摘要:

Chromosome counts for 30 collections representing 21 species examined by the authors are reported. Of these, eight species counts are a first report; the others are confirmation of earlier reports. The genusDesmodiumis shown to be dibasic with base chromosome numbers ofx= 10 andx= 11.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06886.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Adventitious roots on branches ofTamarix aphylla(L.) Karst. develop in hyperhydric outgrowths of the lenticels. The following stages could be distinguished in the formation of the apices of these roots: (1) initiation, (2) a stage of random divisions, (3) a stage of transverse divisions, with respect to the longitudinal axis of the primordium, (4) formation of the procolumella, (5) differentiation of the procambium, the cortical meristem and the protoderm, (6) enlargement of the promeristem, and (7) emergence.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06887.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Examination of genera of the Pseudoascoboleae (Ascomycetes, Discomycetes, Ascobolaceae) revealed that many were polytypic. Characters presently used to distinguish these genera are considered to be artificial and true relationships cut across accepted generic lines. Of the genera treated,Thecotheusand parts ofAscophanus, since their asci blue in iodine and their spores bear callose‐pectic markings, are considered more closely related to the Pezizeae. Other genera are excluded from the Pseudoascoboleae because of other striking characters. Since the Pseudoascoboleae is shown to be an artificial grouping, it is proposed to abandon the name, using instead the tribe name Theleboleae, placed in the Pezizaceae rather than the Ascobolaceae, for all of those genera with asci that do not blue in iodine, with smooth, elliptical spores without oil guttules, and with eight‐spored and multispored species. Four new genera are described:Iodophanus, for species ofAscophanuswith iodine‐positive asci;Coprotus, for segments ofAscophanusandRyparobius; Caccobius, for species intermediate toAscozonusandThelebolus;andTrichobolus, for the setose members ofThelebolus.The species ofRyparobiusnot belonging toCoprotusare transferred toThelebolus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06888.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Polyploidy was induced in twoMusaspecies and their hybrid by means of immersing newly germinated diploid seedlings in 0.5% aq. colchicine solution. TetraploidM. balbisianaplants were taller and more robust but had slower growth rate, droopier leaves, fewer suckers, and scantier root systems than the diploids. Tetraploidy affected fruit size and shape inM. balbisianaand inM. acuminata.Tetraploidy did not affect bunch size (the number of fruit‐bearing nodes) inM. acuminata banksiibut caused great reduction in bunch size ofM. acuminata microcarpa‘Zebrina.’ Doubling of the chromosome number resulted in doubling of the anthocyanin concentration in the leaves of the pigmented banana plants. Colchicine‐induced female sterility was detected in a treated diploid plant ofM. acuminatasubsp.microcarpa.A number of either female or male, or both female and male sterile plants were encountered in colchicine‐induced tetraploidM. acuminataspecies. Only one secondaryM. balbisianatetraploid plant was found to be partially female sterile. Colchicine treatment of the seedlings resulted in chromosomal irregularities at mitosis. Chromosomes appeared as open chains, rings and multiple configurations at metaphase. In the majority of cases doubled chromsomal complements reverted to their original number. However, there were cases in which diploids were induced to tetraploidy and later reverted to triploidy instead of diploidy. Also, there were cases in which triploids were doubled to hexaploidy and later reverted to tetraploidy instead of triploidy. From the close morphological similarity between a number of triploid and tetraploidM. balbisianaplants and some edible triploid cultigens belonging to the “ABB Group,” it is suggested that the karyotype of some of these cultigens could be “BBB” rather than “ABB” which contains one “A”M. acuminatagenome. New pathways and additional evolutionary possibilities are incorporated into Simmonds’ scheme on the evolution of edible bananas.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06889.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Aspergillus heterothallicusK., F. and R., isolated from Costa Rican soils, represents the first species in this genus that is truly heterothallic. Each of the eleven strains investigated is functionally hermaphroditic but self‐sterile and falls into one of two cross‐mating classes,Aora.The mating‐type factorsAandaappear to be an allelic pair segregating independently of the locus for pigmentation of mycelium which varies from yellow to pinkish orange in different isolates. The striking variation in the development of hülle cell masses that occurred among the progeny from the cross WB 5096(A) × WB 5097(a) was found to be genetically controlled. The gene responsible for a delay in the formation and maturation of cleistothecia appeared to be loosely linked to theamating‐type locus and could be recombined into theAmating type. The mechanism of fertilization has not been completely elucidated. Coiled ascogonia were found within young hülle cell masses developed in cultures where two isolates of opposite mating types were crossed; such coils have not been observed, thus far, within hülle cell masses in unmated cultures. Although no recognizable male structure has been found, the fertilizing element appears to be mycelial in form rather than conidial. Interspecific mating did not occur when strains ofAspergillus heterothallicuswere paired with other members of theA. nidulansgroup.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06890.