Showing papers in "American Journal of Botany in 1970"

Determination of number and mitotic activity of shoot apical initial cells by analysis of mericlinal chimeras

Abstract: A B S T R A C T The dimensions of mericlinal sectors in periclinal chimeras resulting from replacement-displacement phenomena have been used to determine the number of shoot apical initial cells and their mitotic activity. Narrow sectors were always short, extending an average of less than three nodes. All long sectors were wide, involving 13 or 12 of the circumference of the stem. These observations define the origin of all primary growth as from 1-3 apical initial cells in each of the apical layers. The sectors reveal a surprising stability of cellular position at the center of growth, with a specific initial cell maintaining its position during formation of over 100 nodes. During vigorous vegetative growth of Ligustrum ovalifolium the initials themselves divide only about once in 12 days during the formation of three nodes. The mitotic index of the initials in privet shoot apices is 1.4, and this rate of division is sufficient for them to be the ultimate source

Origin and development of protein granules in maize endosperm

Abstract: Protein granule development in the starchy endosperm of normal maize (inbred line, W46A) was studied with optical and electron microscopy. The granules were first observed 12 days after pollination as spherical deposits, usually single, within an enclosing membrane. They developed from vesicles produced by the endoplasmic reticulum and were formed both as small localized cisternal dilations and as enlargements at the ends of endoplasmic reticulum. Dictyosomes also appear to proliferate protein granule vesicles. The protein accumulated in the granules appears to be synthesized outside the membranes. Once initiated, the granules rapidly increase in size and number as the kernel develops; their final diameter ranges up to 2 IA. Immature granules stain with a variety of biological dyes in aqueous solution as well as with metal stains; mature granules stain lightly or not at all. At kernel maturity, the protein granules are embedded in a protein

Crystal‐structure of ruthenium red and stereochemistry of its pectic stain

Abstract: A B S T R A C T A crystal-structure analysis of ruthenium red has indicated a composition of [Ru3Cls (OH)a (NH3)12 (H20)31. Each ruthenium ion is coordinated cubically with at least eight chloride ions, and it is coordinated octahedrally with (1) four ammonia molecules in a square planar configuration and (2) either two water molecules or two hydroxyl ions in the axis perpendicular to that plane. The staining group is composed of the ruthenium ion and the associated square planar complex of four ammonia molecules. The staining site in the host molecule must have two negative charges 4.2 A apart and space to accommodate the staining group, lying with its plane perpendicular to the axis between these charges. It is shown that in pectic acid such a staining site occurs between each monomer unit and its next adjacent neighbor. PECTIC MATERIALS will often take up ruthenium red avidly from a dilute solution and in so doing acquire a pale-to-deep red stain. Mangin (1893) noted that the other components of the cell wall were not stained at all and believed that he had found a specific indicator for pectic substances. The reason for this specificity was not explained and has long remained a puzzle. Later it was found that ruthenium red could stain other compounds, such as volutin, i.e., nucleic acid (Meyer, 1904), and oxidized cellulose (FreyWyssling, 1959). The question then arises: What exactly is being stained by ruthenium red? It seems reasonable to expect that a determination of the structure of this compound could reveal the nature of the grouping which complexes with it. This purpose has underlain the present investigation, the first part of which is a crystal-structure analysis of ruthenium red and the second an interpretation of the structure of the stained complex.

Fertilization in barley

Abstract: A B S T R A C T The mature embryo sac of barley consists of an egg, two synergids, a central cell, and up to 100 antipodal cells. At shedding the male gametophyte is 3-celled, consisting of a vegetative cell with a large amount of starch and two sperms having PAS+ boundaries. Before pollination the nucleus and cytoplasm of each synergid appear normal. After pollination the nucleus and cytoplasm of one synergid undergo degeneration. The pollen tube grows along the surface of the integument of the ovule, passes through the micropyle, and enters the degenerate synergid through the filiform apparatus. The pollen tube discharges the vegetative nucleus, two cellular sperms, and a variable amount of starch into the degenerate synergid. Soon after deposition the sperms migrate by an unknown mechanism to the chalazal end of the degenerate synergid. Sperm nuclei then enter the cytoplasm of the egg and central cell, ultimately resulting in the formation of the zygote and primary endosperm nucleus, respectively. Sperm boundaries do not enter egg or central cell, but it was not possible to determine the fate of other sperm components. Degenerate vegetative and synergid nuclei remain in the synergid after fertilization, constituting what are considered to be X-bodies in barley. The second synergid degenerates during early embryogeny. THE ENTRANCE and discharge of the pollen tube into the embryo sac, the role of the synergids, and

Phytochrome controlled nyctinasty in Albizzia julibrissin. II. Potassium flux as a basis for leaflet movement.

