Scielo RSS <![CDATA[Bragantia]]> http://www.scielo.br/rss.php?pid=0006-870519470008&lang=en vol. 7 num. 9-10 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[<B>A severidade de corte no sisal e analise tecnológica da fibra</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051947000800001&lng=en&nrm=iso&tlng=en In this paper it is presented a detailed fiber analysis of leaves of twenty mature sisal plants taken from four positions on the plant: 1) first developped leaves (75°); 2) leaves usually cut for fiber extraction (50°) ; 3) leaves adjacent to the central bud (25°) ; and 4) young leaves not yet unfolded from the central bud (0°). The results herein reported are against the prevailing opinion that the sisal leaf only matures after it has unfolded from the central bud. Neither the physical nor the chemical fiber characteristics were adversely affected even if cutting was carried out up to the very young leaves. This practice, however, cannot yet be advised, as it desirability also depends on the effects of the severe cutting upon the subsequent rate of growth of the new leaves. A cutting trial including the cut of all leaves every four months is still in progress. Preliminary results have shown that the plants of this treatment were able to develop eight leaves until the second cut, with an average fiber content of 3,7%. <![CDATA[<B>Observações citológicas em <I>Coffea</B></I>: <B>XI - Métodos de tratamento pela colchicina</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051947000800002&lng=en&nrm=iso&tlng=en O tratamento de sementes de Coffea canephora (2n=22), C. Dewevrei (2n=22) e C. arabica (2n=44), por soluções de colchicina de 0,15% a 0,60% produziu plantas com número duplo de cromossômios (2n=44 em C. canephora e C. Dewevrei e 2n=88 em C. arabica). O tratamento de gemas foliares por pasta de lanolina contendo 0,10 a 0,60% de colchicina não produziu resultado nessas mesmas 3 espécies. Elaborou-se um novo método de tratamento de ramos que pode ser aplicado para os casos em que a planta que se deseja "duplicar" seja estéril. É o caso dos híbridos entre C. canephora e C. arabica (2n=33) e da forma di-haplóide (monosperma) de C. arabica (2n=22), os quais nâo produzem sementes, ou, melhor, cujas raras sementes têm em geral um embrião com número variado de cromossômios. O método consiste em fazer com que ramos levados ao laboratório absorvam uma solução de colchicina pela sua parte cortada e em seguida sejam enxertados de forma usual. Através dêste método conseguiu-se obter uma planta com 2n = 66 cromossômios a partir do híbrido triplóide ; conseguiu-se ainda obter uma planta com 2n = 44 cromossômios a partir do monosperma (2n = 22). No primeiro caso eliminou-se a esterilidade quase completamente ; no segundo caso obteve-se uma transformação completa de esterilidade em fertilidade. Êste método aplica-se a outras plantas nas quais não é possível o tratamento de sementes e que fàcilmente se pode multiplicar pela enxertia.<hr/>Colchicine treated seeds of Coffea canephora (2n = 22), C. Dewevrei (2n = 22) and C. arabica (2n=44) produced plants with doubled chromosome numbers (2n = 44 in the first two and 2n = 88 in the last mentioned species)! The strength of the solutions varied from 0,15 to 0,60% ; the treatment was given when the seeds were already germinating. The immersion of seeds in the solution even for many days did not affect the embryo. Colchicine in lanolin (0,10 to 0,60%) did not produce doubling of chromosomes when applied to buds of the same three species. A new method has been devised for the treatment of sterile plants. This is the case of the triploid (2n = 33) hybrids between Coffea arabica and C. canephora and of the di-haploid (2n = 22) form of Coffea arabica known as the monosperma variety : both are highly sterile producing only a few round seeds whose embryos are of varied chromosome numbers. The method is the following : twigs of the plants are taken to the laboratory where they are placed in individual vials containing a solution of colchicine ; after having absorbed a certain amount of the liquid, they are grafted. In the case of Coffee the strength of the solution was of 0,25 and 0,50%. Through this method, 66 - chromosome branches have been obtained on these grafts by treating original triploid (2n=33) tissue. Many 44 - chromosome branches were also obtained from a di-haploid (2n=22) variety. In the first case the sterility was almost entirely eliminated ; in the second case a complete change from sterility to fertility has occurred. This method is also applicable to other plants, when the treatment of seeds is not possible and grafting is an usual means of propagation.