Showing papers in "American Journal of Botany in 1944"

The influence of some respiratory inhibitors and intermediates on respiration and salt accumulation of excised barley roots

Abstract: THE ACCUMULATION of salts by barley roots is dependent on a concomitant aerobic respiration. This has been demonstrated by the use of reduced oxygen concentrations (Hoagland and Broyer, 1936). A logical next step, as suggested by Hoagland and Broyer (1942), is an attempt to analyze the nature of the linkage between salt accumulation and respiration through the use of respiratory inhibitors. This report consists of a preliminary survey of the effects of the oxidase inhibitors, cyanide and azide, and of the dehydrogenase inhibitors, iodoacetate and malonate, on the respiration and the accumulation of the bromide ion by excised barley roots. When the latter two reagents were found to be strong inhibitors of both processes concerned, the problem was extended to include the effects of malic, succinic, fumaric, and citric acids, since these compounds are considered to be both intermediates and catalysts in a cycle whereby pyruvate is oxidized (Elliott, 1941; Evans, 1941; Barron, 1943; Krebs, 1943; and references listed). The experimental data are preceded by a detailed discussion of the method of growth and preparation of barley roots as well as those characteristics of the roots which have a bearing on subsequent experiments. GROWTH AND PREPARATION OF THE BARLEY ROOTS FOR STUDY BY MICROSPIROMETER METHODS.-Growing the plants.-Prevot and Steward (1936) and Ulrich ( 1941 ) demonstrated that under certain conditions barley produces long, unbranched roots with a high capacity for absorbing and accumulating salts. By combining and modifying their methods, unbranched roots, 12-15 cm. long, relatively free of root hairs, and of a uniform diameter slightly under 0.5 mm. were grown in five days. The grain used was the "Sacramento" strain of barley from the 1939 crop grown at Davis, California. Approximately twice as many grains as plants to be needed are soaked for twenty-four hours in a cheesecloth sack suspended in well-aerated distilled water inside a thoroughly darkened, circulating air type incubator at 240 ? 0.050C. The air, before passing through the water, is brought to the proper temperature by passing it through a series of copper coils within the incubator. After washing the soaked grains with distilled water, twenty of those with

Translocation of radiophosphorus in the phloem of the cotton plant

Abstract: THE SUBJECT of phloem transport has been quite adequately reviewed in recent years. Curtis (1935), Mason and Phillis (1937) and Crafts (1938) have summarized existing data and hypotheses, each from his respective point of view. The opinions expressed by the many workers in this field are diverse both as to tissues involved and forces responsible for movement. Hence, it is anticipated that further reviews will contribute less than presentation of experimental results. EXPERIMENTAL.-Since the problem of phloem transport is an old one, many different experimental methods have been employed in its attempted solution. The present study utilizes the advantages gained by the use of tracer elements and presents data which heretofore have not been available by means of the application of older methods. This method is characterized by extreme convenience in manipulation, and it allows detection of extremely minute quantities of migratory material. It is rapid, direct and precise to about seven per cent under the conditions of these experiments. The object of the study is to follow the translocation of phosphorus from the leaf to other parts of the plant. It is known to accumulate in the leaves following delivery there by the transpiration stream (Biddulph, 1940). In order to demonstrate its redistribution, an "injection technique" was employed to localize an amount of radiophosphorus in the leaf to be studied; then the radiophosphorus was followed to other parts of the plant by means of its radioactivity. The path of its movement can be adequately traced by means of the presence of the radioactive material in the tissues traversed. The investigation consists of two parts, as follows: first, experiments were conducted in order to learn how closely the migratory phosphate follows the vascular traces of the petiole while moving from the leaf into the stem; second, experiments were conducted in order to learn whether the radiophosphorus, after leaving the leaf, moved through the xylem or the phloem of the stem. Both parts yielded evidence on the direction of movement in the stem. Vascular anatomy and translocation.-Cotton seed (Gossypium sp.), obtained from the Agronomy Department of the Alabama Experiment Station, was delinted by immersion in concentrated sulfuric acid for three minutes, washed free from acid and dried. The seeds were then dusted with Semesan and placed in moist paper toweling (Scott Tissue Towels No. 5a, Folded) to germinate, after which they were transferred to sand culture or to solution culture.

