Showing papers in "American Journal of Botany in 1930"

Primary dormancy, after-ripening, and the development of secondary dormancy in embryos of ambrosia trifida

Abstract: The fruits of Ambrosia trifida are dormant at maturity. The dormancy is in the embryo since germination does not take place even when the embryos are freed from all enveloping structures. An after-ripening process must precede germination, but even when the seeds are after-ripened their germination, especially at high temperatures, may be considerably delayed or prevented altogether due to the fruit and seed coats. Failing to germinate under such conditions the embryos develop a second dormant condition more pronounced than the initial or primary dormancy. Since after-ripening, germination, the development of secondary dormancy, and possibly the primary dormancy of the embryo during its period of growth and maturity on the plant are more or less influenced by these membranes, a brief description of the embryo with its accompanying structures will be given at this place.

The chromosomes of some dioecious angiosperms

Abstract: The cytological investigations reported in the present paper were undertaken with the purpose of determining the exact circumstances of chromosome distribution in the division of the pollen-mother-cell nuclei of certain dioecious angiosperms. Attention has been focused on the stages of the heterotypic division in which the "homologous" chromosomes pair and separate, in order to detect any morphological difference between members of a pair that might be correlated with the usually dioecious condition of these species. No good evidence of such a difference has been found in Bryonia dioica L., Clematis virginiana L., Smilax herbacea L., Menispermum canadense L., or Carica papaya L., while the conspicuous heterochromosome pair of Lychnis cdlba Mill. (Melandrium album L.), already described by investigators in England, Sweden, and Germany, has been identified in material collected in the neighborhood of Madison, Wisconsin. A preliminary report has already been made of some of the results of the present work (Lindsay, 1929).

The morphology and anatomy of the achene

Abstract: The majority of botanists have long since agreed that the achene has been derived from the follicle by reduction. However, supporters of the opposing view, namely, that the multiovular structure (follicle) has been derived from the uniovular (achene) are not lacking (4). The present investigation has been undertaken to look for proof of this supposed reduction and to determine the morphological and anatomical changes which have occurred. Both the morphological and the anatomical evidence support the view that the achene is a reduced follicle. The morphological changes are a marked decrease in the size of the carpel and in the number of ovules per carpel, the multiovular carpel becoming uniovular. The anatomical changes involve the reduction of the vascular tissue both in the number of traces which a carpel receives and in the traces themselves within the carpel. The Ranunculaceae and the Rosaceae were chosen as most suited to this study, since they provide genera with a considerable variety of follicle and achene types. A follicle is " the fruit of a single carpel dehiscent by one (the ventral) suture." It contains from few to many seeds attached along its two margins. The typical carpel (or follicle), being a modified leaf, receives the vascular supply of a typical angiosperm leaf, namely three bundles: the median of these is the dorsal trace and plays no part in the ovular supply; the other two, variously known as "marginal" or "ventral traces " (6), give off a branch to each ovule attached to the margins along which they run. Branches from all three bundles may or may not be given off to the ovary wall. The follicle has, therefore, an abundant supply of vascular tissue. An achene is a "small, dry, indehiscent, one-seeded, seed-like fruit or carpel in which the covering does not adhere to the seed, as in the sunflower or buttercup." Unlike the follicle, the achene does not receive a typical supply of vascular tissue. It has usually only a single trace. The many-seeded condition, such as is found in the follicle, is commonly [The Journal for July (I7: 627-702) was issued August 6, 1930.] 46 703

Oxygen requirements for root growth of cuttings in water

Abstract: Those who attempt to review the literature on aeration as affecting plant growth find it varied and voluminous. Many reports are conflicting as might be expected in so large a field. Some phases of the subject, such as oxygen requirement for growth in liquid media, have not been extensively investigated. The present paper shows some of the effects of known amounts of dissolved oxygen on growth of roots from cuttings. Livingston and Free (io), using sealed soil containers which could be auto-irrigated and aerated, concluded that plants vary in their requirements for oxygen, willow being a low and coleus a high oxygen type. Complete deprivation of oxygen caused sensitive species like coleus and heliotrope to wilt. The roots failed to take up water and the plants soon died. Cannon (3) in I9I5 noted a relationship between moisture, aeration, and temperature as environmental factors which control the distribution of plants. Free (8) found that buckwheat in culture solutions was not improved by aeration with air, oxygen, or nitrogen. It was not injured by nitrogen but was killed when aerated with carbon dioxid. Cannon (4) in 1925 showed that the requirements of cotton for oxygen varied with the temperature. Growth was normal at 21? C. when the air surrounding the roots had only 2.6 percent oxygen, while the plants in this same amount of oxygen but at 28? C. gave approximately one-fourth of normal growth. Corn at I8? C. or higher required more than Io percent oxygen in the air surrounding the roots. When the growth rate of plants was normal for a given concentration of oxygen, the addition of more of this gas did not further increase growth. Emerson (7) found the subterranean systems of plants growing on floating bog mats to be very superficial and nearly all above the water. He thought that some of this superficial development might have been due to toxic materials in bog water, but that oxygen doubtless played a part. Bergman (i) observed that roots of land plants do not live under prolonged submergence. The roots soon die and new ones are developed from the

