Dixier M. Medina

Observações citológicas em Coffea: XIV - Microsporogênese em Coffea arabica L. Var. rugosa K.M.C.

Only one plant of Coffea arabica L. var. rugosa K.M.C., is available for study Its fruit production is very low. Of the progeny observed, none has reproduced th rugose condition of the leaves characteristic of the parent plant. Previous study ha shown that the rugose condition of the leaves could not be considered a somatic chimer because the tissues have a normal number (2n=44) of chromosomes. The present cytological study was undertaken in order to find out if the low yiel of the rugose variety could be related to abnormalities in microsporogenesis. The structure of the chromosomes in early prophase is difficult to study. In diaki nesis two pairs and sometimes three pairs of chromosomes appear to be attached to th nucleolus. Also in diakinesis it is possible to locate the centromere in the chromosoni pairs and to count the chiasmata. It was observed that an average of 6.6 bivalent show one single chiasma, 12.3 bivalents show two chiamata and 3.0 bivalents shoM three chiasmata. The average total number of chiasmata per cell at this phase is o 40.0, while at metaphase this number is reduced to 34.7. The first division in the mi crospore is normal and the resulting two nuclei differ in size and also in the size o their nucleolus. The polen grains are normal, giving 69% germination on a medium containinj 0,5% of agar and 15% of sucrose. It is concluded that microsporogenesis is normal and would not appear to be relate< to the low production of fruits of the rugosa variety. The fact that none of the progen1 has reproduced the rugose condition might be due to the limited number of plants observed.

O Endosperma de café como material para estudos citológicos

The endosperm tissue of the coffee seed was used successfully for chromosome countings, acetic orcein technique having proved satisfactorily to stain the well spread metaphasic and prophasic chromosomes. Endosperms with 62, 64, 66 and 68 chromosomes occur in the monosomic plants of C. arabica (n = 43) while only endosperms with 3n = 66 are formed in the typica variety (2n = 44). Polyploid cells with 128 and 132 chromosomes were also observed and this occurrence was probably the result of endomitosis. Direct observation of endosperm chromosomes gives the real cytological constitution of fertile gametes, the probable chromosome numbers of the progeny being inferred in advance.

Microsporogenesis in Diploid Species of Coffea L.

SUMMARYIn this paper are presented the observations on the microsporogenesis in the diploid (2 n = 22) species of Coffea: C. eugenioides Moore. C. liberica Hiern., C. Kapakata Hirsch, and C. racemosa Lour. These species displayed a regular meiotic behaviour in most pollen mother cells with formation of 11 bivalents.The average of 16 to 17 total chiasmata per cell in metaphase was found. Their distribution among the bivalents varied from cell to cell; a mean of one pair of chromosomes shows three chiasmata; three to four bivalents present two chiasmata; and finally a mean of six to seven pairs presents only one chiasma.Univalents, unequal chromosome distribution to the poles and laggards, which were seen in some cells, may be consequence of certain irregularities as for instance the lack of pairing of some chromosomes and to assinchronism in the anaphases.It has been found that there are variable but generally low amounts (3.19 to 14.61%) of irregular anaphases and also of abnormal tetrads (0.10 to 5.10%) ...

Efeitos de herbicidas na anatomia de capim-carrapicho e amendoim-bravo

Cenchrus echinatus L., seeded in pots at a depth of four cm, was treated with trifluralin at 0.84 kg/ha, incorporated at depths of 0 to 3 and 5 to 11 cm. Euphorbia heterophylla L, seeded at a depth of one cm, was treated with trifluralin at the same rate, incorporated from 0 to 8 cm, pendimethalin at 1.15 kg/ha and 2.4-D, amine, at 1.44 kg/ha at surface, in preemergence. The plants were observed during the two first weeks and after this material was collected and microscopic observations were made on the affected tissues. Trifluralin enlarged the root tip and the coleoptile diameter, inhibiting their growth in C. echinatus. Swelling of cortical cells was observed. The cells had thinner walls and sometimes were multinucleate. In E. heterophylla there was lateral root inhibition and little swelling of cortical cells. Pendimethalin caused great thickening of the transition zone in E. heterophylla, due to swelling of cortical and epidermal cells, which had thinner walls. Small lateral root inhibition occured. The 2.4-D affected tissue formation, originating cells in the pith center. In some plants an epidermal dislocation was observed.

Auto-incompatibilidade em Coffea Dewevrei de wild. et th. dur.

Pollination studies in Coffea Dewevrei De Wild, et Th. Dur. showed that this species is self-sterile. Several varieties of the group are now under investigation to explain such sterility. Only crosses between certain plants are fertile. Cytological investigation on the pollen and embryo sac development indicated that there is no abnormality that could prevent fertilization. Pollen behaves differently when it is placed on the stigmas of compatible and incompatible plants. Only in the first case does germination occur. All these facts led to the conclusion that self-sterility in Coffea Dewevrei is also of genetic origin, perhaps expressed in the same way as in C. canephora Pierre ex Frohner. The exact mechanism of this incompatibility is not known yet. The occurrence of empty locules have been recorded in case of several plants of the varieties Abeokutae, Dybowskii, Excelsa, and Dewevrei. These results are presented in this paper.