A karyosystematic study of the genus agave

Abstract: THE PRESENT investigation of the karyotypes of the genus Agave has had several objectives in view. The widespread distribution of some 300 species, the fact that the plants require from fifteen to twenty years to mature and that they hybridize very easily, make the taxonomic and phylogenetic study of the genus extremely complicated and very difficult to attack. It was hoped that chromosome studies of the individual species might throw some light on the present state of confusion in the classification of the genus and on our knowledge of its evolution. An understanding of the distribution of the karyotype of this group of plants may aid in the clarification of generic relationships. The "Yucca-Agave" karyotype consists of a pattern of ten large chromosomes on the periphery of the metaphase plate and fifty small ones differing slightly in size grouped in the center. This karyotype is also found in Yucca, Furcraea and Hosta. Several workers have suggested that a karyotype so unique in the plant kingdom must be of significance and have proposed using it as a basis for the revision of several related genera of the Liliaceae and Amaryllidaceae. Watkins (1936) objected to this suggestion, one of his reasons being that in the large genus Agave only four counts had been reported, those not in agreement. The data presented in this paper together with those of recent workers overcome this objection. The occurrence of polyploidy in Agave raises the question as to whether the correlations between polyploidy and vegetative structure common in other genera are also to be found in Agave and whether the higher polyploids are more useful, as is generally true in plant genera of economic importance. It is also interesting to note whether any correlation can be made between polyploidy and geographical distribution and whether polyploidy is more predominant in one or another section of the genus. REVIEW OF LITERATURE.-Much work has been done on the genera containing the "Yucca-Agave" karyotype. This unique chromosome complex was early noted by Strasburger (1882), who described the diversity in length of chromosomes in Funkia (Hosta). The early workers, among them Strasburger (1900) on Funkia, Koernicke (1901) on Yucca, Schaffner (1909) on Agave, Muller (1910) 1 Received for publication February 14, 1944. Paper No. 736 from the Department of Botany and the Botanical Garden of the University of Michigan. This material was taken from a dissertation submitted for the degree of Doctor of Philosophy in 1938. Photographs of all the plants used, a detailed summary of the literature on the cytology of Agave, and various cytological methods tested may be found in the dissertation filed in the University of Michigan Library. The writer wishes to express her gratitude to Prof. W. R. Taylor under whom this work was pursued, for his kind suggestions and criticism. The writer also wishes to express her appreciation to Prof. H. H. Bartlett for the material which made this study possible and for his continued interest in this work. on Yucca, and Woycicki ( 1911 ) on Yucca, were concerned mainly with the number and size differences of the chromosomes and the fact that the large chromosomes show a definite tendency to pair in the somatic nuclei. The description by Muller (1912) of the chromosome complex of Agave americana, having twenty instead of ten large chromosomes arranged around the periphery of the metaphase plate, gave the first suggestion of a polyploid series in Agave. From about 1925 on, workers paid more attention to chromosome morphology and to the phylogenetic relationships that might be indicated from karyotype similarities. In the work of Taylor (1925) and Morinaga et al. (1929) on Yucca filamentosa; Imai and Kanna (1934), Akemine (1935) and Yasui (1935) on Hosta; Matsuura and Suto (1935) on Hosta and Yucca; Sato (1935), Doughty (1936) and Vignoli (1936, 1937) on Agave, relative size differences were brought out and terminal spindle fiber attachments indicated in the large chromosomes. A number of workers, including Koernicke (1901), Miyake (1905), Muller (1912), have stressed the similarities between the karyotypes of Funkia, Beschorneria, Yucca and Agave. Heitz (1926) was the first to suggest a correlation between taxonomy and cytology in the Agavoideae. More recently the papers of McKelvey and Sax (1933), Whitaker (1934) and Sato (1935) have pointed out the significance of the "Yucca-Agave" karyotype in classification and have also tried to find the ancestors of the "Yucca-Agave" group by studies of the karyotypes of the more primitive monocotyledons. A survey of the literature to date (table 3) indicates that the basic chromosome number of the genera Agave, Yucca and their allies is thirty and that the various karyotypes are identical or very similar in general morphology. MATERIAL AND METHODS.-The material for this study came from plants growing in the University of Michigan Botanical Garden. These plants cover a large portion of the normal distribution range of the genus and contain representatives of the most important groups of the genus except those of the West Indies. Many of the collections were made on a number of botanical expeditions conducted or sponsored by Professor H. H. Bartlett. Some of the plants were collected by Professor Bartlett in the Maya region of Yucatan, others by Dr. C. L. Lundell and A. Whiting in Central Mexico, by H. S. Gentry in Mexico and by 0. Grassl in New Mexico. The largest number of representatives from the United States were collected by Dr. E. U. Clover in Texas. The remainder of the assortment is derived from miscellaneous sources, such as gifts from individuals or seeds from other botanical gardens and from the U. S. Department of Agriculture. Unfor-

