摘要:

Colchicine treatment of sorghum seedlings of both F1hybrids and of their pollen parent lines resulted in complex mutant plants the majority of which were true‐breeding. Recessive irradiation‐induced characters originally homozygous in the pollen parent lines and heterozygous in the hybrids did not appear in any of the mutants or their self progenies. Recessive normal characters apparently absent in the pollen parent lines and heterozygous in the hybrids appeared in some mutants and bred true in their self progenies. These results are consistent with the hypothesis that colchicine‐induced mutants arise through chromosome substitution (Sanders and Franzke, 1964, Jour. Arnold Arb. 45: 36). Since sorghums with 2n= 20 are believed to be of polyploid derivation, interchangeable chromosomes carrying different alleles could be present in true‐breeding lines. There is evidence that diploidmutantcomplements may result from reduction of polyploid nuclei. Since the proportion of true‐breeding mutants was as large from the highly heterozygous seedlings as from the homozygous seedlings, segregation of chromosomes during reduction must be primarily by c‐pairs which later separate as the homologues of a new cell. Plants from such cells would be equivalent to doubled haploids. With colchicine treatment, true‐breeding lines have been obtained from multiple hybrids in a single step rather than after many generations of selling.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06778.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The multiplication of the algaScenedesmus quadricaudais inhibited by Amitrole (3‐amino‐1,2,4‐triazole). This inhibition is reversed by addition of adenine to the growth medium. An electron‐microscopic study has been made of the cytological changes which accompany the inhibition by Amitrole and the subsequent reversal. In the presence of Amitrole the cells accumulate a large quantity of starch which is lost very rapidly as soon as the Amitrole block is released and cell multiplication is resumed.3Present address: Department of Biology and Botany, University of British Columbia, Vancouver, Canada.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06779.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Development of the epicotylary meristem is delayed; thus, it apparently has no immediate controlling influence on the procambium initiation either in the hypocotyl‐root axis or in the cotyledons. Contrary to the situation found in most herbaceous dicotyledons, the procambium forms a hollow cylinder in the axis of the mature embryo. The first protophloem differentiates simultaneously in the upper part of the hypocotyl‐root axis, at the base of the cotyledons, and in the cotyledons; protoxylem differentiation follows the same pattern as that of the protophloem. The direct vascular connection between the hypocotyl‐root axis and cotyledons is established early in the mature embryo, and the fundamental aspects of transition phenomena are exhibited by the procambium before mature vascular elements differentiate. In the mature embryos, the pattern of lateral differentiation is irregular in that the number of protoxylem elements present at different levels is quite variable.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06780.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The composition and ultrastructure of the synergids of cotton were studied. The cells were found to be surrounded by a partial wall composed of cellulose, hemicellulose, and pectins. The structure of the wall was observed to consist of an unusual fibrillar arrangement. The filiform apparatus was demonstrated to be an extension of the wall at the micropylar end of the cell. Large amounts of ER surround the filiform apparatus. Also associated with the latter are large numbers of plastids and mitochondria. The nucleus is large and contains a single, large nucleolus and, frequently, 1 or more micronucleoli. The nuclear membrane contains membrane‐bound vesicles but has few extensions into the cytoplasm. The ER is oriented parallel to the long axis of the cell and decreases in concentration from the micropylar to the chalazal end of the cell. Dictyosomes are common throughout the cell but are more numerous in the midportion where they are closely associated with the ER. The chalazal end of the cell is occupied by vacuoles rich in an inorganic compound which leaves a considerable residue of ash. Spherosome‐like bodies are common throughout the cell. Both the plastids and mitochondria show evidence of division. Ribosomes are numerous and are both free and associated with the ER, nucleus, plastids, and mitochondria. The function of the synergids is proposed to be the absorption, storage, and transport of compounds from the nucellus. On the basis of this function, it is suggested that the synergids act by providing material to the egg and the developing embryo and endosperm and that they are involved in the growth of the pollen tube into the embryo sac.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06781.