摘要:

Fruticose and crustose forms ofAspicilia desertorum(Kremp.) Meresch. are recorded from Western Colorado in microhabitats beneath snow patches and on exposed rock surfaces, respectively. For single populations, microenvironmental variation in substrate, temperature, light intensity and water availability is directly related to continuous morphological variation. Functional variation with habitat is evident in growth form, stage of apothecial development, calcium oxalate pruinosity, anatomical disposition of unidentified crystalline material, cortical anatomy and continuity, numbers of algal cells per unit weight of thallus, medullary anatomy, maximum thallus water content (or water‐holding capacity) and relative thickness of hyphal walls. These multivariate relationships define ecomorphological syndromes and a pattern of variation with parallels at a higher phytogeographic level.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07747.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

In a study of intra‐ and interpopulation variation in seed glucosinolates, remarkable uniformity was found among individuals within the two chemically distinct subspecies of East CoastCakile edentula. Glucosinolates were used as taxonomic markers in a study of hybridization between ssp.edentulaand ssp.harperiwhere they form mixed populations on the Outer Banks of North Carolina. Thirteen plants with hybrid chemical profiles were detected in a sample of 89 individuals from four populations; the zone of hybridization is narrow, and has persisted for at least eight years. Artificial hybrids of the two subspecies are additive for kinds and intermediate for proportions of seed glucosinolates, and families of F2's show a range of recombinant chemical profiles. Natural hybridization was confirmed by recovering hybrid and parental types in 47 progeny of three presumptive wild hybrids. Glucosinolate profile characteristics segregated independently of the segregation patterns for fruit length and seed weight. Selection against particular glucosinolate phenotypes is one possible mechanism maintaining this narrow hybrid zone on the Outer Banks.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07748.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The ultrastructure of developing and mature nonarticulated laticifers inAsclepias syriacaL. (the common milkweed) was studied by conventional fixation and staining techniques and by osmium impregnation techniques. The mature laticifer protoplast inA. syriacapossesses a large central vacuole with an intact vacuolar membrane. Formation of this vacuole apparently results from dilation and subsequent enlargement of endoplasmic reticulum and possibly in part by fusion of smaller vacuoles and limited cellular‐lytic autophagy. Widespread digestion or autophagy of cytoplasm within vacuoles is not evident. Nuclei, mitochondria, dictyosomes, and small vesicles are the most prominent components distributed in the peripheral cytoplasm. Plastids appear to degenerate as the laticifer matures. The specialized cellular component, latex, which is the vacuolar content of the laticifer, is interpreted to be produced in the cytoplasm and subsequently incorporated into the large central vacuole. Rubber globules, the most prominent latex component, are surrounded by a membrane that does not have a trilaminate structure. Globules are associated with an electron‐dense fibrillar component in the vacuole.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07749.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Ultrastructural changes occurring in the central part of the apical meristem of the SDPXanthium strumarium, induced to flower by a single 16‐hr long night, were quantitatively investigated using stereological methods and compared to the changes previously reported in other species, particularly the LDPSinapis alba. Changes detected inXanthium, which are also found in other species, included: increase in cellular, cytoplasmic, cytoplasmic matrix and nucleolar sizes, change in nucleolar structure; increase in mitochondrial number and chondriome size, increase in dictyosome number. These changes are believed to be essential for floral evocation because of their universality. Other changes were specific toXanthiumand not detected inSinapis. Accordingly, they were thought to be accompanying nonessential events of floral evocation inXanthium. These changes included an increase in the number of plastid profiles and in plastidome size. The size of the nucleus, chromatin and vacuolar apparatus, as well as the number of vacuolar profiles, did not change inXanthium, contrary to what was observed in other plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07750.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Both field measurements and a computer model were used to study the interception of photosynthetically active radiation (PAR) byAgave deserti(Engelm.), a desert CAM plant with a basal rosette of massive opaque leaves. PAR interception was determined in the winter and the summer for upper and lower leaf surfaces on a plant with about 60 leaves. Total daily PAR on the leaf surfaces was approximately 10 mol m‐2for a winter day and 20 mol m‐2for a summer day. For a PAR of 15 mol m‐2, the nocturnal increase in acidity was about 0.6 mol m‐2for both leaf surfaces and various leaf orientations, except for the oldest most horizontal leaves where the increase was less than half as large. The acidity increase measured in the field was 90% saturated at 25 mol m‐2. Thus, daytime PAR in the desert is often limiting for the nocturnal acidity increase, especially for the lower leaf surfaces. Simulated tilting of the plant by 55° so that the vertical axis pointed to the sun at solar noon on a winter day increased the PAR incident on the upper surfaces of the leaves, but did not affect the total nocturnal increase in acidity by the whole plant. Although simulated removal of alternate leaves increased the PAR per unit leaf area for the remaining leaves, it reduced the total increase in nocturnal acidity of the whole plant by 31%. PAR interception by plants on slopes facing steeply north, east, or west was substantially reduced compared to the horizontal. Thus, the model proved to be quite useful for quantifying the relation between leaf orientation, PAR interception, and nocturnal increases in acidity byA. deserti, and it indicated that the lower frequency of plants on north‐ compared to south‐facing slopes was due to PAR limitations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07751.