摘要:

Tobacco plants derived from herbicide (paraquat)‐resistant cell lines and from wild type (non‐resistant) cell lines were self‐pollinated and crossed with sexually‐derived wild type plants. Analysis of the seed germination frequencies from these crosses indicated that seed viability and thus the ability of tissue culture‐derived plants to intercross with sexually derived plants was reduced. Partial reduction was observed when tissue culture‐derived plants were the female parent. Significant reduction in ability to intercross was observed when tissue culture‐derived plants were the male parent. Self pollinations of tissue culture‐derived plants and crosses between tissue culture‐derived plants, both wild type and mutant, did not show the presence of a crossing barrier. The crossing barrier (reduction of seed viability) is due to either: 1) failure of a fertilized ovule to undergo embryonic development, or 2) failure of pollen to fertilize ovules. It is apparently not due to in viable pollen. A possible explanation of the crossing barrier is that genetic changes accumulate as a result of the tissue culture process which reduces the ability of tissue culture‐derived plants to cross with sexually‐derived plants. Since tissue culture‐derived plants are able to intercross with each other and produce viable seed, the genetic changes would be similar in all of our tissue culture‐derived lines, regardless of mutant or wild type origin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12044.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Two cytological races ofAsterwhich morphologically resembleA. ascendensbut differ from it in chromosome number are found in the Transverse and Peninsular ranges of southern California. One of these races is relatively common, can usually be separated morphologically fromA. ascendens,and has a somatic chromosome number of 36; it corresponds to the endemic speciesA. bernardinus.The other race is rare and localized, is morphologically almost indistinguishable fromA. ascendens,and has a somatic chromosome number of 42. The chromosome numbers and karyotypes of the two races suggest that they originated through backcrosses ofA. ascendens(x= 13) to its respective parent taxa,A. falcatus(x = 5) andA. occidentalis(x= 8).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12045.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The occurrence of the Crassulacean acid metabolism (CAM) was studied in four epiphytic species of the Gesneriaceae: two neotropical species,Codonanthe crassifoliaandColumnea linearis,and two paleotropical species,Aeschynanthus pulcherandSaintpaulia ionantha.Gas exchange parameters, enzymology, and leaf anatomy, including mesophyll succulence and relative percent of the mesophyll volume occupied by airspace, were studied for each species.Codonanthe crassifoliawas the only species to show nocturnal CO2uptake and a diurnal organic acid fluctuation. According to these results,Codonanthe crassifoliashows CAM‐cycling under well‐watered conditions and when subjected to drought, it switches to CAM‐idling. Other characteristics, such as leaf anatomy, mesophyll succulence, and PEP carboxylase and NADP malic enzyme activity, indicate attributes of the CAM pathway. All other species tested showed C3photosynthesis. The most C3‐like species isColumnea linearis,according to the criteria tested in this investigation. The other two species show mesophyll succulence and relative percent of the leaf volume occupied by airspace within the CAM range, but no other characters of the CAM pathway. The leaf structure of certain genera of the Gesneriaceae and of the genusPeperomiain the Piperaceae are similar, both having an upper succulent, multiple epidermis, a medium palisade of one or a few cell layers, and a lower, succulent spongy parenchyma not too unlike CAM photosynthetic tissue. We report ecophysiological similarities between these two distantly related families. Thus, the occurrence of CAM‐cycling may be more common among epiphytic species than is currently known.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12046.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The basis for the negative correlation between seed number and seed size was experimentally investigated in a natural population ofClintonia borealis.Clones of this species vary significantly in estimated self‐compatibility (ratio of seed set with selfing to that with outcrossing) and this appears to affect the number and size of seeds set in individual flowers of each. Clones estimated to be largely self‐compatible set more seeds per flower than incompatible ones under natural pollination. However, naturally pollinated flowers of self‐compatible clones set smaller seeds than those of incompatible clones, and the significance of the negative relationship between seed number and size in individual flowers was removed by holding variation due to compatibility constant. Supplementing resources per flower (by reducing the number of fruits competing for resources per stem) significantly increased total seed mass but had no effect on the negative relationship between seed number per flower and seed size. In contrast, supplementing cross pollination did not significantly influence total seed mass per flower but changed the relationship between seed number and size to positive, regardless of resource level. In other words, with plentiful cross pollination maternal genets capable of setting more seeds per flower also produced heavier ones. Thus, evidence is provided that the balance between seed number and seed size in this population is regulated by the interaction of maternal self‐compatibility with natural pollination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12047.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Morphological and aerodynamic traits affecting mean potential dispersal distance are quantified for wind‐dispersed diaspores of tree species on Barro Colorado Island, Panama. The sample includes 34 species in 16 families and represents six aerodynamic groups. Mass and area (maximum cross section) each vary over six orders of magnitude among the species. In contrast, wing‐loading, defined as weight divided by area, varies over only one order of magnitude, as does the rate of descent. While the regression of rate of descent on the square root of wing‐loading is significant overall, the slopes vary significantly among five aerodynamic groups. At comparable wing‐loading values, diaspores of fluffy kapok fall faster than four other aerodynamic groups and rolling autogyros fall faster than non‐rolling autogyros. Assuming the diaspores are released from their typical tree height and experience a mean windspeed of 1.75 m sec−‐1, the expected mean dispersal distance varies among the 34 species from 22 to 194 m. Rate of descent is weakly correlated with shade tolerance of seedlings for a subset of 18 species; rate of descent is more strongly correlated with the log of dry mass of seed for all 34 species. Given these wide differences in dispersal potential, any generalizations about tropical trees that use wind dispersal are of dubious value.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12048.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Tree species composition and density were monitored in closed oak‐hickory forest and forest‐prairie edge for a period of five years after a prescribed burn. In the closed forest, tree stem density declined markedly following the burn. Tree basal area and density decreased from 17.5 m2/ha and 630 trees/ha in the preburn sample to 12.0 m2/ha and 310 trees/ha five years later. In contrast, on the forest‐prairie edge, tree basal area and density increased slightly during the same time period from 3.0 m2/ha and 117 trees/ha to 5.2 m2/ha and 172 trees/ha. Our data suggest that closed canopy forests in fire susceptible areas accumulate fuels to levels that encourage fires of sufficient intensity to destabilize forest systems and convert them to open forests or savannahs. Conversely, on the forest‐prairie edge, amounts and patterns of fuel accumulation, and species response to burning, are such that fire can be considered to be a factor promoting stability.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12049.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Three previously unknown algal forms are preserved as carbonaceous residue and impressions in basal St. Louis Formation (Valmeyeran Series) of Jersey County, Ill. On the basis of morphologic similarities the algae are considered to belong to Rhodophyta and Phaeophyta. The algae are associated with conularia. The algae and conularia probably lived in shallow marine water on the eastern flank of the Ozark Dome and southern margin of the Illinois Basin. This region would have been at approximately 20 south latitude during the Visean.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12050.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Amphicarpaea bracteata,an annual legume common in woodland communities in the eastern United States, produces three distinct types of flower: subterranean cleistogamous (SCL), aerial cleistogamous (ACL), and aerial chasmogamous (ACH). We sought to quantitatively describe the growth and reproduction of four diverseA. bracteatapopulations in an effort to explain the adaptive significance of this species’ variable reproductive modes. Virtually all plants develop 1 to 3 SCL seeds on subterranean cotyledonary shoots, starting in late July. Larger plants produce additional SCL seeds later from the tips of axillary shoots which bury. Seeds produced by SCL flowers are large (39 to 134 mg), have restricted dispersal, lack dormancy, have high germination(x¯≖95%), and produce relatively vigorous seedlings. ACL flowers develop from early August through plant senescence in early October, while ACH flowers appear in a pulse in late August. The number of each aerial flower type was positively correlated with plant size. The ACL flowers take significantly less time to develop mature fruits than do ACH flowers. Both aerial seeds are smaller than the subterranean (mean weights: ACL 12.1, ACH 8.7 mg), have lower germination (ACL 20.2%, ACH 15.3%), appear relatively resistant to environmental extremes, and have the potential for more widespread dispersal. Plants derived from subterranean seeds are much larger than plants derived from aerial seeds, which makes them more likely to produce axillary SCL and aerial seeds. Only larger plants derived from subterranean seeds and growing in favored sites produce ACH flowers. This imposes an alternation of selfing with outcrossing generations. This pattern of reproductive behavior inA. bracteatais similar to that found in several other amphicarpic species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12051.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

