The critical period of degeneration of tapetum and pollen grains in Satsuma orange (<i>Citrus unshiu</i> MARC.)

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  • 温州ミカンの花粉退化および葯のタペート細胞崩壊の時期について
  • 温州ミカンの花粉退化および葯のタペート細胞崩壊の時期について〔英文〕
  • ウンシュウ ミカン ノ カフン タイカ オヨビ ヤク ノ タペート サイボウ ホウカイ ノ ジキ ニ ツイテ エイブン
  • The critical period of degeneration of tapetum and pollen grains in Satsuma orange (Citrus unshiu MARC.)

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In order to study the mechanism of male-sterility in Satsuma orange, the critical period of the degeneration of pollen grains and anther tapetum was determined. The results obtained were summarized as follows:<br>1. The microspores at the vacuole stage were variable in size, and their sizes at the stages of vacuole appearance and vacuole disappearance were about 20.88 and 27.08μ, respectively.<br>2. The great majority of sterile pollen grains investigated at the stage of pollen maturity could be included in the medium-sized group (from 22.5 to 27.5μ in diameter).<br>3. The degeneration of pollen grains might take place at the vacuole enlarging stage, thereafter, they showed little or no increase in their own size and became empty medium-sized pollen grains.<br>4. During the stage of vacuole disappearance, a few microspores with starch granules and a large number of microspores without starch granules were observed. The latter became sterile throughout thecourse of pollen grain development.<br>5. The tapetum remained cellular and the tapetal cells became to be polynucleated at the pollen-tetrads stage. Breakdown and disappearance of the tapetum occurred at the vacuole enlarging stage and after the pollen mitosis stage, respectively.<br>6. It may be concluded that the critical period of the degeneration of tapetal cells and pollen grains of Satsuma orange is the vacuole enlarging stage of microspores.

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