Abstract: Excised Albizzia leaflet pairs exposed to red (R) light close within 30-90 min after transfer to darkness. Interruption of darkness by far-red (FR) light at any time after R inhibits closure within ca. 10 min. Similarly, irradiation with R at any time after prior FR promotes closure within ca. 10 min, and the increased rate of closure is independent of the time lapse between the FR and R irradiations. Closure in the dark is inhibited by NaN3 and DNP (5 X 10-4 M), by anaerobic conditions and by externally applied salts of monovalent cations, especially K; it is also temperature sensitive. Pulvinule cells are very high in K. Electron microprobe analysis of cryostated, lyophilized pulvinules reveals that during closure, K is lost from ventral cells and enters dorsal cells. FR before darkness inhibits the former but not the latter process. Thus, K flux appears to control the changes in volume of the pulvinule cells that control leaflet movement. While leaflet closure normally requires a dark period, salts of organic acids such as sodium acetate, propionate, and butyrate cause closure in the light. INVESTIGATIONS on the mechanism of action of phytochrome have recently centered on rapid reactions occurring within seconds or minutes of R and FR irradiation. Such reactions include chloroplast rotation in algal cells (Haupt, 1965), nyetinastic leaflet closure (Fond6ville, Borthwick, and Hendricks, 1966), and adhesion of root segments to glass (Jaffe, 1968; Tanada, 1967). Our investigations on this subject have involved the regulation by phytochrome of leaflet closure in Albizzia julibrissin. This control is exerted within 10 min after pigment conversion (Hillman and Koukkari, 1967; Jaffe and Galston, 1967) through changes in the volume of the motor cells of the pulvinule (Satter, Sabnis, and Galston, 1970). During leaflet closure, subepidermal ventral cells of the pulvinule shrink, and dorsal cells swell. Thus, phytochrome ultimately controls water movement into and out of these cells. We undertook the current investigation in an attempt to define the regulatory processes that precede water movement, in the hope that we could identify reactions close to the primary process controlled by phytochrome. Several years ago Toriyama (1955, 1962) used histochemical techniques to demonstrate K movement 1 Received for publication 4 February 1970. We thank Dr. Horace Winchell and Mr. Malcolm McConnell of the Geology Department, Yale University, for aid in the use of the electron microprobe and Dr. Ian M. Sussex for the use of his cryostat microtome. This work was aided by grants to the third author from the Herman Frasch Foundation and the National Science Foundation. An account of this work was delivered at the XI International Botanical Congress in Seattle, Washington, in August, 1969. out of contracting cells in the primary pulvinus during seismonastic movement of Mimosa pudica. His findings were recently confirmed by Allen (1969), who demonstrated 42K efflux. The transition from light to darkness or the reverse change can control K fluxes which, in turn, control water movement in cells and in cell organelles. Fischer and Hsiao (1968) and Sawhney and Zelitch (1969) independently demonstrated that K fluxes control guard cell turgor in Vicia faba and Nicotiana tabacum, respectively, while Shavit, Dilley, and San Pietro (1968) have shown that light-induced swelling of isolated chloroplasts in the presence of nigericin requires K in the external medium. These several reports, together with Jaffe and Galston's (1967) report of increased electrolyte efflux from Albizzia pinnae during nyetinastic closure, led us to investigate K fluxes in A ibizzia, and their control by phytochrome. Detailed kinetic experiments were also performed to permit evaluation of the ionic flux data. MATERIALS AND METHODS-A lbizzia julibrissin plants were grown from seed (F. W. Schumacher Co.) in a greenhouse as previously described (Satter et al., 1970) until they were 6-12 months old and had several large leaves. Individual plants were transferred to a growth chamber at least three days before experiments, to permit them to adjust to the new environmental conditions (16 hr photoperiod furnished by 9:1 mixed cool white fluorescent and incandescent lights, yielding ca. 1000 ft-c, and a constant temperature of 23 C).

Independence of tissues derived from apical layers in ontogeny of the tobacco leaf and ovary

Abstract: Six different homoplastidic periclinal chimeras of tobacco carrying the plastogene DP, were selected after somatic segregation in heteroplastidic seedlings. Direct observation of the plane of division in epidermal cells of young leaves, and the number and size of sub-epidermal green spots on leaves with the Green-White-White (G-W-W) pattern of variegation, indicated that the ratio of periclinal to anticlinal divisions in L-J during development of the lamina was 1:3100. The number of green and white seedlings obtained from the different chimeral branches indicated a similar frequency of periclinal divisions in development of the ovary. The arrangement of green and white tissue in mature leaves of the various chimeral types indicated the extent of participation by the three apical layers in the initiation of the buttress, development of the axis, and formation of the lamina. During development of the lamina there must be three independent initial-groups present. L-I and L-II initials remain marginal, but early in the growth of the lamina the leading edge of tissue derived from L-III becomes separated from the submarginal (L-II) initials by the products of frequent periclinal divisions of the L-II initials. STABLE PATTERNS of chlorophyll or plastid variegation have been observed and utilized horticulturally for several hundred years. Their interpretation and relationships of pattern to the layers in the apical meristem have been the subject of many investigations (Baur, 1930; Dermen, 1960; Clowes, 1961; Tilney-Bassett, 1963; Burk, Stewart, and Dermen, 1964; Stewart, 1965; Neilsen-Jones, 1969; Stewart and Dermen, 1970). The classical studies of Satina (1944) and Satina and Blakeslee (1941, 1943) and Dermen (1947b, 1953) on cytochimeras have shown that the distribution of derivatives of the different apical layers in cytochimeras can be traced in the shoot and its appendages. The patterns of green and white tissue in plastid chimeras correspond to those in cytochimeras (Dermen 1947a, 1960). The ease with which the plastid patterns can be traced provides more extensive data on the origin of tissues in the mature leaf and on their independence. Studies of periclinal plastid chimeras of tobacco have shown that in the normal ontogeny of the leaf the outer layer of the apical meristem (L-I) gives rise to the epidermis only. The second layer (L-II) gives rise to the sub-epidermal layer of cells over the entire lamina, as well as to the remaining internal cells in an area of irregular width around the edge of the leaf (Fig. 4). Tissue derived from the third layer (L-III) occupies 1 Received for publication 6 April 1970. Cooperative investigations of Vegetables and Ornamentals Research Branch, and Tobacco and Sugar Crops Research Branch, Crops Research Division, Beltsville, Maryland. the remaining central, internal portion of the leaf. Plastid chimeras have also shown that pollen and egg cells are normallv derived from L-II. These relationships have been established for tobacco (Burk et al., 1964), poinsettia and carnation (Stewart, 1965), and many other plants (Dermen, 1960; Tilney-Bassett, 1963; NeilsenJones, 1969). The persistence or stability of periclinal chimeras depends upon the independence of the layers in the apical meristem of the shoot. This independence is maintained by a preponderant, if not exclusive, anticlinal plane of division in the tunica layers in contrast to random planes of division in the corpus. There has been extensive comment in the literature upon the occurrence of periclinal divisions in the outer layers of the apical meristem and their consequences, but few quantitative data have been presented except those of Stewart and Dermen (1970). Similarly the consequences of periclinal divisions below the apical meristem during the development of the st m and its appendages have been described, but good estimates of the frequency of such divisions are not available. Chimeras based on a mutant plastid of tobacco have enabled us to evaluate the stability and role of the apical layers in ontogeny of the leaf and ovary. MATERIALS AND METHODS-Seed was obtained by self-pollinating tobacco plants carrying the plastogene DP1 (mutant plastid DNA) and normal plastids in cells of their second apical layer (G-M-G). The potential for chloroplasts of the three apical layers is indicated by a letter for