Factors affecting the growth of datura embryos in vitro

Abstract: IN EARLIER papers (van Overbeek, Conklin and Blakeslee, 1941, 1942) it was reported that Datura embryos, wheni isolated at the "heart-shaped" stage, require for growth the addition to the medium of some factor present in coconut milk. Later (van Overbeek, 1942) embryos isolated at the proembryo stage were also successfully cultivated in vitro by using fractionation products of coconut milk. The substance (or substances) responsible for the activity of coconut milk on the growth of embryos was called embryo factor (van Overbeek, 1942). Soon after it was found that coconut milk contained substances essential for the growth of embryos in vitro, investigations were started for the purpose of identifying the chemical composition of the embryo factor. In the course of this work, in which the growth of the embryos was used as a measure of embryo factor activitv, it became necessary to know more precisely the conditions which affect the growth of the embryos. The following points were investigated: (a) effect of temperature, (b) effect of pH, (c) effect of sucrose, (d) embryo factor activity of pure substances and extracts, (e) inhibitory substances, and (f) fractionation of coconut milk for embryo factor.

Specialization of vessels within the xylem of each organ in the monocotyledoneae

Abstract: IN PREVIOUS papers on the vessels of the Monocotyledoneae, the present author discussed the occurrence of vessels (1942), their origin and certain general trends of specialization (1943a), and their specialization in the late metaxylem of various organs (1943b). The primary object of the present report is to determine the course of specialization of vessels throughout the metaxylem within each organ of the plant. Insofar as possible, the protoxylem will receive similar consideration. As a secondary object, specialization of the early metaxylem from organ to organ will be compared with similar changes in the late metaxylem from organ to organ. The previous paper (1943b) which concerned such changes considered only the larger vessels in the late metaxylem. This secondary object should indicate whether or not the rate of specialization throughout the metaxylem has been the same in all organs. As pointed out in the previous papers of this series, there are few references in the literature which are pertinent in this discussion of vessels in the Monocotyledoneae. MATERIALS AND METHODS.-Materials from all available organs of 306 species in 204 genera among 34 families, as defined by Hutchinson (1934), were used in this study.2 The number of genera and species in each family is about the same as given in the latest paper in this series (1943b), and merely the families are presented here to indicate the scope of the investigation: Agavaceae, Alismataceae, Alstroenmeriaceae, Amaryllidaceae, Araceae, Bromeliaceae, Butomaceae, Cannaceae, Commelinaceae, Cyperaceae, Dioscoreaceae, Eriocaulaceae, Gramineae, Haemodoraceae, Hypoxidaceae, Iridaceae, Juncaceae, Liliaceae, Marantaceae, Musaceae, Orchidaceae, Palmae, Pandanaceae, Pontederiaceae, Potamogetonaceae, Ruscaceae, Scheuchzeriaceae, Smilacaceae, Sparganiaceae, Strelitziaceae, Trilliaceae, Typhaceae, Xyridaceae, Zingiberaceae. It should be pointed out that the number of genera and species in the highly specialized grasses is relatively high. Consequently, this family will be treated both separately and together with the remainder of the families. Using methods previously described (Cheadle, 1942), all materials were macerated and most of them sectioned as well. The macerations were often of greater use than the sections, although the latter were valuable in confirming positional relationships of the various elements of the meta1 Received for publication October 7, 1943. With the support of a grant from the American Philosophical Society, and two grants from the American Academy of Arts and Sciences. 2The author is grateful to all those who have had a share in the accumulation of data for this paper. He also expresses appreciation to the Biological Laboratories of Harvard University for the use of photomicrographic equipment. xylem. Incomplete macerations were also of similar value. OBSERVATIONS AND DISCUSSION.-Because only primary xylem is treated in this paper, it will be necessary to use both the terms protoxylem and metaxylem. These terms, as pointed out by Esau (1943), have been variously defined, most recently in a fashion that stresses features revealed in on5ogenetic development. In a report which is phylogenetic in nature, it is perhaps necessary merely to make clear what structures are meant by the terms which are being used in presenting the data and conclusions. It is unnecessary in this particular paper, for example, to report what exact type of element first appears ontogenetically in each organ. There seems to be no doubt that when a wide variety of conducting elements occurs in the primary xylem, those elements having annular wall thickenings mature first, those having spiral thickenings mature next, and those having typical bordered pits mature last. However, because of various intergradations there is no absolutely clear boundary between any two of the above elements. Furthermore, the conducting elements in the primary xylem of some fleshy representatives are not often easily identifiable from the standpoint of the presence or absence of pitting, especially in the shoot system. With regard to papers of this particular nature, it is perhaps fortunate that few of these fleshy plants have vessels. Only a small number of such plants are, therefore, involved in the present discussion. The use of the term protoxylem will be such as to involve those elements with either annular or spiral thickenings or both. All other elements will be considered as metaxylem. The earliest metaxylem will then normally consist of the intermediate forms such as those with reticulate sculpturing on the side walls. In some cases, the late metaxylem may consist of these so-called intermediate forms. When the actual meanings of the terms late and early metaxylem are given later, however, it will be seen that these unusual cases will not confuse the issues in this paper. The terms vessel, vessel member, scalariform and porous (simple) perforation plates, and tracheids will be used as defined by the Committee on Nomenclature of the International Association of Wood Anatomists (1933). The more convenient term vessel will be used instead of vessel member wherever possible and where its use will not be confusing. Little difficulty was encountered in choosing a method for arbitrarily dividing the metaxylem of most roots for the purposes of comparison. This was especially true in such large roots as those of the palms (fig. 1) and aroids, where the xylem strands extend for a considerable radial length. Certain of the smaller roots (fig. 3) were more troublesome in this regard, because of the smaller number of elements

