摘要:

Haber, AlanH., WilliamL. Carrier, and DonaldE. Foard. (Biol. Div., Oak Ridge Natl. Lab.,3Oak Ridge, Tenn.)Metabolic studies of gamma‐irradiated wheat growing without cell division.Amer. Jour. Bot. 48(6): 431–438. Illus. 1961.—Wheat grains given 800 kr of Co60gamma radiation before moistening can germinate and grow into small seedlings without cell division or desoxyribonucleic acid (DNA) synthesis. This growth is sustained by metabolism and is not merely water uptake. The growing seedlings increase in dry matter, protein, and ribonucleic acid (RNA). They can perform photosynthesis by fixing carbon from CO2into sugar phosphates, sucrose, amino acids, and organic acids. These results suggest that such irradiated cereals may be used for certain physiological and anatomical studies of germination and development in an intact growing organism in the absence of DNA synthesis, mitosis, and cell division.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11664.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Foard, DonaldE., and AlanH. Haber. (Biol. Div., Oak Ridge Natl. Lab.,3Oak Ridge, Tenn.)Anatomic studies of gamma‐irradiated wheat growing without cell division.Amer. Jour. Bot. 48(6): 438–446. Illus. 1961.—A morphological and histological study has been made of wheat seedlings growing without desoxyribonucleic acid (DNA) synthesis, mitosis, and cell division after gamma‐irradiation of the grain. The development of these seedlings parallels the normal development of unirradiated wheat in correlative growth of primordia and organs and in the production of highly differentiated cell and tissue types (e.g., trichoblasts, vascular elements, chlorenchymatous mesophyll, and cortical parenchyma). The absence of cell division makes these seedlings differ from unirradiated plants in several respects: no initiation of new organs; abnormal maturation of regions corresponding to the meristems; greater cell lengths. Guard cells, subsidiaries, and hair‐bearing cells are lacking, except in the apical 2–3 millimeters of the first leaf. Anatomic similarities of these plants to those treated with maleic hydrazide, including maturation to the tip of the roots, are discussed. The central cylinder of the upper pair of lateral seminal root primordia becomes highly differentiated with negligible elongation of the primordia. The occurrence of a high degree of differentiation after doses of radiation that produce extensive chromosome breakage indicates that in the absence of mitosis the chromosomes need not remain intact for the cells to continue differentiation. These studies show that such seedlings can be used to indicate the capacities of the cells in the embryo for differentiation without DNA synthesis, mitosis, and cell division.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11665.x