Novas observações citológicas no endosperma de café

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.

Microsporogênese em um híbrido tri-plóide de Coffea racemosa lour. x C. arábica L.

A natural hybrid of Coffea racemosa Lour. (2n= 22) and C. arabica L. (2n= 44) is triploid (2n= 33), intermediate in many characteristics between both species and highly sterile. Frequency of trivalents is smaller in the racemosa than in the canephora hybrid; bivalents, however, are more frequent in the racemosa hybrid. Other observations on mierosporogenesis are presented and discussed. New hybrids including other species should be obtained and studied before a definite conclusion be drawn as to taxonomical relationships of Coffea species.

Macrosporogênese, formação e desenvolvimento do saco embrionário, do endosperma e do embrião em Coffea Dewevrei De Wild, et Th. Dur

O desenvolvimento do saco embrionario nas flores de Coffea Dewevrei e um processo mais demorado do que em C. canephora e muito mais lento do que em C. arabica. As primeiras divisoes do megasporo funcional tem inicio no dia da abertura da flor, raros sacos embrionarios se apresentando completos no 1.° dia; em geral estao completos aos oito dias e, independentemente da fertilizacao, apresentam os nucleos polares fundidos 10 dias apos a abertura das flores. A fertilizacao se da a partir do 6.° dia, sendo mais comum a partir do 10.° dia. E tambem a partir do 10.° dia que ocorrem as primeiras divisoes do endosperma, que pode apresentar ate 20 nucleos antes de se tornar celular, e isto pode ocorrer dos 22 aos 107 dias. Somente depois que o endosperma se apresenta celular e que se da a l.a divisao na celula-ovo; e esta primeira divisao so foi observada aos 142 dias. Em ovulos dessa mesma idade foram observados pro-embrioes em estado um pouco mais adiantado de desenvolvimento. O crescimento do endosperma em volume e lento na primeira fase; o ovulo, no entanto, cresce rapidamente em seguida a fertilizacao, atingindo em media, aos 142 dias, um tamanho 1500 vezes maior que seu tamanho por ocasiao da abertura da flor. No mesmo espaco de tempo o endosperma torna-se, em media, somente 230 vezes o volume inicial. Mesmo na falta da fertilizacao o ovulo cresce ligeiramente durante os 30 primeiros dias; observam-se, porem, os sinais de degenerescencia do saco embrionario, que nao cresce. Em seguida, os tecidos do ovulo tambem degeneram e se isto ocorrer nos dois ovulos, o ovario se desprende da arvore; alguns chegam a se manter na planta ate 107 dias.

Hibridações entre Coffea arabica e C. kapakata. análise citológica de um híbrido triplóide

The ability of C. kapakata to cross with C. arabica was analysed in the present paper. The ratios between seed-ovules, seedling-seeds and seedling-ovules were taken into account in order to evaluate the kinhood of the two species. It was found that the crossing rate was higher when C. arabica, the tetraploid species, was used as female. In the backcrosses it was found that the hybrid could not be crossed with C. kapakata, while C. arabica crosses in both directions with the F, hybrid. The hybrids were morphologically intermediate to both species. Observations were made about the meiosis of one of the hybrids. The chromosome associations were in average 1.33III 9.45II and 10.07I, for diakinesis and first metaphase. The distribution of the chromosomes during anaphase as well as the tetrades are abnormal. The pollen grains contain more frequently from 13 to 17 chromosomes. The hybrids between C. arabica and C. kapakata have been used as bridge for transferring drought resistance of C. kapakata to the cultivars of C. arabica.

Nova técnica para a contagem de cromossomos em amendoim (Arachis Hypogaea L.)

The determination of the chromosome number in sections or smears of the peanut plant (Arachis hypogaea L.) is rather difficult because of the small number of cells with polar view of metaphase plates and for the tendency of the peanut chromosomes to clump together. Several techniques were tried in order to overcome these difficulties. The best results were obtained with the following method:(a) pre-treatment of the root tips in a saturated solution of paradichlorobenzene at 16-20°C for 4-8 hours or in a 0,002 M solution of oxyquinoline at 16°C for 6-7 hours; (b) hydrolysis in acetic orcein (2% orcein in 70% acetic acid) and hydrochloric acid in the proportion of 9:1; (c) smear and staining in 1% acetic orcein in 45% acetic acid,Paradichlorobenzene and oxyquinoline produce the c-mitotic effect on the chromosomes of Arachis. Consequentely the number of cells at metaphase is greatly increased and the chromosomes appear shortened and scattered throghout the cell. This makes the countings very easy. Comments about the mode of action of paradichlorobenzene on Arachis chromosomes are made and a detailed schedule of the technique is presented.