Studies in the morphology of the cyperaceae. ii. the prophyll

Abstract: TAXONOMIC AND morphological literature contains frequent mention of "prophylls" ("Vorbliitter," "prefeuilles"). During the author's study of the Cyperaceae, it became increasingly evident that general usage of the term is confusing and far from uniform. In attempts to locate a reasonable definition of the term, it was found that most "definitions" are either too indefinite or too restricted. For example, Jackson (1900), Rendle (1904), Strasburger and Benecke (1913), Wettstein (1917), Engler (1926), Artschwager (1930), and others use "prophyll" as the equivalent of bracteole, either on floret axes or inflorescence branches. Occasional restriction is to the lower one or two bracteoles. On the other hand, Turpin (1819), the Bravaises (1837), Pax (1890), Arber (1925), Goebel (1933), and others state that reduced leaves called "prophylls"occur at the base of both vegetative and flowering branches. Usually there are two in dicotyledons and one "addorsed" prophyll in monocotyledons. In several papers, exceptions are cited; in others the usage of the author, following the introductory statement, is frequently variable. Since the bases for studying and denoting '"prophylls" in the inflorescences of the Cyperaceae are most unsatisfactory, an extensive search in the literature was undertaken to determine if "prophylls" are morphological entities which are of value in developing concepts of inflorescence reduction. More than one hundred and fifty papers were examined, but, since many are both repetitive and contradictory, it is unnecessary to cite all. It is, however, of importance to review the theories, evidences and assumptions on which most of the confusion rests. This review will then serve the general function of showing what "prophylls" may be as well as the special function of a preface to publication concerning the cyperaceous inflorescences where the term cannot be applied with morphological significance.2 ORIGIN OF THE TERM PROPHYLL."-Probably the first anid the most persistent idea affecting the several theories of "prophyll" structure is the apparent drive to find homologies between dicotyledons and monocotyledons. The contrast of two cotyledons and two "prophylls" with one cotyledon and one "'prophyll" has naturally led to the seizure of slight evidences and "abnormalities" to demonstrate the derivation of the monocotyledons from the dicotyledons. Frequent occurrence of two veins, two teeth, a tendency to split, two keels and the so-called "ab-

Evidence for natural hybridity between guayule (parthenium argentatum) and mariola (parthenium incanum)