Characteristics of salts secreted by tamarix aphylla

Abstract: A B S T R A C T The composition and concentration of salts secreted by the salt glands of Tamarix aphylla L. grown under controlled nutrient conditions were determined. Eight ions, Na, K, Mg, Ca, Cl, NO3, HCO3, and S04, constituted 99 % + of the dry weight of salts secreted by plants grown on half-strength Hoagland's solution. The divalent cations Mg and Ca accounted for most of the cations; HCO3 comprised about 60 % of the anions. The micronutrients B, Mn, Cu, Zn, and Mo were present in enriched concentrations in the secretion. The composition of the secretions was highly dependent on the composition of the root environment. The predominating cation in the saline culture solutions was also the predominant cation secreted. The accompanying anion in the culture solution influences the cation composition of the secreted salt. The concentration of the salt gland secretion averaged 0.5N, a 50-fold increase in concentration over the nutrient solution in which the plants were grown. MANY PLANT and animal species have evolved glands that apparently regulate their salt balance

Shoot and tree production from Aspen tissue cultures.

Abstract: A B S T R A C T Trees were produced from firm white callus tissue of triploid quaking aspen (Populus tremuloides Michx.), initiated on a modified Wolter and Skoog defined medium and subcultured monthly for two years. When subcultured to medium without auxin, kinetin or supplements, but containing 0.15 mg/liter BAP (6-benzylaminopurine), multiple stunted shoots appeared on most inocula. However, at 0.05 mg/liter BAP, only a few vigorous shoots per piece were initiated, but seven rooted on the callus: two in the dark with BAP and five in 200 ft-c of light with 0.04 mg/liter 2,4-D. After proliferation of the roots on the medium surface, four shoots elongated and were planted in semi-sterilized soil, then were given 3100 ft-c of light for rapid growth into trees. Both light sources were on for 16 hr/day. Two trees were also grown from stunted shoots excised from the callus and rooted in soil. THE INDUCTION of complete plants from cell and tissue cultures of herbaceous angiosperms and monocots was reviewed by Pillai and Hildebrandt

Sequence and pattern of lateral root formation in five selected species

Abstract: A B S T R A C T The proximal-distal distribution of the lateral roots of five species was studied. A detailed investigation was carried out on two of the five species, Ceratopteris thalictroides and Cucurbita maxima. A definite pattern of lateral root arrangement, with a degree of variability related to the number of protoxylem poles, was found in all of the species studied. In the fern Ceratopteris, lateral root initiation was found to be related to the segmentation of the apical cell, which in turn determines the distribution of the laterals. In this species the lateral roots occur in a predictable sequence and they are grouped in pairs. In the angiosperms studied, the pattern of lateral root distribution seemed to depend primarily upon a rather strict longitudinal relationship between the lateral root primordia formed opposite any one protoxylem pole. In Cucurbita maxima, 93.7 i 5.02% of the lateral root primordia observed were in a specific sequence. The laterals of this species are also arranged in groups. In the other plants studied, Arachis hypogaea, Victoria trickeri, and Eichhornia crassipes, the laterals were not as regularly arranged, but nevertheless they were found to be arranged in groups along the main root axis and not randomly dispersed. Factors controlling the spacing of lateral root primordia include their relationship with the developing vascular system, a direct effect of the parent root apex, and an effect of older lateral root pri

Cell division in relation to cytodifferentiation in cultured pea root segments

Abstract: A B S T R A C T One mm-thick segments cut 10-11 mm proximal to the root tip of germinating seeds of garden pea Pisum sativum were cultured in sterile nutrient medium containing auxin in the presence and absence of kinetin. In the absence of added cytokinin, pericyclic proliferation occurred, the cortical tissues showed no proliferation and were sloughed off, and a callus tissue of diploid cells was formed. In the presence of kinetin concentrations from 0.1-1.0 ppm cortical cells of the segments were induced to divide, beginning at the third day. From experiments with 3H-thymidine incorporation at different times of culture, from cytological squash preparations and from histological sections it was shown that the cortical cells stimulated to divide by cytokinin underwent DNA synthesis prior to division, were polyploid, and following cell division rapidly underwent cytodifferentiation at 5-7 days to form mature tracheary elements. At 10 days, when over 300,000 new cells had been formed per segment about 16% of these cells had formed traeheary elements. It was concluded that cytokinin, together with auxin, was essential for the initiation of DNA synthesis in the cortical cells, for their subsequent division, and finally for their specific cytodifferentiation.

