Novas observações citológicas no endosperma de café

Abstract

Contagens de cromossomos foram efetuadas em endosperma de algumas espécies de Coffea, empregando-se a técnica da orceína acética, já referida em trabalho anterior. Os resultados encontrados para C. arabica (variedades typica, semperflorens, 2n = 44, e plantas monossômicas, 2n = 43) ; C. canephora, 2n = 22, C. dewevrei, 2n = 22, C. eugenioides x C. kapakata, 2n = 22 e C. eugenioides duplicado, 2n = 44, são discutidos em cada caso. Em todo o material estudado foi constatada a endomitose. O endosperma é, no início, um tecido de constituição 3x, transformando-se depois num tecido quimérico com células polissomáticas de diferentes graus. As numerosas figuras conseguidas, que permitiram contagens ou microfotografias, confirmam que, no cafeeiro, o endosperma é um material favorável para pesquisas citológicas.

Chromosome countings have been rnade on lhe endosperm of Coffea using the same technique of acetic oreein already referred to in previous work of the author. Endosperm from the varieties typica and semperflorens (2n = 44) and monosomic plants (2n = 43) of C. arabica as well as of other species as C. canephora (2n = 22), C. dewevrei (2n = 22), C. eugenioides x C. kapakata (2n = 22) and duplicated C. eugenioides (2n = 44) were studied. Gametic number of chromosomes are discussed leading in some cases to the conclusion that gametes with missing chromosomes and gametes with supernumerary chromosomes were functional. Endomitosis was observed in all material studied. Endosperm tissue is constituted, therefore, by polysomatic cells (6x, 12x) in addition to the monosomatic ones (3x) initially formed through fertilization. The possible relation of endomitosis and embryo development is also discussed. The great number of photomicrographies obtained indicates once more that coffee endosperm is a favourable material for cytological investigations.