摘要:

Seventeen greenhouse‐grown grasses from the Nebraska Sandhills region were surveyed for foliar stomatal density and distribution, closed guard cell lengths, open stomatal apertures, and surface characteristics (using scanning electron microscopy), surface conductance (using a steady‐state porometer), and drought‐induced leaf modifications. Leaves of C3species exhibited a proclivity toward being amphistomatic or hyperstomatic, while C4species tended to be more hypostomatic. Leaf modification, when it occurred, resulted in the enshrouding of the adaxial surface. Conductance data showed functional amphistomaty in most species, revealing differential functioning of adaxial and abaxial stomata. Conductance patterns were not closely related to stomatal aperture per unit area leaf surface or to stomatal distribution patterns. Lowered adaxial: abaxial conductance ratios, increased stomatal density, reduced stomatal size, and less drought‐induced leaf modification were seen in C4grasses as compared with C3grasses. C3range and C3meadow species did not differ in conductance ratios, density ratios, or stomatal size, although meadow species exhibited much greater drought‐induced leaf modification. Postulations involving correlation of adaxial: abaxial conductance ratios to stomatal distribution patterns, and assumptions of stomatal distribution based upon habitat and/or photosynthetic pathway may be erroneous. These characteristics may be of limited usefulness as morphological indicators in the search for drought‐tolerant ecotypes of prairie grasses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb15641.x

出版商:Wiley    

年代:1995

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11519.x

出版商:Wiley    

年代:1995

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11520.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

Mielichhoferia elongata, one of the so‐called “copper mosses,” has a broad but highly disjunctive geographic distribution and is rare throughout its range. A genetic analysis of 30 populations based on a survey of 21 allozyme loci reveals the following. 1) Total gene diversity at the specific level is high (0.41). 2) Within‐population diversity is low, and over 90% of all genetic variation is among rather than within populations (mean GST= 0.93). 3) There is little differentiation in allele frequencies between North American and European populations. 4) Populations consist of one to six multilocus genotypes; 13 of the populations appear to consist of a single clone. 5) Colorado populations contain a tremendous reservoir of genetic variation (88% of all alleles found in the species in North America and Europe occur in one or more Colorado populations). 6) Populations in the eastern and western United States, and in Europe, contain subsets of the allelic diversity found in Colorado. The genetic structure ofM. elongatasuggests repeated dispersal and founding of populations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb15642.x

出版商:Wiley    

年代:1995

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11522.x

出版商:Wiley    

年代:1995

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11523.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

Nuclear DNA contents of developing sperm were estimated for 17 species of bryophytes by cytophotometry in squash preparations of antheridia after Feulgen staining. Genome sizes are in the lower end of the range for land plants. Two homwort C‐values have the lowest recorded for bryophytes at 0.17 and 0.26 pg DNA per nucleus. In liverworts, C‐values range from 0.49 pg inBlasia pusillato 4.05 pg inPellia epiphylla, while moss genome sizes are less variable, ranging from 0.38 pg inTakakia ceratophyllato 0.92 pg inAtrichum oerstedianum.DNA content is not correlated with chromosome number in these bryophytes, but sperm cell size and cellular complexity are directly related to C‐value. Structural variations in the locomotory apparatus are viewed as evolutionary modifications associated with changes in genomic complexity, with a generalized increase in complexity of the motile assemblage accompanying increases in DNA content. Nuclear DNA values are not as variable in bryophytes as they are in pteridophytes and seed plants. We suggest that in plants producing biflagellated gametes, lower DNA contents afford a selective advantage. Comparisons with plants that produce multiflagellated or pollen‐dispersed sperm indicate operation of a nucleotypic effect in archegoniates with biflagellated sperm. This effect may be on sperm cell functioning, which in turn influences reproductive success.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb15643.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

Foliar spray applications of 40% aqueous methanol were made to sunlit leaves of sour orange trees that had been grown continuously in clear‐plastic‐wall open‐top enclosures maintained out‐of‐doors at Phoenix, Arizona, for over 5.5 years in ambient air of approximately 400μmol mol‐1CO2and in air enriched with CO2to a concentration of approximately 700μmol mol‐1. No unambiguous effects of the methanol applications were detected in net photosynthesis measurements made on foliage in either of the two CO2treatments. The 75% increase in CO2, however, raised the upper‐limiting leaf temperature for positive net photosynthesis by approximately 7 C, which resulted in a 75% enhancement in net photosynthesis at a leaf temperature of 31 C, a 100% enhancement at a leaf temperature of 35 C, and a 200% enhancement at 42 C.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb15644.x

出版商:Wiley    

年代:1995

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11524.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

We studied the response of the pollen grain wall to the passage of materials from the external environment. Pollen grains ofLycopersicon esculentum, a species not previously investigated in similar studies, were used to determine whether the routes of passage through the pollen wall are a characteristic of a given species. We found lanthanum deposits on the cell wall surface, inside microchannels crossing tectum, and in the infratectum. Lanthanum was also seen as a fine precipitate homogenously scattered within the substance of the exine. In the apertural region of the intine, electron‐dense deposits filled the tubulations of the intine oncus, whereas the intine matrix was free of precipitate. In the cytoplasm, precipitate was observed inside small vesicles frequently located near or in contact with the plasmalemma. Our findings were similar to those reported in other species, and were not influenced by the fixative or culture medium used to incorporate the tracer element. We noted a relation between the route of passage and the stage of pollen grain maturation. In less mature grains (midbicellular pollen), electron‐dense deposits were more abundant than in more mature grains, probably because apertural regions were blocked as routes of passage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb15645.x

出版商:Wiley    

年代:1995

数据来源: WILEY