The effect of light intensity and temperature on plant growth and chloroplast ultrastructure in soybean

Abstract: A B S T R A C T Soybean plants grown in controlled environment cabinets under light intensities of 220 w/m2 or 90 w/m2 (400-700 nm) and day to night temperatures of 27.5-22.5 C or 20.0-12.5 C in all combinations, exhibited differences in growth rate, leaf anatomy, chloroplast ultrastructure, and leaf starch, chlorophyll, and chloroplast lipid contents. Leaves grown under the lower light intensity at both temperatures had palisade mesophyll chloroplasts containing well-formed grana. The corresponding leaves developed under the higher light intensity had very rudimentary grana. Chloroplasts from high temperature and high light had grana consisting of two or three appressed thylakoids, while grana from the low temperature were confined to occasional thylakoid overlap. Spongy mesophyll chloroplasts were less sensitive to growth conditions. Transfer experiments showed that the ultrastructure of chloroplasts from mature leaves could be modified by changing the conditions, though the effect was less marked than when the leaf was growing. LITTLE IS known concerning the influence of light intensities and temperatures characteristic of field conditions on the chloroplast ultrastructure of developing and mature leaves of normal plants. Bjorkman and Holmgren (1963) using the light microscope showed that their higher light intensity destroyed the chloroplasts of shade ecotypes of Solidago virgaurea, whereas chloroplasts from exposed ecotypes were unaffected. The effect of light intensity on the ultrastructure of chloroplasts from pigment-deficient mutants was investigated by Walles (1965), Schmid, Price, and Gaffron (1966), Clewell and Schmid (1969); the effect of temperature and light on the greening of detached, etiolated leaves by Klein (1960), Eilam and Klein (1962); and the eff ect of transference of dark-grown seedlings to light by \'IcWilliam and Naylor (1967). This study concerned differences in growth rate, leaf anatomy, chloroplast ultrastructure, and chemical composition in soybean plants grown in cabinets under combinations of temperature and light similar to those occurring naturally. Comparisons were made with plants grown outside and in the glasshouse. The plants used were well beyond the seedling stage.

Isolation of thermophilic fungi from self-heated, industrial, wood chip piles.

Abstract: Thermophilic fungi isolated from self-heated wood chips stored at a paper factory included Chaetomnium thermophile var. coprophile Cooney & Emerson, C. thermophile var. dissitum Cooney & Emerson, Humicola grisea var. thermoidea Cooney & Emerson, H. lanuginosa (Griffon & Maublanc) Bunce, Sporotrichum thermophile Apinis, Talaromyces emersonii Stolk, T. thermophilus Stolk, and Thermoascus aurantiacus Miehe sensu Apinis. Fewer species were present in fresh chips and in chips from unheated piles. The thermotolerant fungus Aspergillus fumigatus Fresenus was recovered from all chip samples. Incubation of whole or ground chips at 50 C on Emerson YpSs Agar (Difco), on 2% malt agar, and in damp chambers was necessary and sufficient for enrichment and detection of thermophilic species present in the samples. Use of a lower temperature or of only a single enrichment medium resulted in incomplete detection of species present. Enriching in atmospheres of tank N2 and of C02-supplemented air, and plating on a variety of nutritionally restrictive media, failed to increase the number of thermophiles isolated. Dilution-streak plating was the most efficient and effective method for isolation and purification; addition of 100 units per ml of both streptomycin sulphate and penicillin G to isolation media facilitated purification. It was concluded that thermophilic fungi are abundant in selfheated wood chips, and together with thermotolerant fungi contribute to heating and biodeterioration.

The pollen wall of Canna and its similarity to the germinal apertures of other pollen.

Abstract: A B S T R A C T The pollen wall of Canna generalis Bailey is exceptionally thick, but only a minor part of it contains detectable amounts of sporopollenin. The sporopollenin is in isolated spinules at the exine surface and in the intine near the plasma membrane. There is no sporopollenin in the > 10 ,u thick channeled region between spinules and intine. We suggest that the entire pollen wall of C. generalis is similar to the thick intine and thin exine typical for germinal apertures in many pollen grain types. Considered functionally, the Canna pollen wall may offer an infinite number of sites for pollen tube initiation and would differ significantly from grains that are inaperturate in the sense of an exine lacking definite germinal apertures. THE CANNACEAE are represented by a single genus, Canna, and approximately 50 species. The extensive use of Canna as an ornamental has resulted in numerous hybrids. In a pollen morphological investigation of 48 horticultural varieties of C. indica significant differences were noted in wall ornamentation, sterility, and size (Nair, 1960). The exine stratification patterns, however, have been difficult to interpret as Erdtman (1952) suggested. Sporopollenin as part of an exine is recognized only in spinules at the pollen wall surface but staining of Canna microspores with osmium indicated that there were inclusions within the intine and in the tryphine on the wall surface which looked like sporopollenin. To substantiate the presence of sporopollenin in the above nonexinous locations we followed the disintegration of Canna pollen caused by the acetolysis method of Erdtman (1960). It became evident that the entire wall was similar to the greatly thickened intine and thin exine common to the germinal apertures of many pollen grains. We have drawn upon original electron micrographs of Centrolepis aristata (R. Br.) Roem. and Schultz. and Macrozamia reidlei (Gaud.) C. A. Gardn. to amplify the latter aspect of our results.