Abstract: THE ACCELERATED investigations of Guayule (Par-thenium argentatum) in an attempt to mold it into a stable crop plant have quickly revealed a number of complicated problems for the plant breeder. Some of these would be encountered in working similarly with almost any wild plant species, while others are seemingly peculiar to Guayule. The resolution of many of the problems of the latter category in particular is dependent upon a thorough knowledge of the species itself. This is equally true whether certain improvements of the present commercial strains of Guayule are involved or entirely new strains are to be created. Therefore, a demonstration that Guayule hybridizes naturally with Mariola (Parthenium incanum) is of considerable value because it suggests that the present nature of Guayule as a species is due, in part at least, to the operation of this phenomenon during its past history. Too little is known of the actual genetic nature of Guayule to be specific on many points. The present report should be regarded as being only of a preliminary nature insofar as many of the items mentioned are concerned. Throughout a large proportion of the natural range of Guayule, the closely related species, Mariola, is coexistent. The two species intermingle freely and there is ample opportunity for cross pollination. However, natural hybridization between them has not been shown previously. McCallum (1941) suggested, without stating the evidence or describing the hybrids, that certain of his plants were the result of crosses between Guayule and Mariola. Botschanzewa (1933) succeeded in obtaining a small number of hybrids from artificial crosses between these species and concluded that a portion of the diversity encountered in Guayule is the result of hybridization. From a study of our material, it is possible to show with some certainty that Guayule and AMariola are hybridizing in the wild and to presume with some justification that, phylogenetically, such crossing has contributed materially to the nature of both species. MATERIAL AND METHODS.-A large quantity of Guayule seeds and a small collection of Mariola seeds were gathered in the states of Durango, Nuevo Le6n, San Luis Potosi, and Zacatecas, Mexico, by Dr. LeRoy Powers and in the Trans-Pecos area of western Texas by Dr. Powers and Mr. Walter Federer. Seeds were taken from individual plants, massed from selected plants and bulked from randomly encountered non-selected plants. Each type of seed collected was kept separate for each locality from which it was obtained. From these seed sources, over 205,000 plants of Guayule and nearly a thousand of Mariola are being grown. This mass of material, first in the greenhouse and subsequently in 1 Received for publication October 22, 1943. the field has formed the basis for the present study. A microscopic study of the trichomes of Guayule and Mariola revealed that these structures are radically different in the two species. If interspecific hybrids were present among the plants being cultured, then the trichomes should give some indication of the influence of both species. For this reason, the total greenhouse population was examined in the seedling stage for possible hybrids. The indument of each plant was critically observed with the aid of a hand lens to determine whether the disposition of the trichomes conformed to the usual pattern found in Guayule or whether significant deviations were present. Also, divergences from the predominant type of trichome on the leaf surfaces of ordinary Guayule were carefully noted. SOURCES OF THE PUTATIVE HYBRIDS.-From the total greenhouse population, 163 individuals, or slightly less than one-tenth of one per cent, were tentatively identified in the seedling stage as being interspecific hybrids because of the type of trichomes present. Additional morphological evidence supporting these selections was obtained as the plants developed, as will be shown below. Thirty-four of the hybrids are the progeny of 22 individual plants, while the other 129 came from plants where the seeds had been massed or bulked. Seeds yielding these hybrids were obtained from widely separated locations in Texas and Mexico. The largest number from a single seed collection came from a locality about thirty miles west of Catorce in Zacatecas, Mexico, but a number of hybrid seeds were obtained in the state of Durango. In Texas, seeds giving hybrid plants were gathered from points in the general areas around Fort Stockton, Balmorhea, Alpine, Shafter, Plata, and Tesnus, as well as from a number of places completely isolated from any town. Hybrids have been found in cultures of the usual type Guayule, the miorotrichome type2 and the "intermediate type" showing that crossing is not restricted to a limited portion of the species. It is notable that one hybrid plant came from a massed collection of Mariola seeds. In all respects, this plant very closely simulates the other hybrids. In addition to the hybrids noted above, 25 out of 28 members of the progeny of a single plant identified in the field as Mariola by Powers and Federer appear similar in varying degrees to the hybrids. The other three members look like Mariola. There is a certain amount of segregation apparent among these plants, but this cannot be followed profitably because of the lack of specific information about the parents. Evidently the plant from which the seeds were obtained was itself a hybrid, since the

