摘要:

Weier, T. E., and W. W. Thomson. (U. California, Davis.)Membranes of mesophyll cells of Nicotiana rustica and Phaseolus vulgaris with particular reference to the chloroplast.Amer. Jour. Bot. 49(8): 807–820. Illus. 1962.—The endoplasmic reticulum in mesophyll cells is represented by short lengths of irregularly disposed, paired membranes. It is occasionally associated with a typically double nuclear envelope. Groups of irregularly parallel, paired membranes suggesting disorganized dictyosomes occur infrequently. Mitochondria are unevenly distributed in mesophyll; they are large and have sparse tubular cristae around their periphery. In the great majority of instances the bounding membrane is diffusely stained with KMnO4. When it is sharp and distinct, it may be double as usually pictured, or it may have well‐delineated stretches of a single membrane bounding 25–50% of its circumference. The tonoplast and ectoplast are very fragile, the former appearing as a single dark line. In young leaves the ectoplast is visualized as a continuous single membrane adjacent to the cell wall, but in our micrographs of mature leaves it is always discontinuous. The plastid membrane sometimes is distinctly double, having 2 dark components bounding a light component. In the great majority of cases, however, this membrane is either a solid dark line, or the clear component of the double membrane is crossed by delicate dark lines giving the membrane a braided, or scalariform appearance. The various appearances of the membrane may intergrade with each other. The width of the plastid membrane is variable, ranging from 200 to 400 A. The inner component may invaginate into the stroma, and bodies may form in the clear space between the 2 outer membrane components. Micrographs suggest that these bodies, and others formed by small masses of stroma, may be expelled into the hyaloplasm, where they exist as spherical single‐membraned particulates. The reality of the variable structure of the plastid membrane is discussed in light of concepts of membrane activity, molecular structure, and the relation of these factors to possible artifacts.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15013.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Scott, FloraMurray, B. G. Bystrom, and E. Bowler. (U. California, Los Angeles.)Cercidium floridum seed coat, light and electron microscopic study.Amer. Jour. Bot. 49(8): 821–833. Illus. 1962.—The structure of the seed coat of the desert treeCercidiumis typical of the family Leguminosae, but the inner integument is mucilaginous. The characteristic palisade cells of the epidermis and the many‐armed cells of the mucilaginous zone are discussed in detail. The minute wax rodlets on the surface of the young seed fuse later into a film of wax. The epidermal palisade cells are polygonal in transection and the walls are strengthened by cellulose flanges. The palisade cells are enclosed in a thin suberin‐like sheath which connects with the film which lines all air‐filled intercellular spaces in the outer integument. Plasmodesmata extend from the protoplast through the subcuticular zone to the cuticle and also interconnect with adjacent cells through numerous pits in the interflange areas of the main wall. The cells of the inner integument are many‐armed. Intercellular spaces at all stages of growth observed are occluded with mucilage; nevertheless, they are lined with a suberin‐like film similar in reaction to that of the air‐filled intercellular spaces of the outer integument. The distribution of wall materials and ergastic substances was determined by microchemical tests. For electron microscopic study, the epidermis and the mucilaginous zone were fragmented ultrasonically, after chemical treatment when necessary. Cuticular fragments, frequently polygonal in outline, are dense to the electron beam at photographic illumination. When exposed to the electron beam, full‐strength, volatile components are driven off and condense on other wall fragments or on substrate. Unique structures occur in the subcuticular zone, termed here, collar, cone and paddle structure. The basic material of the cell wall as a whole is cellulose impregnated with matrix materials, mainly non‐cellulosic polysaccharides. In addition, lipid‐like substances are conspicuous particularly in the flanges of the palisade cells. Under the electron beam, full‐strength, these substances volatilize and leave the flanges with a blistered outline except in the region of the light line. The volatile substances may be absent from this zone or the microfibrillar structure may prevent distortion. The microfibrillar pattern throughout the length of the flanges is dominantly parallel, but a change to reticulate arrangement occurs in the light‐line region. Numerous pits mark the paths of the plasmodesmata in the subcuticular zone and also through flange and interflange areas of the wall. The dominant microfibrillar pattern in the mucilage cells is reticulate in young and old cells, except for helical orientation in extending arms. Pits occur on arm ends but are infrequent elsewhere. The loose microfibrillar structure presumably allows continuous secretion of mucilage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15014.x