The pollination ecology of pedicularis in colorado

Abstract: The pollination ecology of seven Pedicularis species was studied in the montane-alpine ecotone of the Front Range of the Colorado Rocky Mountains. No species was found to self-pollinate, and all species were primarily pollinated by bumblebees (Bombus Latr.). Foraging behavior of insects was recorded cinematographically and stereophotographically and correlated with the form and operation of .the pollination mechanism of each species. Further correlations were made between phenology of flowering and development of pollinator colonies, altitudinal distributions of plant and pollinator species, pollinator bionomics and analyses of corbicular loads for 1014 Pedicularis pollinators, and interspecific pollination coactions of sympatric plant species. The concepts of caste adaptation of pollinators, multiple adaptation of pollinators, fidelity of foragers, competition for pollinators, sharing of pollinators, and coadaptive evolution in stress environments are evaluated in view of the data presented. PREVIOUS REPORTS of the form and function of pollination mechanisms in Pedicularis by Muller (1873), Sprague (1962), Faegri and van der Pijl (1966), and A\Jacior (1968a, 1968b, 1969) have suggested a high degree of correlation between the bionomics of the plants and their pollinators. The great variety of flower form in the genus, which includes more than 500 species, seems to indicate a diversification closely related to and determined by coaction with the form and behavior of pollinators. The present study relates pollination of flowers of 7 species in the montane-alpine ecotone of the Front Range of the Rocky Mountains in Colorado to the ecosystem dynamics of the region. These ecosystems have been well-documented by Marr (1961). Clements and Long (1923) conducted experimental pollination studies in the nearby Pike's Peak region on selected plant genera other than Pedicularis. Data presented here constitute part of a four-year study of the pollination ecology of the East Slope of the Front Range and do not include information on Pedicularis groenlandica previously published (Macior 1968a). M4ETHODS AND MATERIALS-During the period 1966-1969, 7 species of Pedicularis were studied for their pollination relationships in the Front Range of the Colorado Rocky Mountains from Niwot Ridge in Boulder County to Jefferson in Park County over an altitudinal range from 8,30012,800 ft above mean sea level. Records of blooming phenology were kept. Self-pollination IReceived for publication 17 January 1970. The author is grateful for field and technical assistance provided by his students, Stephen Adamowicz, David Brzoska, Dennis Franke, Susan Leach, and Chrystyna Strileckyj. This study was supported by National Science Foundation grants GB-5184 and GB-7779. potentials for each species were determined by comparing fruit development on four or more plants caged to exclude pollinating insects with fruit development on an equal number of uncaged plants in the immediate vicinity of the caged ones. In 4 species populations at more than one elevation were tested. Cages were made of 18 X 14 mesh galvanized wire screening and were placed over the plants while flowers were still in bud. Critical measurements and photographs of flower structure were made in the field from living materials. Foraging behavior of insects was recorded in the field on 16 mm color film at a recording speed of 32 frames/sec and individual frame exposures of 1/320 sec. Motionand single-frame analyses of these records were made. Stereophotographic behavioral studies were also carried out at a distance of 3 in. from the subject. Insects foraging on Pedicularis were collected and identified, and their behavior noted. Sounds of wing vibrations of foragers in flight and foraging were recorded on magnetic tape for P. racemosa pollinators. Corbicular loads of pollen from Bombus foragers were analyzed by methods previously described (Macior 1968a). All foragers on the flowers were collected except for hummingbirds, which were recorded from observations only. Records were also kept of air temperatures during insect collection, times of day when collections were made, and total man-hours of collecting for each plant species. Only those plant populations that provided abundant flowers concentrated in one area were selected for study, making possible substantial collections of foragers. Pedicularis bracteosa Benth. var. paysontana (Pennell) Cronquist was studied below Berthoud Pass (10,700 ft); P. crenulata Benth. at Jefferson in South Park (9,500 ft); P. grayi Nels. near Clear Lake above Georgetown

Somatic genetic analysis of the apical layers of chimeral sports in chrysanthemum by experimental production of adventitious shoots.

Abstract: A B S T R A C T Many commercial chrysanthemum cultivars display unusual somatic variability. The 'Indianapolis' family of chrysanthemtum sports was analyzed for the genetic potential for color of each of the three layers in the apical meristem of their shoots. Populations of each cultivar were grown and sectors and off-color plants recorded. The location of the pigment within cells and between tissues was determined by microscopic examination of free-hand sections of fresh petals. Adventitiouis buds were forced from the stems of each cultivar by excising all normal lateral buds. These observations showed 12 of the 16 'Indianapolis' cultivars to be perielinal chimeras. Adventitious shoots often originated from two or more cells, derived from at least two different apical layers, and thuis were themselves periclinal chimeras. While somatic mutation is the ultimate source of the variability in 'Indianapolis' chrysanthemums, the most frequent type of sporting resulted from the loss in mitosis of a chromosome carrying a supressor for the formation of yellow chromoplasts, giving a yellow sector or shoot. Sectors resulting from rearrangement of layers in the

