Data/hora: 24/09/2024 18:44:31

Biblioteca(s): 	Embrapa Gado de Corte.	
Data corrente: 	30/09/2009	
Data da última atualização: 	13/10/2009	
Autoria: 	RISSO-PASCOTTO, C.; PAGLIARINI, M. S.; VALLE, C. B. do; JANK, L.	
Afiliação: 	C. RISSO-PASCOTTO, UEM; MARIA SUELY PAGLIARINI, UEM; CACILDA BORGES DO VALLE, CNPGC; LIANA JANK, CNPGC.	
Título: 	Symmetric pollen mitosis I and suppression of pollen mitosis II prevent pollen development in Brachiaria jubata (Gramineae).	
Ano de publicação: 	2005	
Fonte/Imprenta: 	Brazilian Journal of Medical and Biological Research, Ribeirão Preto, v.38, n.11, p. 1603-1608, nov. 2005.	
Idioma: 	Português	
Conteúdo: 	Microsporogenesis and pollen development were analyzed in a tetraploid (2n = 4x = 36) accession of the forage grass Brachiaria jubata
(BRA 007820) from the Embrapa Beef Cattle Brachiaria collection that showed partial male sterility. Microsporocytes and pollen grains
were prepared by squashing and staining with 0.5% propionic carmine. The meiotic process was typical of polyploids, with precocious
chromosome migration to the poles and laggards in both meiosis I and II, resulting in tetrads with micronuclei in some microspores. After
callose dissolution, microspores were released into the anther locule and appeared to be normal. Although each microspore initiated its
differentiation into a pollen grain, in 11.1% of them nucleus polarization was not observed, i.e., pollen mitosis I was symmetric and the
typical hemispherical cell plate was not detected. After a central cytokinesis, two equal-sized cells showing equal chromatin condensation
and the same nuclear shape and size were formed. Generative cells and vegetative cells could not be distinguished. These cells did
not undergo the second pollen mitosis and after completion of pollen wall synthesis each gave rise to a sterile and uninucleate pollen grain.
The frequency of abnormal pollen mitosis varied among flowers and also among inflorescences. All plants were equally affected. The
absence of fertile sperm cells in a considerable amount of pollen grains in this accession of B. jubata may compromise its use in breeding and
could explain, at least in part, why seed production is low when compared with the amount of flowers per raceme.	
Palavras-Chave: 	Brachiaria jubata; Braquiária; Microsporogênese.	
Thesagro: 	Gramínea Forrageira; Melhoramento Genético Vegetal; Pastagem.	
Categoria do assunto: 	F Plantas e Produtos de Origem Vegetal	
Registro original: 	Embrapa Gado de Corte (CNPGC)	
Exemplares: 	CNPGC - (12812-1) - UPC - SP - PP -  -  - 463/12 - DIS