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Heterokaryon compatibility between strains ofAspergillus heterothallicuswas tested by using prototrophic mutants of contrasting conidial head colors obtained by ultraviolet radiation. Heterokaryons were formed between mutants only when two conditions were fulfilled: The mutants had to be of the same mating type, and the isolates from which the mutants were derived had to be of similar macroscopic growth characteristics and mycelial pigmentation. Heterokaryotic heads were conspicuously striate, being composed of spore chains pigmented as the parental types, and representing, in most cases, examples of an “autonomous” nuclear action. Heterokaryotic heads of unusual interest, resulting from “autonomous‐nonautonomous” type of gene actions, were produced in combinations of a pinkish tan (PT) mutant. The nuclear action of thePTmutant was nonautonomous regardless of the type of mutant with which it was paired, whereas the nuclear action of the other head‐color mutants was autonomous. Genetic analyses of head‐color mutants were conducted by using all possible crosses between mutants derived from strains WB 4982 (Amating type) and WB 5086 (a mating type). It was found that similar color mutations of these two strains were allelic. All mutations responsible for different head colors, however, were found to be nonallelic to each other. The interactions between the different head‐color mutants were studied in double mutants formed in the aforementioned crosses. Epistatic‐hypostatic relationships between the different mutations were determined, and such relationships were used in the construction of a possible biosynthetic sequence leading to the production of the wild‐type (green) pigment of conidial heads. The main sequential steps for the biosynthesis of conidial pigmentation appear to proceed from white to yellow, to brown, to brownish green, and to green.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06891.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Ulex europaeusis a much‐branched shrub with small, narrow, spine‐tipped leaves and axillary thorn shoots. The origin and development of axillary shoots was studied as a basis for understanding the changes that occur in the axillary shoot apex as it differentiates into a thorn. Axillary bud primordia are derived from detached portions of the apical meristem of the primary shoot. Bud primordia in the axils of juvenile leaves on seedlings develop as leafy shoots while those in the axils of adult leaves become thorns. A variable degree of vegetative development prior to thorn differentiation is exhibited among these secondary thorn shoots even on the same axis. Commonly the meristems of secondary axillary shoots initiate 3–9 bracteal leaves with tertiary axillary buds before differentiating as thorns. In other cases the meristems develop a greater number of leaves and tertiary buds as thorn differentiation is delayed. The initial stages in the differentiation of secondary shoot meristems as thorns are detected between plastochrons 10–20, depending on vigor of the parent shoot. A study of successive lateral buds on a shoot shows an abrupt conversion from vegetative development to thorn differentiation. The conversion involves the termination of meristematic activity of the apex and cessation of leaf initiation. Within the apex a vertical elongation of cells of the rib meristem initials and their immediate derivatives commences the attenuation of the apex which results in the pointed thorn. All cells of the apex elongate parallel to the axis and proceed to sclerify basipetally. Back of the apex some cortical cells in which cell division has persisted longer differentiate as chlorenchyma. Although no new leaves are initiated during the extension of the apex, provascular strands are present in the thorn tip. Fibrovascular bundles and bundles of cortical fibers not associated with vascular tissue differentiate in the thorn tip and are correlated in position with successive incipient leaves in the expected phyllotactic sequence, the more developed bundles being related to the first incipient leaves. Some secondary shoots displayed variable atypical patterns of meristem differentiation such as abrupt conversion of the apex resulting in sclerification with limited cell elongation and small, inhibited leaves. These observations raise questions concerning the nature of thorn induction and the commitment of meristems to thorns.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06892.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Three‐day‐old seedlings of ‘Atlas’ barley were treated for 1 hr with an aqueous solution of 2‐mercaptoethanol at various concentrations. This caused a general delay of mitosis, suppression of subsidiary cell formation in manystomatal complexes, and complete inhibition of the formation of some stomatal complexes. In a small proportion of stomatal complexes the orientation of the division of the guard cell mother cell was changed so that its mitotic spindle was no longer transverse but parallel to the long axis of the leaf and produced daughter cells proximally and distally to each other. The highest frequency of such proximal‐distal orientations, a mean of 2.23 per stomatal row, was produced by concentrations of 0.175–0.2 m. Proximal‐distal reorientations were concentrated in a region of the leaf distal to that in which the greatest inhibition of stomatal complexes occurred. Susceptible complexes were those at early stages of subsidiary formation when exposed to mercaptoethanol; this is long before prophase of GCMC division. The mean length/width ratio of cells at this stage was significantly greater in treated than in control material. Gibberellic acid at 550 ppm significantly increased both the 1/w ratio and the frequency of proximal‐distal divisions. A much higher proportion of proximal‐distal divisions was obtained in upper leaf sheaths excised and placed for 24 hr in a moist atmosphere. This effect was associated with a period of quiescence following excision, after which mitoses were resumed, many of them with proximal‐distal reorientation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06893.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