Incompatibility and the pollen economy of jepsonia parryi

Abstract: A B S T R A C T Jepsonia parryi (Saxifragaceae) has heterostylous flowers and is strongly self-incompatible. Pin flowers have long styles, large stigmas, short stamens, and numerous, small pollen grains with finely sculptured walls. Thrum flowers have short styles, small stigmas, long stamens, and fewer, larger pollen grains with coarsely sculptured walls. Pin plants and thrum plants occur in a 1:1 ratio in field populations. Although the insect pollinators of J. parryi transfer ample compatible pollen to pin and thrum stigmas to account for full seed production, much of the pollen deposited on stigmas is incompatible. Analysis of the pollen deposits on stigmas collected from field populations indicates that compatible "legitimate" pollination of pin and thrum flowers is essentially random and is not obviously aided by floral dimorphism. It is suggested that although heterostyly had a positive adaptive value in the past evolutionary history of Jepsonia it is no longer adaptive under the present pollination regime, although it is maintained because of its strong genetic fixity. THE OCCURRENCE of heterostylous flowers in the small southwestern genus Jepsonia is unique in the Saxifragaceae and undoubtedly represents an instance of the independent evolution of heterostyly in the family (Ornduff, 1961). The purpose of this paper is: (1) to document the morphological characteristics associated Nith heterostyly in Jepsonia parryi (Torr.) Small, one of three species in the genus; (2) to demonstrate that heterostyly is associated with a strong incompatibility system in this species; and (3) to present data concerning the pollen economy of this species, that is, the production, distribution, and retention of pollen in natural populations. Of particular importance to the interpretation of the biological significance of heterostyly is the degree to which the morphological and physiological features associated with the heterostyly of J. parryi form an integrated reproductive system.

Assessment of evolutionary affinities in Gossypium by protein electrophoresis.

Abstract: Protein band patterns from 25 species of Gossypium were obtained by electrophoresis of crude seed extracts on polyacrylamide gel. Band homologies between species were verified by electrophoresis of a mixture of their extracts. The patterns were found to be largely consistent with the conventional classification of the diploids into 6 genomic groups, A-F. However, G. triphyllum and G. bickii showed unique patterns differing respectively from those of the B and C groups, and G. australe showed closer affinity with the Arabian Ethan with the Australian C-genome species. Affinities among the D-genome species were different from those implied by their former grouping into taxonomic sections but remarkably similar to those indicated in the most recent taxonomic revision of the genus. They were classifiable into two subgroups, ,B and e. The clustering pattern of the diploids based on correlation coefficients calculated from densitometer curves of the electrophoretic spectra suggested that the genomic groups were derived from an African progenitor type, and that the American ,8 and E subgroups, most closely related to the African Band the Arabian E-genome groups respectively, evolved under comparative mutual isolation, possibly separated by the Tertiary Amazonas basin. SOME 30 diploid species of Gossypium are recognized. These occur in arid, tropical, and subtropical regions around the world. With some exceptions their geographic ranges, characterized by a disjunct population structure, are small and isolated, suggestive of relicts from an ancient pantropic distribution, (Fryxell, 1967; Saunders, 1961). Primarily on the basis of sterility barriers and the amount of chromosome pairing in interspecific F1 hybrids the species have been classified into genomic groups (Beasley, 1942) corresponding with their geographic dispersion. Eleven species scattered along the Pacific Coast of America (Fig. 54) and 9 or 10 in Australia comprise the Dand C-genome groups respectively, while the E-genome group as loosely defined includes five species ranging from the Persian Gulf into eastern Africa. The B-genome species show an exceptional distribution with two on the Cape Verde Islands and two in southwestern Africa one of which, G. anomalum Wawr. ex Wawr. & Peyr., also occurs 1 Received for publication 13 April 1970. This stuidy is based in part upon a doctoral thesis submitted by the junior author to the Graduate School University of California, Los Angeles. Support provided by NSF grant GB-7337 to the senior author for development of the electrophoretic techniques is gratefully acknowledged. The authors are indebted to Dr. 0. L. Hall and Dr. E. A. Hultin for help with the protein extraction method; to Dr. T. R. Richmond, Dr. E. L. Turcotte, Dr. S. C. McMichael, and the late Mr. L. I. Benedict of the U.S.D.A. Agricultural Research Service, and to Dr. R. Hartman for seed stocks; also, to Dr. L. L. Phillips and Dr. P. A. Fryxell for making available their experimental collections. 2 Present address: No. 1 Pvidaungsu Lane, off Goodliffe Road, Yankin P.O., Rangoon, Burma. widely dispersed north of the equator from the Gulf of Aden to the Niger Valley. The A-genome species G. herbaceum L. and G. arboreum L., the only diploids to produce cotton, presumably were derived from a type similar to the wild G. herbaceum var. africanum (Watt.) Hutch. & Ghose indigenous to the bushveldt of southern Africa. Since the advent of man, these two species have spread in cultivation across Africa and Asia to Indonesia. Individually the wild species are remarkably homogeneous in contrast to the cultivated ones. Knight (1949) observed that G. anomalum, the most widely distributed of the wild diploids, showed less variation over a wide range of African desert localities than is commonly found in a field of cultivated G. arboreum; and Saunders (1959) was unable to distinguish morphologically between southern and northern elements of the disjunct anomalum distribution. Leaf and capsule attributes providing the basis for previously reported varietal differences within G. harknessii Brandg. and G. davidsomii Kell. were found by Phillips and Clement (1967) to be variable throughout the ranges of both species. However, an exception to the morphological uniformity of the individual sDecies appears to occur among the Somaliland elements of G. somalense (Guirke) Hutch. (Saunders, 1961). As a rule hybrids obtained between species of the different geographic groups show less than an average of six bivalents with the notable exception of A X B hybrids, while those obtained between species within the same group show essentially the maximum number, 13 (Phillips, 1966).

