摘要:

Allocation to vegetative growth and sexual reproduction was investigated throughout the growing season in the dioecious sedge,Carex picta, under natural conditions and following experimental manipulations. Measurements taken on unmanipulated plants showed that the sexes did not differ in the total amount of biomass they allocated to either growth or reproduction. The relatively equal investment in reproduction by the two sexes is contrary to other studies, the majority of which show greater investment in reproduction by females. Two features of the reproductive biology ofC. pictamay account for the equal investment: the fruit are relatively inexpensive because they are uniovulate and nonfleshy, and the stamens are relatively expensive becauseC. pictais wind pollinated. In contrast to the lack of differences in the amount of allocation, there were differences between the sexes in the timing of allocation to growth and reproduction: males allocated more to reproduction and less to growth up to the time of flowering, whereas females showed this pattern during the time of fruit maturation. Defoliation and inflorescence removal experiments showed that a trade‐off within plants between growth and reproduction does exist. In addition, the defoliation experiment revealed a difference in the response of the two sexes: defoliated tillers on males showed a reduction in growth, whereas defoliated tillers on females did not. Overall, the data support the idea that differences in the timing of reproductive expenditure are as important as the amount of expenditure in determining many aspects of the life history strategies of the two sexes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15229.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Fossilized flowers of ericalean affinity are reported from the Turanian (ca. 90 MYBP, million years before present) of New Jersey. The fossils are remarkably well preserved and three‐dimensional, and are the oldest known floral remains of Ericales. The series of fossil flower buds, floral fragments, and fruits are not identical to any modern genus of Ericales. The inverted U‐shaped anthers with pseudoterminal awns, and the fluted syncarpous ovary of the fossils suggest affinities with basal Ericaceae, probably near extantEnkianthus, a taxon that also shares monadinous pollen with the fossil. Pollen grains were observed clumped on a stigma in one of the fossil flowers. Fossilized acid‐resistant strands having characteristics, including similar diameter and sculpture pattern, in common with the muri connect pollen grains and, with scanning electron microscopy, appear continuous with the tectum, supporting the interpretation that they are viscin threads. These are the oldest reported fossilized viscin threads, and the only fossilized viscin threads found in situ in flowers. In modern Ericales and Onagraceae, the presence of viscin threads is associated with highly specific plant‐pollinator relationships, raising the possibility that such specific pollinator‐plant relationships had developed by the mid‐Cretaceous. This is consistent with floral characters in these ericalean fossils, the presence of advanced meliponine bees in slightly younger sediments from the same region, and with the morphology and affinities of other fossil flowers from the same sediments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15230.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Vittaria graminifoliagametophytes reproduce asexually by linear six‐celled propagules known as gemmae. It has been shown previously that asymmetric cell division and rhizoid elongation in gemmae are inhibited by millimolar concentrations of Ca+ +. The present paper shows that millimolar Ca+ +delays the onset of cell division at a point prior to mitosis, without affecting the maximal rate of cell division. Ca+ +is most effective in delaying cell division when it is present during the first 24 hours of culture, 2 or 3 days before the initiation of cell division. Millimolar Ca+ +inhibits rhizoid elongation by delaying its onset, while also reducing its maximal rate. Ca+ +is also most effective in delaying rhizoid elongation during the first 24 hours of culture. Culture of gemmae on Ethylglycol‐bis‐(aminoethyl ether)‐N,N,N‘,N‘‐tetraacetic acid‐buffered media shows that the maximum frequency of cell division occurs at pCa 7, while for the initiation of rhizoid elongation, it occurs at pCa 5.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15231.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

The selling rate of hermaphrodites, inbreeding depression, and relative fecundity of females compared to hermaphrodites were estimated for a gynodioecious population ofChionographis japonicavar.kurohimensisto test the models for the evolution of gynodioecy. In spite of the high level of selling of hermaphrodites, significant amounts of inbreeding depression were found in seed germination and seedling growth. In addition, females produced more fertilized ovules than hermaphrodites. Nevertheless, the conditions theoretically required for maintaining gynodioecy were not satisfied even if the combined effect of these two factors was considered. Additional causes for the evolution of gynodioecy, including biparental inbreeding, are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15232.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