The zoospore ofBlastocladiella emersoniihas been re‐examined with the electron microscope. The following new findings were made. A double unit‐membrane system surrounds all cell organelles except γ‐bodies, vacuoles and a few fragments of membranes. Lipid granules on one side of the large mitochondrion alternate with vesicles. The kinetosome of the posterior flagellum does not have any central fibrils as previously reported; a small, cylindrical structure is found within its anterior end. An associated centriole is located next to the kinetosome. Three striated rootlets pass from the kinetosome by separate channels through the mitochondrion. There appears to be no connection between the striated rootlets and the mitochondrion. Microtubules originating at the anterior end of the kinetosome pass into the cytoplasm between the mitochondrion and the nuclear cap. Long, dense strands were observed in some nuclei. The axoneme is taken up into the spore during encystment and is found in the freshly encysted spore. No trace of the flagellar sheath has been found in the encysted spore.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06894.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Three hybrids ofA. repens, 2n= 42, ×A. spicatum, 2n= 28, and two reciprocal hybrids were obtained from emasculated and unemasculated crosses, respectively. The 35‐chromosome hybrids tended to be morphologically intermediate between the parent species but resembledA. repensmore closely thanA. spicatum. A. repensbehaved cytologically as a segmental autoallohexaploid, andA. spicatumacted cytologically as an autotetraploid. Mean chromosome associations of 8.04 I, 12.72 II, 0.41 III, 0.06 IV, and 0.009 V were observed in 116 hybrid cells at metaphase I. Most chromosome pairing in the hybrids was attributed to autosyndesis.A. spicatum, A. repens, and their hybrids were represented by genome formulas of SSSS, R1R1X1X1X2X2, and SSR1X1X2, respectively. Hybrid fertility ranged from 0.02 to 0.69 seeds per spikelet.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb06895.x

出版商:Wiley    

年代:1967

数据来源: WILEY