Populational and genetic studies of a homosporous fern—osmunda regalis

Abstract: The mating system and the genetic system of the homosporous fern Osmunda regalis were investigated. Seven populations from western Massachusetts were sampled. All the sporophytes investigated were found to be heterozygous for zygotic lethals. Morphological studies of the gametophytes indicated an intergametophytic mating system when the gametophytes were spatially and chronologically situated to exchange male gametes. Genetic studies evidenced a genetic system based upon duplicate loci. HoMOSPOROUS FERNS are vascular plants which must deal with at least two genetic problems not confronting seed plants. They must contend with a haploid phase which is free living, long-lived, morphologically and physiologically complex, and which, in many cases, may have a distinct ecology from the diploid phase. Secondly, homosporous ferns undergo at least periodic intragametophytic selfing with its consequent obligate homozygosity (Klekowski and Baker, 1966). Studies of the reproductive biology of selected species of ferns have evidenced numerous adaptations which have evolved in response to the above aspects of their life cycles. Most of these studies have dealt with the phenomenon of intragametophytic selfing and its effect on the genetic system (Klekowski and Baker, 1966). Since the gametophyte generation is the sexual generation, any evolutionary strategy employed to decrease the frequency of intragametophytic mating in favor of intergametophytic mating must be based ultimately upon gametophyte adaptations. Klekowski (1969a) discussed these adaptations and considered their adaptive significance to a taxon's mating system with relation to its ecology. Experimental confirmation of some of these speculations is available for the fern Ceratopteris thalictr-oides (Klekowski, 1970a). In addition to studies of gametophyte morphology, it is also important to understand what genetic systems have been evolved in response to these "life-cycle characteristics." Estimates of the frequency of lethal or semilethal mutations in populations, the inheritance of these mutations (diploid or polyploid), and the extent to which genetic variability is concealed due to epistatic I Received for publication 15 May 1970. I should like to extend my thanks to Mr. Kenneth Abbt for technical assistance; to Mr. Harry Ahles for help in locating the populations; and to Dr. D. W. Bierhorst for mnany useful suggestions. This investigation was supported by NSF grant GB8721 and a grant from the Research Council, University of Massachusetts, Amherst. effects are all meaningful parameters of the genetic systems present in these plants. Such data are available for selected taxa but seldom for a population (Klekowski and Lloyd, 1968; Klekowski, 1969b, 1970a, b). This paper describes such a study on the royal fern, Osmunda regalis L. Osmunda regalis was chosen because of certain specific attributes. It is a member of one of the more ancient homosporous fern families, the Osmundaceae, with a fossil record extending to the Permian (Hewitson, 1962). The genus Osmunda can be classified in three subgenera, Osmunda, Osmundastrum, and Plenasium. The subgenus Osmunda, which includes 0. regalis, is the most ancient of the three subgenera, with a fossil record extending back to the Cretaceous (Miller, 1967). All species in the three extant genera which have been studied cytologically have the same chromosome number, n = 22 (Fabbri, 1965). Thus, although there is karyological evidence for a polyploid origin of this base number (Tatuno and Yoshida, 1966, 1967), the present generic base number of 22 may go back to, if not beyond, the early Cretaceous (assuming a monophyletic origin of this base number). It therefore is likely that this genome has been in existence for over 100 million years, ample time for at least partial genetic diploidization to have occurred. Osmunda regalis is distinct also in two other ways which were advantageous to this study. This fern does not reproduce vegetatively as extensively as some other ferns (i.e. Pteridium); thus a population will consist of numerous plants which were of sexual origin. Secondly, the gametophytes are distinct enough to be identified in the field; consequently, gametophyte morphologies of field and laboratory-grown plants could be compared. MVIATERIALS AND METHODS-Seven populations of 0. regalis were studied. All are in western Massachusetts and have been given the following

