Studies on the generative nuclear division. II. Behavior of the chromosomes during the generative nuclear division in Allium fistulosum.

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Abstract
The behavior of the generative nuclear chromosomes in the cultured pollen tube in A. fistulosum was studied. The mitotic phases from mid-prophase to late-prophase and that from metaphase to telophase were observed in 2- and the 4-h cultures, respectively. C-banding showed that the constitutive nuclear topograph remained invariable through telophase of the primary microspore division in a pollen grain to prophase of the secondary generative nuclear division in a pollen tube. Free spindle-formed germ cell in the pollen tube cytoplasm changed into an oval-like form before going into the secondary generative nuclear division. The formed mitotic germ cell could have a whole round directional mitotic axis in the pollen tube. Usually the mitotic axis has a right angle orientation against the pollen tube membrane. But when the spindle body prepares to extend, the mitotic axis may rotate to get the most stable orientation in the pollen tube. The vegetative nucleus (= the pollen tube nucleus) usually moves near the germ cell, but sometimes, it changes its form into a filamentous, extremely extended form.