Chromosome numbers in cultivated cucurbits

Abstract: The primary purpose of this investigation was to determine the chromosome number of the various species in the group of cultivated cucurbits with the idea in mind that a cytological study of the different members would serve as a valuable adjunct in a genetical analysis to be made later. The material does not lend itself easily to this type of study owing to the meagre amount of chromatin material and the correspondingly small and numerous chromosomes.

The development of dormancy in seeds of cocklebur (xanthium)

Abstract: In a previous paper (2) it was shown that dormancy may be induced in the after-ripened embryos of ragweed (Ambrosia trifida L) by means of high temperature germination in connection with restricted oxygen supply to the embryos due to the fruit and seed membranes that envelop them These embryos, however, were dormant at maturity and the induced secondary dormancy was evidently merely a reversal of the essential changes through which the embryos had gone in the after-ripening process or the removal of the original or primary dormancy The embryos of seeds of Xanlhium canadense and X commune have at no time during periods of dry storage of seeds in the burs exhibited any tendency to dormancy when placed under germinating conditions No doubt this is also true of other species of Xanthium Shull (4) compared the germination of embryos of seeds of X glabratum, when quite green, with those of fully ripened seeds and of seeds one year old and was able to detect no perceptible after-ripening in passing from the unripe to the ripe and year-old conditions The so-called dormancy or delay in the germination of these seeds at certain temperatures is due, as pointed out first by Crocker (i), to the restriction of the oxygen supply to the embryos by the seed coats for when the seed coats are removed and the naked embryos are placed under suitable conditions, germination usually takes place within 24 to 48 hours

Studies on the mycelium of psalliota campestris

Abstract: The configuration of cells and of their contents and of cell aggregates is the visible expression of the dynamic forces which control the development of the organism. Our knowledge of the structure and energy relations of cells is based largely on the interpretation of the visible form changes through which cells and their contents pass in their integration to form tissues and organs. Generally speaking, mycologists in the past have not devoted a great deal of attention to the processes controlling the form changes of fungous cells, though the fungi appear to offer a fruitful field for observation and experimentation along these lines.

Hastening the germination of some coniferous seeds

Abstract: Germination experiments on southern pine seeds (Pinus taeda, Pinus echinata, Pinus caribaea, and Pinus palustris) conducted in this laboratory in I928 (Barton, i) have been extended to include seeds of a number of different species of pine together with several other conifers. It seemed desirable to ascertain the response of these different forms to low temperature stratification which proved effective in hastening the germination of the southern pines. The present paper reports results of these tests on both I927 and I928 crops of seed. Of the I927 crop the seeds tested were: Pinus austriaca, Pinus Banksiana, Pinus Cembra, Pinus densflora, Pinus excelsa, Pinus flexilis, Pinus insignis, Pinus Laricio, Pinus Lambertiana, Pinus monticola, Pinus contorta Murrayana, Pinus ponderosa I, Pinus ponderosa II, Pinus resinosa, Pinus Strobus, and Pinus Thunbergii. All of these seeds except those of Pinus flexilis, were obtained from Thomas J. Lane, seedsman, and were received in this laboratory in July I928, when germination tests were started. They were collected in the fall of I927 and presumably were kept in dry storage at room temperature up to the time of shipment. Phe I928 crop of seeds included Abies arizonica, Cupressus macrocarpa, Libocedrus decurrens, Picea canadensis, Picea excelsa, Picea Omorika, Picea pungens, Picea sitchensis, Pinus austriaca, Pinus Banksiana, Pinus Cembra, Pinus contorta, Pinus contorta Murrayana I, Pinus contorta Murrayana II, Pinus contorta Murrayana III, Pinus Coulteri, Pinus densiflora, Pinus excelsa, Pinus flexilis, Pinus insignis, Pinus koraiensis I, Pinus koraiensis II, Pinus Lambertiana I, Pinus Lambertiana II, Pinus monticola, Pinus ponderosa, Pinus resinosa, Pinus rigida, Pinus Strobus, Pinus Thunbergii, Sciadopitys verticillata, Sequoia semperv'irens, Taxodium distichum, Thuya gigantea, Thuya occidentalis, and Thuya orientalis. Pinus contorta Murrayana I and Pinus flexilis (I927 and I928 crops) were furnished through the courtesy of the U. S. Dept. of Agriculture Forest Service, Rocky Mt. Experiment Station, Colorado Springs, Colo. All of the other I928 seeds were obtained from Thomas J. Lane, and most of them were received in this laboratory in November I928.