The geometry of growth and cell division in columnar parenchyma

Abstract: THE LAWS of growth and cell division in epithelial mosaics, considered as covering plane surfaces, have been discussed in an earlier paper (Lewis, 1943b). In extending that study to parenchymal cells in their three dimensions, the previous publication may be considered as Part I, and familiarity with its simple conclusions will be assumed. It was proposed to regard the plant body as a cylindrical shaft (root and stem in continuity), with rounded ends at the root tip and apical growing point respectively. The plant so constituted is a polyhedron with a countless number of facets, each of which is bounded by a polygonal cell-outline on the free surface. This massive polyhedron is composed of microscopic polyhedra (the cells), and the polygonal surface pattern of each of them obeys precisely the same law that governs the surface pattern of the entire plant. In a plane surface, the sum of the angles at any vertex, where the cellular polygons meet, must be the 3600 of the circle; and the same is true of the angles formed by lines drawn from the corners of any polygon to meet at a vertex within its interior. In three dimensions, as in a mass of parenchymal polyhedra, the sum of the solid angles meeting at any vertex must be 4 7r, the surface of a sphere (of any radius, considered as a unit); and the sum of the solid angles formed by projecting the edges of the surface polygons of a single polyhedron to a vertex in its interior must also be 4 7r. The ordinary number of sides which meet at a vertex in the plane mosaic is three, and hence the average shape of epidermal and epithelial cells on surface view is hexagonal. The smallest and the ordinary number of cells to meet at a vertex in a space-filling mass of polyhedra is four, which is consistent with an average of fourteen facets per cell. The necessity that the sum of the solid angles formed by projecting the edges of a polyhedron inward to meet at a central point shall equal 4 7r, is apparently the explanation of Euler's theorem, to which the polygonal surface pattern of every polyhedral cell must conform.2 Under these geometrical requirements parenchymal cells grow and divide according to a definite plan,

The cytogenetics of hybrids in bromus. i. hybrids within the section ceratochloa

Abstract: ONE OF the commonest, most widespread, and variable groups of grass species in western North America is the subgenus Ceratochloa of the genus Bromus, of which the best known species native to the United States are B. carinatus H. & A. and B. marginatus Nees. The problem of the number of species actually present in this group has been a constant puzzle to systematists, as is evident from the discussion of Hitchcock (1935, p. 38). In this manual he recognizes four native species of Ceratochloa, but the list of synonyms under the various species names (op. cit., pp. 811-817) indicates that fourteen different species have been described by various authors. Cytologically, the great bulk of the forms are octoploids, with 2n 56 (Stebbins and Love, 1941), but hexaploid (2n = 42) and decaploid (2n 70) counts have been recorded (Stiihlin, 1929; Nielsen and Humphrey, 1937; Nielsen, 1939), while there is one doubtful record of a diploid form (Stiihlin, 1929). In an attempt to secure this purported diploid, the senior author obtained seed of B. carinatus from Stiihlin's source, the Munich Botanical Garden, but the strain received was a typical octoploid. In view of the evidence presented below as to the probable origin of the B. carinatus complex, the presence of a diploid in this complex seems highly unlikely. In addition to its interest from the systematic standpoint, this complex contains forms of considerable forage value (Hitchcock, 1935, p. 33; Sampson and Chase, 1927, pp. 21-22). B. marginatus has been recommended by Stewart, Walker, and Price (1939) for reseeding range lands of the intermountain region. Among a large series of grass species sown in experimental range plots throughout California, B. carinatus has proved, one of the most readily established of any species native to the state (Burle Jones, unpublished data). Therefore, hybrids between different forms of this complex might be of value both as an aid to understanding the species problem as it relates to this group, and as a source of new varieties for establishment on range lands. For the latter purpose another series of hybrids was considered promising-between the B. carinatus complex and an eVen more valuable forage grass belonging to the section Ceratochloa, the South American B. catharticus Vahl. (= B. unioloides HBK, cf. Hitchcock, 1935). The work reported in the present paper, however, has shown that these latter hybrids are of more interest from the phylogenetic and systematic than from the agronomic point of view. MATERIAL AND METHODS.-The strains used in the present hybridization experiments are part of a large collection assembled by the senior author and