mother cells in the microsporangia divide by meiosis to form haploid microspores that develop further by two mitotic divisions into immature male gametophytes (pollen grains). The four resulting cells consist of a large tube cell that forms the pollen tube, a generative cell that will produce two sperm by mitosis, and two prothallial cells that degenerate. These cells comprise a very reduced microgametophyte, that is contained within the resistant wall of the pollen grain. The pollen grains are dispersed by the wind to the female, ovulate cone that is made up of many overlapping scales (sporophylls, and thus megasporophylls), each protecting two ovules, each of which consists of a megasporangium (the nucellus) wrapped in two layers of tissue, the integument and the cupule, that were derived from highly modified branches of ancestral gymnosperms. When a pollen grain lands close enough to the tip of an ovule, it is drawn in through the micropyle ( a pore in the integuments covering the tip of the ovule) often by means of a drop of liquid known as a pollination drop. The pollen enters a pollen chamber close to the nucellus, and there it may wait for a year before it germinates and forms a pollen tube that grows through the wall of the megasporangium (=nucellus) where fertilisation takes place. During this time, the megaspore mother cell divides by meiosis to form four haploid cells, three of which degenerate. The surviving one develops as a megaspore and divides repeatedly to form an immature female gametophyte (egg sac). Two or three archegonia containing an egg then develop inside the gametophyte. Meanwhile, in the spring of the second year two sperm cells are produced by mitosis of the body cell of the male gametophyte. The pollen tube elongates and pierces and grows through the megasporangium wall and delivers the sperm cells to the female gametophyte inside. Fertilisation takes place when the nucleus of one of the sperm cells enters the egg cell in the megagametophyte’s archegonium. In flowering plants, the anthers of the flower produce microspores by meiosis. These undergo mitosis to form male gametophytes, each of which contains two haploid cells. Meanwhile, the ovules produce megaspores by meiosis, further division of these form the female gametophytes, which are very strongly reduced, each consisting only of a few cells, one of which is the egg. When a pollen grain adheres to the stigma of a carpel it germinates, developing a pollen tube that grows through the tissues of the style, entering the ovule through the micropyle. When the tube reaches the egg sac, two sperm cells pass through it into the female gametophyte and fertilisation takes place.

INTO JAPANESE

花粉の発芽には 3 段階あります。水分補給、活性化および花粉管の出現。花粉の穀物は、花から花への運ぶより簡単にすることが可能その質量が減少、脱水症状がひどいです。発芽は、水分補給の早期発芽しません、葯の場所にならないことを確認後に起こる。水和アル

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On the germination of pollen in 3 stages. The emergence of rehydration and activation of pollen tubes. Pollen grains can carry from flower to flower more quickly to reduce its mass, dehydration is terrible. Germination takes place after make sure do not germinate early hydration and become a place of,

INTO JAPANESE

3 段階で花粉の発芽。水分補給と花粉管の活性化の出現。花粉は花から花へをより迅速にその質量を減らすために運ぶことができる、脱水がひどい。発芽後行われない作る確か初期水和を発芽していないの場所になります。

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3 stages in the germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Pollen from flower to flower you can carry to more quickly reduce its mass, dehydration is terrible. No germination after making becomes the place not certainly germinate early hydration.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。花粉より迅速にその質量を減らすために運ぶことができる花から花へ、脱水がひどい。なる場所後も発芽はたしかに初期水和を発芽します。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. From the flowers that can carry pollen more quickly reduce its mass to a blossoms, dehydration is terrible. The location after germination is the sprouting early hydration certainly.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。脱水がひどいより迅速に花粉を運ぶことができる花から、花にその質量を削減します。発芽後の場所は確かに発芽の初期水和です。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. From the flowers that can carry the pollen from severe dehydration quickly reduces its mass flowers. Place after the germination is certainly early hydration of germination.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。運ぶことができる花から重度の脱水から花粉はすぐにその大量の花を減少します。場所は、発芽は発芽の確かに初期水和後。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. From flowers that can carry from severe dehydration pollen reduced the abundance of flowers immediately. Where is germination germination certainly after initial hydration.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重度の脱水症から運ぶことができる花から花粉が花の豊富さをすぐに減少します。ここは確かに初期水和後発芽発芽です。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Flowers can carry severe dehydration from pollen reduces the abundance of flowers immediately. This is certainly early hydration late bud germination.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。花を運ぶことができる花粉から重度の脱水すぐに花の豊富さを軽減。これは確かに初期水和後半芽発芽です。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. From pollen that can carry flowers severe dehydration quickly reduce the abundance of flowers. It is certainly early hydration in the late bud germination.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。花を運ぶことができる花粉から重度の脱水症はすばやく大量の花を軽減します。確かに初期水和後半芽発芽です。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Severe dehydration reduces flowers quickly and large amounts of pollen that can carry flowers. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重度の脱水症はすぐに花を削減花を運ぶことができる花粉の量が多い。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Heavy pollen can now carry flowers cut flowers is severe dehydration. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重い花粉が運ぶ花切り花今は重度の脱水症です。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. It is a flower vase now carry heavy pollen is severe dehydration. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。花の花瓶今運ぶの重い花粉が重度の脱水です。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. This is a vase of flowers now carry heavy pollen is severe dehydration. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。これは花の花瓶を運ぶ重い花粉が厳しい今脱水。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. This vase of flowers to carry heavy pollen is severe dehydration right now. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重い花粉を運ぶために花のこの花瓶は重度の脱水症を今すぐです。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Heavy pollen to carry this vase of flowers is severe dehydration is now. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重い花粉を花のこの花瓶を運ぶには厳しい脱水は、ようになりました。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. This vase of flowers to carry heavy pollen severe dehydration is now shown. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重度の脱水症は今示されている重い花粉を運ぶために花のこの花瓶。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. To carry heavy pollen now shown severe dehydration in this vase of flowers. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。今この花瓶の花に重度の脱水を示す重い花粉を運ぶ。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. Heavy pollen now flowers in this vase shown severe dehydration to carry. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。重い花粉を運ぶため重度の脱水を示すこの花瓶の花を今。初期水和後半芽発芽は確かに。

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3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. It's now carry heavy pollen indicates severe dehydration, this vase of flowers. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。それは今運ぶの重い花粉では、重度の脱水、この花瓶の花のことを示します。初期水和後半芽発芽は確かに。

BACK INTO ENGLISH

3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. It indicates that severe dehydration, this vase of flowers in the heavy pollen now carry. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。それは重度の脱水症、重い花粉の花のこの花瓶今運ぶことを示します。初期水和後半芽発芽は確かに。

BACK INTO ENGLISH

3 stages of germination of the pollen. The emergence of the activation of the hydration and pollen tubes. It is now carrying this severe dehydration, heavy pollen flower vase. Early hydration late bud germination is indeed.

INTO JAPANESE

花粉の発芽の 3 段階。水分補給と花粉管の活性化の出現。今、この重度の脱水症、重い花粉花の花瓶を運んでいます。初期水和後半芽発芽は確かに。