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Barinophyton citrulliformeis definitely proven to be a tracheophyte. The vascular cylinder of the main axis is an exarch protostele composed of tracheids having a continuous secondary wall folded into protrusions into the cell lumen. These protrusions delineate the position of annular thickenings which were deposited earlier than the continuous secondary wall. Between successive protrusions, the later‐deposited secondary wall is interrupted by minute pitlike structures. It is suggested that the secondary walls of the tracheids were laid down in a two‐phase depositional sequence. The fertile system ofB. citrulliformeconsists of a main axis bearing spirally arranged strobili. The strobilus consists of an axis that bears two alternate rows of sporangiferous appendages. The sporangiferous appendages are borne laterally along the strobilar axis and recurve abaxially around the axis. The sporangia are attached along the inside curve of the appendages, one sporangium per appendage, each containing both microspores and megaspores. This species thus exhibits sporangial heterospory which is considered to be an adaptation to an aquatic habit and the sporangia are considered to be functional analogs of the sporocarps ofMarsilea. The interpretation of the strobilus is morphologically identical to Ananiev's interpretation of the strobilus ofPectinophyton bipectinatum;consequentlyP. bipectinatumis here transferred toBarinophytonasB. robustiuscomb. nov.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07752.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The genusMollugohas been reported to have species which are C4plants and a C3‐C4intermediate. In the present paper, we report on the anatomy and photosynthetic physiology of three additional species in the Molluginaceae,M. pentaphylla, M. nudicaulis, andM. lotoides, all of which possess some anatomical and physiological features of both C3and C4plants. Most notable among the variable C3‐C4features are C4‐like bundle sheath cells, along with a C3‐like arrangement of palisade and spongy parenchyma.M. nudicaulisappeared to have lower photorespiration based on its CO2compensation point and lower oxygen sensitivity of photosynthesis. The occurrence of polyploidy within this group of plants and its relationship to lower photorespiration or evolution of these species is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07753.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Strobe photographs were taken of over 200 spinning samaras from seven species of trees. These were used to measure the rate of descent, angular velocity, orientation, and other parameters of the samaras as they fell. These data were then used to compare the aerodynamic behavior of samaras, helicopters, and theoretical ideal rotors. Plotting morphological data for each samara against its rate of descent showed that this rate was highly correlated with the square root of the samara's wing loading (samara weight divided by wing‐surface area). This plot demonstrated the existence of two distinct groups of samaras, distinguished by their morphology, spinning motion, and rate of descent. These results are of greatest use in characterizing local dispersal patterns.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07754.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Maturation of the metabasidium ofAuricularia fuscosuccineawas followed with light microscopy and transmission electron microscopy. The basidium was divided into four compartments by septa which developed centripetally as in hyphae. Each septum formed a septal pore apparatus with imperforate pore caps. A band of electron‐dense material was situated in the middle of the septal pore. There was a large increase in the volume of cytoplasm, excluding vacuoles, in each compartment during sterigmal outgrowth. Compartments were evacuated in basipetal sequence and vacuole enlargement began at the base of a compartment only when sterigmal formation was well advanced. The septal pore apparatus was intact until late in maturation of a compartment when septal swellings occluded the pore. The metabasidial wall was differentiated from those of other hymenial and subhymenial cells. The pattern of basidial maturation is compared with that in other phragmobasidiate and holobasidiate fungi. Use of the septal pore apparatus for phylogenetic and taxonomic purposes is discussed, as is the concept of primary and adventitious septa.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07755.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The responses of four populations ofSolidago sempervirensto salt spray at Island Beach State Park, a barrier beach in Ocean County, New Jersey, were examined under both field and greenhouse conditions. At increasing distances from the ocean, these populations were Primary Dune (PD), Dune Hollow (DH), Intermediate (INT), and Bayshore (BAY). Salt deposition on cheesecloth traps was found to drop significantly from PD to BAY. Population responses to the salt spray gradient were monitored by examining leaf stomatal and trichome densities, leaf thickness, and the salt spray tolerance of genotypes established in the greenhouse. No significant differences in either stomatal or trichome density were found among populations in the field. Leaf thickness of field plants at the PD site was significantly greater than the DH, INT, or BAY plants: however, unsprayed plants of these populations in the greenhouse did not vary significantly in leaf thickness, and for sprayed plants, leaf thickness varied only in relation to intensity of salt application. Thus, the differences in leaf thickness of field populations were not genetically based. Both nonexpanded and fully expanded leaves of BAY plants consistently showed the greatest percentage leaf damage following both low‐ and high‐intensity artificial salt spray, indicating possible selection for population differences in salt spray tolerance.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07756.x

出版商:Wiley    

年代:1980

数据来源: WILEY