The endosperm of zea and coix

Abstract: The endosperm of the cereal grasses has been the subject of numerous investigations directed from many different points of view, but certain phases of its development, involving the differentiation of its tissues, the accumulation of food material, and the relations between the endosperm and the embryo, have not been thoroughly studied. The application of the principle of the alternation of generations to the higher plants during the latter part of the past century gave to the endosperm a new morphological meaning, which was modified and made more interesting by the discovery of "double fecundation" and by the studies on xenia at the very close of the century. In most studies of development, however, the embryo has been the structure emphasized, and the chief interest in the endosperm has been its r6le as a nurse tissue for the embryo. From the work that has been done on various grasses it is evident that there is considerable uniformity in the development of the endosperm. The polar nuclei remain in contact with each other, without fusing, until the time of fecundation. The union of a sperm with them has been observed in Zea (9, I2, I7) and in Triticum (ii), and all circumstantial evidences indicate that double fecundation regularly occurs in other species. After fecundation there is a period of rapid division of free nuclei, with a migration of nuclei toward the antipodal end of the endosperm cell (Randolph, I3). These nuclei are located in a thin wall layer of cytoplasm, and the center of the cell is a large vacuole (P1. XXVIII, fig. I3). The formation of cell walls apparently begins in the peripheral region, for a stage of development is soon to be seen in which the endosperm is a hollow mass of tissue surrounding a central cavity (text figs. I, 2). The steps of development preceding this stage have not been investigated in detail, but it is reasonable to assume that they are similar to those of corresponding stages in the development of the endosperm of typical angiosperms. It would probably be better to regard this hollow endosperm as a cellular mass having a large, multinucleate cell in the middle. This cavity is soon eliminated by further nuclear division and wall formation (text fig. 3 and P1. XXVIII, fig. I4). Of the course of development of the endosperm from this time onward we have only fragmentary information drawn from studies of different grasses. These studies long ago indicated considerable differentiation in the mature endosperm of the cereals. Publication 46 of the Waterman Institute, Indiana University. 37I

Local lesions on bean leaves inoculated with tobacco mosaic virus

Abstract: Necrotic lesions appear at the points of inoculation when tobacco mosaic virus is rubbed over the surfaces of leaves of a number of species of Nicotiana. Holmes (I) studied the development of such lesions in five different Nicotiana species. Lesions occurring on N. glutinosa make their appearance the second day after inoculation and are well developed on the fourth or fifth day. Since their number is largely determined by the concentration of virus in the inoculum, the lesions have been made the basis of a method for the rapid determination of virus concentration. The purpose of this paper is to describe briefly similar necrotic lesions which occur on the leaves of certain varieties of the common garden bean, Phaseolus vulgaris, when they are inoculated with the virus of tobacco mosaic, and to suggest a possible use of these lesions in measuring virus concentration. In securing virus for use as inoculum, care was taken to obtain samples that contained no virus other than that of tobacco mosaic. Samples of virus obtained from several different sources were used. All these samples resulted in the production of similar lesions on inoculated leaves of susceptible bean plants. The number of lesions produced on the leaves was roughly proportional to the concentration of virus used as inoculum. There was a multiplication of the virus in leaves on which local lesions developed. It is therefore believed that the disease described was caused by the virus of tobacco mosaic. METHOD