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Primarily on the basis of aperture structure, 31 species ofHedyotissubg.Edrisia(Houstonia) are separable into 5 palynological groups. Group 1 is characterized by a simple os circumscribed by varying nexinous thickenings, groups 2–4 combine this os with a crassimarginate one to form a compound os, while group 5 is known only with the crassimarginate os. The first type is considered primitive, the compound os specialized and more advanced, and the third type reduced and highly advanced. Other characteristics of the pollen, including size and shape, aperture number, thickness of sexine and nexine, and reticulum, are discussed in relation to the apertures, and their probable primitive and advanced expressions are outlined. The data agree with the phyletic trends found in the sporophyte on the basis of results from morphology, chromosome number and size, and distribution, and they support and add to an earlier phylogenetic scheme proposed for the subgenus. The evidence from palynology also supports the treatment ofHedyotisandHoustoniaas congeneric.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06782.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The morphological changes which the stem apex undergoes in the course of photoperiodic induction are described and presented photographically in order to provide a basis for subsequent physiological investigations. In both a short‐dayNicotiana(N. tabacumcultivar ‘Maryland Mammoth') and a long‐day one (N. sylvestris), the vegetative meristem is narrow and flat. It becomes wider and dome‐shaped when flower induction has become irreversible. The speed at which the various morphological steps succeed each other varies with the intensity of light during the day, especially in the case ofN. sylvestris.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06783.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Chlorogenic acid and its 2 isomers, believed to be the 4– and 5–0‐caffeoylquinic acids, have been extracted from leaves of photoperiodic species ofNicotiana,separated by column chromatography (gradient elution) and measured quantitatively during the course of photoperiodic induction. In bothN. tabacumcultivar ‘Maryland Mammoth’ (a short‐day plant) andN. sylveslris(a long‐day plant), the change of the meristem from the vegetative to the flowering shape is preceded by a rise in the chlorogenic acid content of the leaves. During the differentiation of the flower primordia in the shoot apex, there is a drop in the concentration of the chlorogenic acid in the leaves, which is especially marked in the short‐day species. The levels of the 2 isomers decrease also at that time. There is no change in the ratios of the 3 caffeoylquinic acids during photoperiodic induction. In both the long‐ and the short‐day species, the 3‐isomer (chlorogenic acid) is present at the highest concentration. In the short‐day species, there is more of the 4‐isomer than of the 5‐isomer, whereas in the long‐day species, the level of the 5‐isomer equals or surpasses that of the 4–0‐caffeoylquinic acid.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06784.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Germination of seed ofPhacelia tanacetifoliais inhibited by several mechanisms. In addition to physical restraints imposed by the seed coats, the seed contains a water‐soluble inhibitor which is independent of light or temperature for its activity. Available evidence also points to the presence of 1 or more light‐activated inhibitors which are not easily leached from the seed. The blue‐light‐activated inhibition can be negated by high oxygen tensions or mechanical abrasion of the micropylar end of the seed. The suppression of germination by far‐red or red light can be negated by abrasion but is only partially reversed by oxygen. Combinations of abrasion and high oxygen tensions negate both light‐induced and temperature‐induced inhibitions of germination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06785.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Vegetative propagation and dispersal were studied in attached and detached increase bulblets ofAllium neapolitanum.The bulblets were sown in 3 positions (upright, horizontal, and inverted) at various depths, and the directions of the contractile roots and movement in the soil were calculated. A thick contractile root develops spontaneously from the base of the bulblet, irrespective of planting level, even at normal depth. The root is ageotropic and its direction is chiefly determined by the bulblet position. It generally develops at a plane perpendicular to the longitudinal axis of the bulblet. Thus, in upright and inverted bulblets, the root is horizontal, while in horizontal ones it may grow in various directions but always on the plane perpendicular to the axis of the bulblet. Depth has a marked effect on the direction of the contractile roots, diverting them from their original route (upwards in deep‐seated plants and downwards in shallow ones). Thus, the vegetative dispersal ofAllium neapolitanumis tridimensional, within definite soil levels.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06786.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The septal pores of homokaryotic and dikaryotic mycelia ofCoprinus lagopushave the complex structure characteristic of certain Basidiomycetes. The edge of the pore is thickened and covered on either side by a dome‐shaped, perforated, membranous cap. However, in heterokaryotic mycelia in which nuclear migration was believed to be taking place, in addition to the complex pores, simple pores were also observed as well as various intermediate stages interpreted as steps in the breakdown of complex to simple pores. The simple pores may facilitate nuclear migration.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06787.x

出版商:Wiley    

年代:1965

数据来源: WILEY