Secretory cells of lily pistils. i. fine structure and function

Abstract: The fine structure of the cells which line the canal of Lilium longiflorum pistils confirms the secretory function which has been ascribed to them. The cells differ in structure from the secretory cells which cover the stigma surface and are therefore referred to as canal cells rather than stigmatoid cells. Their most striking feature is an elaborate wall, 8-14 , in maximum depth, on the side facing the canal, which with associated structures, we term the secretion zone. Pollination, which triggers chemotropic activity in the style and secretory activity in the canal cells, is not correlated with marked changes in the fine structure of the canal cells. The canal cells appear to fit well into that category which Guinning and Pate have termed "transfer cells." A DISTINCTIVE feature of fertilization in angiosperms is that the pollen tube must grow through female sporophytic tissue in order for fertilization to be effected. In Petunia hybrida and Gossypium hirsutum the pollen tubes grow between special cells of the pistil which constitute what has been termed conducting or transmitting tissue. In P. hybrida the stigmatic secretion, its function, and the nature of the cells which produce it have been studied by Konar and Linskens (1966a, b). Jensen and Fisher (1969) have described the fine structure of the cells of the stigma and style of G. hirsutum in relation to the growth of the pollen tubes through the pistil. In Lilium longiflorum growth of the pollen tube through the pistil is facilitated by a canal. The cells of the stigma surface and the cells lining the canal, most frequently referred to as stigmatoid cells, are presumably secretory in nature. Rosen (1961) reported that the stigmatic exudate of L. longiflorum stimulated both germination and tube growth of L. longiflorum pollen in vitro. Yamada (1965) noted that the stylar canal of L. lonrtiflorum is filled with a mucilaginous material following pollination. He analyzed this material cytochemically and stressed its presumed nutritive role for the growing pollen tubes. Welk, M\lillington, and Rosen (1965) concluded that a major function of the secretory product of the stigmatoid cells of L. regale and L. leucanthum was chemotropic guidance of the pollen tubes through the pistil to the embryo sacs. Rosen and Gawlik (1966) noted a difference in the fine structure of the tips of pollen tubes growing in compatible as opposed to incompatible pistils of L. longiflorum. They suggested that compatible tubes may be able to take up secretion products of the pistil 1 Received for publication 17 April 1970. Supported by grant GB-5402 from the National Science Foundation. Lily bulbs were donated by W. A. Gloeckner and Co., New York, New York. through their tips whereas tubes growing in incompatible pistils cannot. Kroh et al. (1970) have shown that L. longiflorum pollen tubes growing in pistils which had been fed labeled myo-inositol can incorporate label from pistil exudate into pollen tube cell wall. Thus the secretions found on the stigmatic surface and in the stylar canal have been implicated in nutrition, chemotropism, and incompatibility reactions of pollen tubes. The present paper describes the fine structure and discusses the function of the secretory cells. MATERIALS AND METHODS-Pistils and pollen were obtained from flowers of L. longiflorum, cv. Ace, Croft, and Georgia. The plants were grown in the department greenhouse under prevailing light. Pollen was used fresh or after storage in petri dishes in the refrigerator for up to several weeks. Cut flowers were placed in a 25 C room under continuous illumination 24 hr before pollination and kept there until fixation. For all pollinations stamens and perianth were removed from flowers and the pollen applied liberally with a wood applicator to the entire stigmatic surface. Pistils were immersed in 3 % glutaraldehyde adjusted with 0.1 M phosphate buffer to pH 6.8 or 7.3 and immediately cut transversely under fixative into 0.5 mm slices. Fixation was at room temperature for 2 hr and was followed by postfixation in 2 % osmium tetroxide buffered as for fixation. Dehydration through an ethanol series was followed by propylene oxide and flat embedment in Epon. Sections were usually stained with uranyl acetate and lead citrate. Barium permanganate (1 % for 5 min) was sometimes employed as the only stain. Addition of 0.1 M sucrose to the fixative and post-fixative had no observable effect. For autoradiography, pistils, with a portion of the receptacle still attached but with the stamens

Water potential, temperature, and kinetin effects on seed germination in soil and solute systems.

Abstract: A B S T R A C T Germination of lettuce and wheat in soil is reduced by a decrease in water potential, but a significant temperature-water potential interaction exists for lettuce. At 35 C kinetin permits lettuce germination at 0 and -1.1 bars, and at 25 C and 15 C it enhances germination at lower water potentials, causing 30% germination at -8.0 bars. Wheat germinates well at -8.0 bars, but no germination occurs at -14.9 bars; temperature had little effect on wheat germination. Germination in soil and solute systems was compared to determine the usefulness of solute germination data for predicting germination in dry soil. Total germination of lettuce in polyethylene glycol-6000 may approximate total germination in soil at the same water potential, but germination rates differ widely for the two systems. Kinetin-treated lettuce seeds nearly completed germination in two days in polyethylene glycol solutions, but five days were required for similar germination percentages in the soil. Sucrose is not useful for simulating soil water stress; wheat seeds germinate at -14.9 bars in sucrose but fail to germinate in soil at the same potential, and germination is more rapid in sucrose than in the soil. WATER POTENTIAL and temperature are important ,environmental factors affecting seed germination. Individually, each factor has been studied rather 'extensively, but little is known about the effects of water stress at different temperatures. Conclusions about the effects of water stress at one temperature are not valid at other temperatures if a water stress-temperature interaction exists. This paper reports the results of experiments having a two-fold purpose: to determine (1) the

Mucilage-producing cells in the seed coat of plantago ovata: developmental fine structure,

Abstract: A B S T R A C T As the ovule of Plantago ovata matures into a seed its epidermal cells are transformed from undifferentiated parenchyma to thin-walled containers of almost pure mucilage. During this process the volume of the cells increases 60-80 fold, and the protoplast degenerates to a remnant. Rapid cell expansion begins with pollination and is accompanied by an increase in the size of the nucleus and nucleolus, a change in the random arrangement of ribosomes, a decrease in the thickness of cell walls, and synthesis of starch. Deposition of mucilage inside vacuoles and between the plasma membrane and cell wall accompanies a marked increase in the number and size of Golgi vesicles. Histochemical evidence using the thiocarbohydrazide-osmium vapor method shows polysaccharide to be present within Golgi vesicles while they are still attached to the Golgi apparatus. Mucilage deposition is associated with further cell expansion, separation of the protoplast from the cell wall, fusion of vacuoles and extra protoplasmic space, and the disappearance of starch. TIIE OUTERMOST CELL LAYER of the seed in the genus Plantago contains little but mucilage. The seed-produced polysaccharides of several Plantago