出版商:Wiley    

年代:1962

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15015.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Marinos, NicosG. (Waite Agric. Res. Inst., Adelaide, S.A., Australia.)Studies on submicroscopic aspects of mineral deficiencies. I. Calcium deficiency in the shoot apex of barley.Amer Jour. Bot. 49(8): 834–841. Illus. 1962.—The apical dome of the shoot apex of barley, or other cereals, is suitable for the study of submicroscopic cytological changes induced by specific mineral deficiencies because of the many uniform cells available. Also, the well‐defined stages of development of the entire apex make possible, in certain cases, the correlation between growth responses and changes in cell structure. The ultrastructure of shoot apex meristematic cells, after KMnO4fixation, is fundamentally similar to that of root meristems. The effects of Ca deficiency on cell ultrastructure appear rather suddenly and it has not been possible to reveal unequivocably the initial sequence of events. The first indisputable signs of structural abnormalities appear when the nuclear envelope and the plasma and vacuolar membranes break up and “structureless areas” appear in the cells, followed by the disorganization of other structures like mitochondria and Golgi apparatus, while plastids are more persistent although eventually they also disintegrate. With the progress of Ca deficiency, the cell walls stain darker and gaps may appear, indicating a weakening of their structure. This evidence suggests that Ca is essential for the maintenance and probably for the formation of cell‐membrane systems on which the functional integrity of cell metabolism is dependent; Ca effects on cell walls are probably secondary to those changes already described.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15016.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Koller, D. (The Hebrew U., Jerusalem.2)Preconditioning of germination in lettuce at time of fruit ripening.Amer. Jour. Bot. 49(8): 841–844. 1962.—The effects of controlled environments during maturation on subsequent germination response of the seed were investigated with the light‐sensitive lettuce ‘Grand Rapids.‘ The plants matured under a variety of temperature/photoperiod combinations, after completing vegetative growth and flower initiation under identical conditions. Good seed set was obtained only at night temperatures between 17 and 23 C, under short‐day (8‐hr) conditions. Seed germination was tested at 20, 23 and 26 C, in continuous dark and after a light‐break, respectively. The conditions under which the seed had ripened brought about quantitative changes in the germination response. The stimulating effects of a light‐break on germination at high temperatures did not change, but maturation under high temperatures or in continuous light increased the high‐temperature tolerance of seed germination both in continuous dark and after a short light‐break.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15017.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Abbott, IsabellaA. (Hopkins Marine Sta. of Stanford U., Pacific Grove, Calif.)Morphological studies in a new species of Acrosymphyton (Rhodophyceae).Amer. Jour. Bot. 49(8): 845–849. Illus. 1962.—Acrosymphytontaylorisp. nov. (Dumontiaceae, Cryptonemiales, Rhodophyceae) is shown to have a sexual cycle essentially similar to that of the 2 other species in the genus, but differs in some details of the sexual structures and the vegetative structure.Acrosymphyton taylori, from the Hawaiian Islands, is the only member of the genus from the Pacific.Acrosymphytonis only one of several genera of red algae possessing soft, gelatinous, uniaxial thalli. A study of specimens from various herbaria showed that specimens ofDudresnayaandCalosiphoniahave been confused withAcrosymphyton.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15018.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Soderstrom, ThomasR. (Smithsonian Institution, Washington, D.C.)The isocitric acid content of crassulacean plants and a few succulent species from other families.Amer. Jour. Bot. 49(8): 850–855. 1962.—The leaves of 58 species of plants were assayed for isocitric acid content by the highly specific enzymatic method of Grafflin and Ochoa (1950). These species included 39 from the family Urassulaceae in addition to 19 species of succulents representing 8 families and 12 genera. With but one exception(Echeveria derenbergii), isocitric acid was found in relatively large concentrations in the leaves of all crassulacean species examined, and was recorded for the first time in 5 genera of this family. Isocitric acid was found in 2 genera of the Liliaceae and in 1 genus of the Piperaceae, families in which it previously had not been known to occur. The presence of substantial concentrations of isocitric acid in the leaves appears to be characteristic of the family Crassulaceae and of certain genera in other widely unrelated families. There is no indication, however, that the concentrations of this acid in the leaves of species and genera of the Crassulaceae is correlated with their affinities based on morphology.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15019.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Lewis, WalterH. (Stephen F. Austin State Coll., Nacogdoches, Texas.)Phylogenetic study of Hedyotis (Rubiaceae) in North America.Amer. Jour. Bot. 49(8): 855–865. Illus. 1962.—Chromosome numbers for 39 taxa ofHedyotisseparable into the subgeneraEdrisia(Raf.) Lewis andOldenlandia(L.) T.&G. are reported. The occurrence of basic numbers ofx= 6, 7, 8, 9(10), 11, and 13, including infraspecific aneuploidy inH. nigricans(Lam.) Fosb., illustrates the importance of aneuploidy in the speciation ofHedyotisin contrast to most rubiaceous genera. In the North American subg.Edrisia, 25 species are ranked according to primitive and advanced expressions for 13 characters. It is postulated on the basis of these, ecologic, geographic, and chromosomal data that thex= 11 group gave rise to thex= 13 line by the gain of chromosomes and to thex =(10)9, 8, and 7 groups by reduction. Those species with a basic number of 6 are thought to have an Asian origin. Although aneuploidy has been dominant in the evolution of subg.Edrisia, only 12% of the species are polyploids. The development of polyploid races in 3 species,H. caerulea(L.) Hook.,H. polypremoides(Gray) Shinners, andH. purpurea(L.) T.&G., however, suggests a greater role of polyploidy in the current evolution ofHedyotis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15020.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Whittingham, W. F. (U. Wisconsin, Madison.)The inheritance of acenaphthene tolerance in Neurospora sitophila. Amer. Jour. Bot. 49(8): 866–869. 1962.— Acenaphthene‐tolerant strains ofN. sitophila, a species that normally does not grow in the presence of the fungistatic hydrocarbon, were isolated. The growth rates of the tolerant strains were less than those exhibited by the parental cultures, especially when acenaphthene was present in the medium. However, the tolerant character was stable for at least 5 generations and apparently resulted from a single‐gene mutation as judged from mating experiments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15021.x

出版商:Wiley    

年代:1962

数据来源: WILEY

摘要:

Klein, RichardM. (New York Bot. Gdn., New York, N.Y.), and Deana T. Klein.Interaction of ionizing and visible radiation in mutation induction in Neurospora crassa.Amer. Jour. Bot. 49(8): 870–874. 1962.—Conidia of the purple adenineless strain ofN. crassawere irradiated with 25 kr of X rays and then exposed to far‐red or red radiations or to far‐red followed by red radiation. Far‐red light, without effect on un‐irradiated conidia, augmented the genetic damage caused by X rays as measured by survival (colony count), back mutation to adenine prototrophy, and the induction of mutants affecting colony morphology. Post‐X‐irradiation with red light ameliorated the severity of X‐radiation as measured by survival and back mutation. The potentiation of X‐ray‐induced genetic damage by far‐red light could be completely negated by subsequent exposure to red light.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1962.tb15022.x

出版商:Wiley    

年代:1962

数据来源: WILEY