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Qin Chen and Hai Y. Li

An improved method is described for the isolation of potato metaphase chromosomes for karyotypic and cytogenetic studies. Root tips from diploid Mexican species, Solanum pinnatisectum (2n = 2x = 24) and tetraploid cultivated S. tuberosum (2n = 4x = 48) were given four different pretreatments. The synthetic pyrethroid, Ambush, was the most stable and effective pretreatment reagent, providing the highest percentage of mitotic chromosomes at metaphase and the best spread of countable chromosomes for cytogenetic studies. Compared with an Ambush pretreatment at concentrations of 100-400 ppm, 1 to 10 ppm Ambush produced more easily distinguished chromosomes, which can be useful for comprehensive observation and karyotype analysis in both 2x and 4x potato species. This improved technique for examining mitotic chromosomes will be helpful in describing karyotypes, characterization of new hybrids, and identifying chromosome structural changes that are important in breeding schemes.

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Hailin Shen, Zhendong Liu, Ke Yan, Liren Zou, Jinghui Wen, Yinshan Guo, Kun Li, and Xiuwu Guo

. Observation of the ovule morphology and functional megaspore mitosis. The morphological differences in the ovule of treated and control flowers were observed at each development stage. On day 3 after treatment, an anatropous ovule consisting of a near round

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Dongmei Wei, Huimin Xu, and Ruili Li

μm. Bicellular pollen stage. After microspore mitosis, the bicellular pollen grain contains a small generative cell and a large vegetative cell. The large vacuole in the vegetative cell began to decompose at this stage, and several small vacuoles

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Srini C. Perera and Peggy Ozias-Akins

Petiole protoplasts of the sweetpotato [Ipomoea batatas (L.) Lam.] cultivars Red Jewel and Georgia Jet formed cell walls within 24 hours and divided in 2 to 3 days. Pretreating enzyme solutions with activated charcoal increased the viability and division frequency of protoplasts. Culture of protoplast-donor plants in a medium containing STS did not affect plant growth, protoplasm yield, or viability, but did increase the division frequency. Culture of protoplasts for 24 hours in a medium containing DB, a cell wall synthesis inhibitor, or staining of protoplasts with FDA did not significantly affect division frequency. The division frequency of protoplasts cultured in liquid medium was significantly higher than that of protoplasts cultured in agarose-solidified medium. Cell cycle analysis of petioles and freshly isolated protoplasts showed that the latter has a significantly higher proportion of nuclei in G1 phase. Protoplasts did not initiate DNA synthesis or mitosis within the first 24 hours of culture. Low-frequency regeneration of shoots from protoplast-derived callus was accomplished on MS medium containing 1.0 mg ldnetin/liter when preceded by MS medium modified to contain only (in mg·liter-1) 800 NH4NO3, 1400 KNO3, 0.5 2,4-D, 0.5 kinetin, and 1.0 ABA. Roots produced from protoplast-derived callus formed adventitious shoots after 4 weeks on MS medium containing 2% sucrose, 0.02 mg kinetin/liter and 0.2% Gelrite. Secondary shoot formation from regenerated roots will be a more effective means of obtaining plants from protoplasts than direct shoot regeneration from callus. Chemical names used: silver thiosulfate (STS): 2.6-dichlorobenzonitrile (DB); fluorescein diacetate (FDA): 2.4-diacetate (FDA); 2.4 dichlorophenoxyacetic acid (2,4-D); abscisic acid (ABA).

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Xuhong Zhou, Xijun Mo, Yalian Jiang, Hao Zhang, Rongpei Yu, Lihua Wang, Jihua Wang, and Suping Qu

Peloquin, 1975 ), and desynapsis ( Ramanna, 1983 ; Veilleux, 1985 ). Entry into either mitosis or meiosis requires high cyclin-dependent kinase ( CDK ) activity, which is achieved by cyclins of the A and B groups in A. thaliana ( Francis, 2007 ; Inzé

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Brian M. Schwartz, Ryan N. Contreras, Karen R. Harris-Shultz, Douglas L. Heckart, Jason B. Peake, and Paul L. Raymer

together. ( D ) 11-TSP-1 paspalum in prometaphase of mitosis. Only 1450 of the 8000 Experimental Hybrid 2 seeds germinated (18.1%) within 3 months after treatment with the 0.1% colchicine + 2.0% DMSO solution. Initial flow cytometry analysis of this group

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Yang Hu, Chao Gao, Quanen Deng, Jie Qiu, Hongli Wei, Lu Yang, Jiajun Xie, and Desheng Liao

sporogenous cells and primary parietal cells were produced through the mitosis of the sporogenous cells, which formed two layers of the anther wall. ( A4 ) Local enlargement of the box in the A3. ( B1 ) The primary parietal cells underwent mitosis to produce

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Dongmei Wei, Chao Gao, and Deyi Yuan

calcium is associated with critical events of mitosis in plant cells. After the microspore divided to produce a bicellular pollen grain, the large vacuole in the vegetative cell disaggregated and calcium precipitates reappeared in the vegetative cell

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Shujuan Yang, Li Peng, Han Bao, and Huiqiao Tian

, rich in organelles, were pushed to the edge of the cell. ( F ) After mitosis, the microspore produced a large vegetative nucleus and a small generative cell, which is the bicellular pollen. The original generative cell that is semispherical clung to the

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Jessica DiMatteo, Lauren Kurtz, and Jessica D. Lubell-Brand

pollen grain; GE = germinated pollen grain. Discussion We observed two different pollen grain sizes, large and small. The difference in pollen grain size could indicate that large grains had undergone microspore mitosis I, which can result in increased