Comparative anatomy of the woods of the meliaceae

Abstract: A study of the correlation between the gross morphological and anatomical characters of certain families has as yet received little consideration. Systematic botanists have disregarded almost entirely the anatomical characters of the stem in their present schemes of classification. This may be due to the fact that wood samples are rather difficult to obtain and prepare for study, or to the general consensus of opinion that no correlation exists between morphological and anatomical characters. There is no doubt, however, that anatomical study will bring to light many important facts which will be of value to the systematic botanist in clearing up doubtful points. In the study of the comparative anatomy of the woods of the Juglandaceae by the author (9), for example, several facts of this sort were discovered, namely: (i) that the woods of Apocarya and Eucarya are easily separable; (2) that the woods of Juglans are divided into two distinct groups which correspond with the two groups separated by the structure of the nut; (3) that there is a difference in wood structure between the two sections Oreomitnnea and Pterilema of the genus Engelhardtia; and (4) that Alfaroa belongs with the Oreomunnea section of Engelhardtia. Similar examples could be cited from other families. In cases where investigators have been unable to find anatomical characters of taxonomic value they have usually either been working with groups which were more or less artificial and heterogeneous (like the Magnoliaceae in the earlier sense) or have endeavored to use for diagnostic purposes single isolated characters rather than a particular combination of characters. The present investigation was undertaken in an endeavor to throw light on the classification of the Meliaceae by a study of the comparative anatomy of the wood of its species, supplementing data from this source by facts from gross morphology. One hundred and twelve species of the family, representing 36 genera, were studied.

Species crosses in the genus cucurbita

Abstract: Of the ten species comprising the genus Cucurbita only three, C. Pepo L., C. maxima Duchesne, and C. moschata Duchesne are annual, and these are the only species cultivated in the United States. Obscurity has surrounded their origin and this has given rise to much discussion regarding their nativity. Some convincing evidence regarding the North American origin of C. Pepo has been furnished by Small (2I), who on collecting excursions to Lake Okeechobee, Florida, discovered a "gourd" growing on the southern shores of the lake, which he later found to be very similar to our present cultivated pumpkin. Small states that the foliage, flowers, and seeds of this wild pumpkin are indistinguishable from our economic forms of today, but that the fruit is much smaller, ranging in size from a baseball to that of a croquet ball. The color is pale yellow, and sometimes variegated with green markings. From a " memoir " of Hernando de Escalante Fontaneda, written in Spain about I575, Small quotes a description of what is no doubt the same general region in which his own excursions were made. One of the regions is designated by Hernando de Escalante Fontaneda as Tocola-a-chile, which when translated means "Gourd place bringing forth," or "Country where gourds are produced." Small (2I) believes that the wild pumpkin which he found near Lake Okeechobee is the same as the " gourd " mentioned in the old Spanish record of exploration in Florida, and that the Lake Okeechobee region, including the unexplored hammocks of Lake Istokpoga, to which this wild pumpkin is at present restricted, represents the original home of the pumpkin. Small (2I) also observes that the Seminole pumpkin, which pioneer white men found among the Seminole Indians in the region now known as Florida, still grown by the Seminole Indians of today, is a cultivated form of the wild type described above. "The stem and flowers are identical with those of our various cultivated pumpkins. The fruits are larger than in the wild plantand they vary from spheroidal, often much depressed, through pyriform to those with a short stout neck." It seems quite likely that the pumpkins found among Indian tribes by the early settlers, as well as among some tribes of the present day, have come up through the Seminole pumpkin from the original wild form of the Lake Okeechobee region. This wild pumpkin described by Small (2I) belongs to Cucurbita Pepo and may be considered the prototype of this species.

Enzym activities of juices from potatoes treated with chemicals that break the rest period

Abstract: When freshly-harvested potatoes are treated with chemicals such as ethylene chlorhydrin, sodium thiocyanate, and thiourea the rest period is broken, and sprouts begin to make their appearance uniformly throughout the lot, after about five to eight days. The untreated potatoes planted at the same time, however, usually do not show sprouts until several weeks later, and even then the sprouting is not uniform (4). It seemed desirable to study the enzym changes that take place in the potatoes during these few days in which the processes correlated with the breaking of dormancy are in progress, and to compare them with untreated tubers under the same conditions. This paper presents the results of a series of measurements of the enzym activities of juices obtained from potatoes which had been treated with chemicals but which had not yet sprouted. The three chemicals used for treating the potatoes were ethylene chlorhydrin (ClCH2CH20H), sodium thiocyanate (NaSCN), and thiourea (NH2CSNH2). These, although quite unlike in chemical character, produce similar results in the breaking of dormancy and therefore it seemed of special interest to compare them with regard to their effects upon enzym activity. The object of the experiment was to obtain partial or complete answers to such questions as the following: What enzyms show the greatest changes? How soon after treatment do the changes start? Do the different chemicals produce the same or different effects upon the enzyms? Is there any relation between the concentration of chemical used in treating the potato and the enzym activity of the press-juice? Is there any correlation between the sprouting response and the enzym changes? Are the chemicals acting directly upon the enzyms or do the chemicals act first upon the living matter and only indirectly upon the enzyms? Do the changes occur in the absence of the eyes or must these be present to permit a response? The enzyms mainly studied in this series of experiments were catalase,