TillandsiaL. Subg.Phytarrhiza(Visiani) Baker (Bromeliaceae) is a distinctive group of about 35 epiphytic species. These exhibit a range of habits from xeric to mesic. The evolutionary relationships of the contrasting adaptations need to be established here as well as in the subfamily as a whole. Relations between the subgenus and other tillandsioids are problematical and phylogenetic reconstruction of its member‐species would be facilitated by identification of Phytarrhiza's relative (sister taxon) sharing the same most recent common ancestor withPhytarrhiza.This paper examines the two most likely sister taxa, Subg.Pseudo‐CatopsisBaker and Subg.Diaphoranthema(Beer) Baker.Diaphoranthemais rejected as sister taxon. The accepted evolutionary tree, rooted byPseudo‐Catopsis,indicates that most habital evolutionary changes inPhytarrhizahave been between mesic and semi‐mesic forms and from mesic to xeric forms. Methods developed for testing specific evolutionary hypotheses are broadly applicable.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12052.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

In an examination of the generic boundaries ofBrachiaria,ten anthecial patterns are recognized for the genus, eight for the first time. A smooth surface is proposed as the basic pattern from which the ornate patterns are produced. The laminar abaxial epidermis displays panicoid microcharacters. Foliar anatomy is the type associated with the C4, PEP‐carboxykinase photosynthetic pathway. However, no species groups are discernable and the variation withinBrachiariaappears to be continuous.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12053.x

出版商:Wiley    

年代:1986

数据来源: WILEY