出版商:Wiley    

年代:1961

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11666.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Rediske, J. H., and K. R. Shea. (Weyerhaeuser Co., Forestry Research Center, Centralia, Wash.)The production and translocation of photosynthate in dwarfmistletoe and lodgepole pine.Amer. Jour. Bot. 48(6): 447–452. Illus. 1961.—A study was made, using C14O2, of the host‐parasite relationship of dwarfmistletoe (Arceuthobium americanumNutt.) growing on lodgepole pine (Pinus contortaDougl.) seedlings. The translocation patterns of radioactive photosynthate were outlined to determine the feasibility of using a systemic selective herbicide for dwarfmistletoe control. Selective administration of the C14O2for 24‐hr experimental periods in a controlled‐environment chamber demonstrated that dwarfmistletoe carried on photosynthesis and that a significant portion of the photosynthate (largely sucrose) was translocated into the pine. Photosynthate produced in a terminal needle cluster of the pine was translocated basipetally to the roots, but also was accumulated in intercepting dwarfmistletoe plants. Both glucose and fructose as well as sucrose were found in large amounts in pine‐produced photosynthate, but primarily sucrose was translocated, as demonstrated by paper chromatography. The principal damaging effect of the dwarfmistletoe appeared to be the cutting off of photosynthate translocation to the roots. The dwarfmistletoe acts as a biological girdle resulting in an accumulation of photosynthate above the site of infection. Presumably carbohydrates can be withheld from the roots in quantities sufficient to cause the characteristic decline of the tree that is associated with severe attack by dwarfmistletoe.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11667.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Batra, LekhR. (U. Kansas, Lawrence), and HeleneFrancke‐Grosmann.Contributions to our knowledge of ambrosia fungi. I. Ascoidea hylecoeti sp. nov. (Ascomycetes).Amer. Jour. Bot. 48(6): 453–456. Illus. 1961.—The genusAscoideaBref.&LindauinBrefeld (1891) belongs to the family Ascoideaceae (Endomycetales, Hemiascomycetidae).Ascoideadiffers from all other ascomycetes by its possession of characteristic multispored asci which proliferate, the newer asci being formed through the collar‐like wall remnants of older asci. Ascogenous hyphae are absent. The present fungus differs in many ways from the type and the only species of the genus,A. rubescensBref.&Lindau.Ascoideahylecoeti reproduces asexually by chlamydospores. The asci are conical and many spored. They are aggregated in thick clusters of 50–200 individual asci. The number of ascospores per ascus is much larger than that ofA. rubescensand their size is much smaller.Ascoidea hylecoetiis known to occur only in association with the genusHylecoetus, one of the ambrosia beetles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11668.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Brewbaker, JamesL. (Brookhaven National Laboratory, Upton, New York), and SanatK. Majumder.Cultural studies of the pollen population effect and the self‐incompatibility inhibition.Amer. Jour. Bot. 48(6): 457–464. Illus. 1961.—A significant effect of decreasing population size on pollen germination in vitro was observed in 8 angiosperm genera. Reduction of pollen germination percentages (Y) occurred linearly inPetunia inflata, with decrease of population size (X) below 200 grains per 0.01–ml drop, and differences from linear regression of Y = 1.43 + 0.39X were not significant. Water extracts of pollen and other plant parts contained a factor or factors which could overcome fully the population effect. The pollen growth factor was dialyzable, insoluble in ether, relatively heat‐stable, and was not replaceable by kinetin or auxin. Cultural requirements of petunia pollen were studied in detail and linear growth rates in vitro of 122 μ/hr and in situ of 900 μ/hr were recorded. Growth in hanging drops tapered off in ca. 6 hr, at about the time of second mitosis. Pollen tube inhibition by incompatibility (S) alleles in situ also was observed after about 6 hr. The inhibition of pollen‐tube growth by stylar extracts was investigated by in‐vitro matings of 6 S allele genotypes. Highly significant differences in 5 hr growth were observed in a study of 4200 tubes; incompatible matings averaged 342 μ, semi‐compatible (e.g., S11× S1S2) averaged 434 μ, and compatible averaged 516 μ. In semi‐vitro studies of stylar segments which were pollinated and placed on agar, incompatibility was consistently and clearly evident. It is proposed that the pollen growth factor or factors (“PGF”) may be consumed during growth and that incompatibility inhibits the production or utilization by, or transfer to the pollen tube of PGF. Assuming that second mitosis involves extraordinary demands for PGF, the differences between bi‐nucleate and tri‐nucleate pollen grains in vitro and in incompatibile matings thus might be satisfactorily resolved.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11669.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Steinhart, C. E., L. C. Standifer, Jr., and F. Skoog. (U. Wisconsin, Madison.)Nutrient requirements for in‐vitro growth of spruce tissue.Amer. Jour. Bot. 48(6): 465–472. Illus. 1961.—Callus derived from seedlings of Norway spruce has been cultured for 3½ yr on a medium supplemented with malt extract. The responses of the callus to auxin, kinetin, light intensity, and pH were determined. The malt extract employed was fractionated by various methods, and it was shown that the active fractions were generally ninhydrin positive. The free amino acid composition of the extract was determined. Malt extract could be replaced completely by casein hydrolysate. Arginine, glutamine, or urea, although less effective, also supported continuous growth of the callus. In contrast, NH4NO3as a sole source of nitrogen failed to support growth. The same compounds that supported growth of the established strain of callus also stimulated initial formation of callus from seedlings. Inositol was the only vitamin that could be shown to stimulate callus growth. A synthetic medium has been developed for the cultures; it includes inorganic nutrients, naphthaleneacetic acid, kinetin, myo‐inositol, and either arginine or urea. Thiamin, choline chloride, and cystein are also added to the medium, although a requirement for the latter 2 of these 3 compounds has not been demonstrated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11670.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Hueber, FrancisM., and JamesD. Grierson. (Cornell U., Ithaca, New York.)On the occurrence of Psilophyton princeps in the early Upper Devonian of New York.Amer. Jour. Bot. 48(6): 473–479. Illus. 1961.—Although several critical studies ofPsilophyton princepshave limited its range to Lower and Middle Devonian, the writers have been able to identify plant remains from the Upper Devonian asP. princeps.Specimens prepared by maceration and transfer techniques demonstrate positive agreement of characteristics of the spines, cuticle and vasculature withP. princepsfrom Canada and Scotland.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11671.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

Evert, RayF. (U. Wisconsin, Madison.)Some aspects of cambial development in Pyrus communis.Amer. Jour. Bot. 48(6): 479–488. Illus. 1961.—The vascular cambium of pear is continually undergoing changes in composition and dimension. Circumferential growth occurs through oblique, anticlinal divisions of fusiform initials, followed by apical, intrusive growth. The production of new fusiform initials proceeds at rates which result in numbers of cells far in excess of those required for adequate circumferential expansion. Many of these cells are lost from the cambium, and others are transformed to ray initials. Consequently, a relatively low proportion of the new initials survive to repeat the cycle of elongation and division. New ray initials arise from existing ray initials and from fusiform initials. Although the immediate environment has a profound effect upon the fate of each cambial cell, over‐all cambial changes are obviously synchronized.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11672.x

出版商:Wiley    

年代:1961

数据来源: WILEY

摘要:

LaChance, LeoE. (Biology Dept., Brookhaven Nat. Lab., Upton, L. I., N. Y.)Studies on the effect of carbon dioxide on X ray‐induced chromosome aberrations in Tradescantia. II. Relation to dose rate and environment during irradiation.Amer. Jour. Bot. 48(6): 489–492. 1961.—The effect of carbon dioxide on radiation‐induced chromosome aberrations has been investigated to determine the relation of this agent to dose rate and the efficacy of a pretreatment followed by X‐irradiation in nitrogen or in vacuo. Carbon dioxide and air, present during the radiation treatment, significantly increase the frequency of chromosome aberrations induced by 300 r of X rays through a 46‐fold difference in dose rate. Pretreatment with CO2and air also increases the aberration frequency if the radiation occurs in air. Pretreatment is completely ineffective when the inflorescences are irradiated in vacuo or in nitrogen. Thus it appears that CO2acts synergistically with oxygen in increasing the frequency of chromosome aberrations induced by X rays.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1961.tb11673.x

出版商:Wiley    

年代:1961

数据来源: WILEY