The Asian skunk cabbageSymplocarpus renifoliushas an exothermic spadix on which about 100 flowers bloom in very early spring when effective pollinators such as bees and drone flies are inactive. This species is protogynous; female phase and male phase took 6.8 ± SD 5.8 days and 16.7 ± 5.7 days, respectively, with a short transitional phase of bisexuality (2.1 ± 0.9 days). The spadices produced heat 24 hours/day throughout female and bisexual phases, but temperature dropped quickly after the beginning of male phase. Although self‐compatibility was expected from the flower structure, the basipetal flowering, and the absence of effective pollinators, bagging tests demonstrated that they rarely produce seeds without crossing. The spadices were visited by small numbers of invertebrates throughout the flowering season. Of these invertebrates, house flies, rove beetles, and mosquitos were the likeliest pollinators, since they are probably attracted both to the pollen produced in male phase and to the stench or carbon dioxide in female phase. On two female spadices with immature male flowers, we fortuitously collected a rove beetle and a mosquito that carried some pollen grains; these had to have been transported from otherS. renifoliusspadices. This infrequent and ineffective pollination appears to explain why as low as 13% of spadices set seeds in a natural population. We examine alternative hypotheses to explain production of heat in spadices of skunk cabbage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15233.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Male and female individuals of dioecious species often differ in morphology, physiology, growth, and habitat distribution. Where habitat distribution differences have been demonstrated, female plants generally occupy those habitats with greater resource availability (“rich” habitats). Gender‐specific habitat preferences are often presumed to be a consequence of greater resource requirements, per gamete, of female reproduction. Previous work has shown thatPhoradendron juniperinum, a xylem‐tapping dioecious mistletoe that parasitizesJuniperusspecies in western North America, displays the opposite pattern: males are relatively more numerous than females in richer sites (i.e., branches with relatively high light and low evaporative demand within the host tree). We report here differences in host (“site”) quality and gas‐exchange properties between the sexes. To minimize environmental variation, all measurements were made on sunlit foliage between 9:00 a.m. and 2:00 p.m. Males had significantly higher photosynthetic rates (4.0 [SE = 0.2]μmol m‐2sec‐1) than either females (2.9 [0.3]μmol m‐2sec‐1) or nonreproductive individuals (3.0 [0.2]μmol m‐2sec‐1). Female photosynthetic rates were not statistically different from those of nonreproductive individuals. No concomitant differences in stomatal conductance were observed. Gas exchange data were independently confirmed by significant differences in carbon isotope ratio (δ13C). Gender‐related differences were not related to host quality as measured by foliar N, foliarδ13C, or water potential of the host tree. The fate of the additional photosynthate in males is unknown, but we discuss the possibility that carbon costs of reproduction in males have been underestimated in past work.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15234.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

The extent of natural variation among wild typeArabidopsis thalianaL. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32Arabidopsisecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and nonvernalized plants were transplanted into 8‐ (short‐day) and 20‐hour (long‐day) photoperiods in controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15235.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Cones inLibocedrus plumosaare initiated in New Zealand in February (late summer) and continue to develop through winter. The ultimate pair of bracts protrude and continue extension growth while the apex remains flat. Ovules are initiated in two pairs in July on the cone apex (i.e., are axial in origin), alternate with the upper two pairs of bracts. Ovule differentiation proceeds rapidly to the stage of pollination; the cone apex may develop further as a short columella. Soon after ovule initiation an adaxial ligulelike outgrowth of each member of the upper two pairs of bracts is initiated, that of the ultimate pair being broader than that of the lower pair. By intercalary growth of each ligule base an enlarged structure is developed, displacing the bract into a lateral position and forming the four scales that enclose the developing seeds in a valvate manner. Cone and seed maturation follows with seed dispersal in March, approximately 1 year after cone initiation. The results show that there is no morphologically discrete ovuliferous scale, and there is no ontogenetic fusion of discrete separate structures. The vascular system of the scale complex develops after the ovules are initiated and forms a single series of vascular bundles with inversely oriented xylem and phloem; this and other histological changes are the result of the activity of the intercalary growth process and do not relate to primary structures. The results are discussed in relation to existing knowledge of cone development in Cupressaceae, in which axially borne ovules are common.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15236.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Chromosome numbers are now known for 153 species in 21 genera of Lobelioideae (Campanulaceae); this represents almost 13% of the species and 70% of the genera in the subfamily. Numbers reported aren= 6, 7, 8, 9, 10, 11, 12, 13, 14, 19, 21, 35, 70. The subfamily as a whole hasx= 7; the best documented exception isDowningiaand its allies withx= 11. Only four genera show interspecific variation in chromosome number:Downingia(n= 6, 8, 9, 10, 11, 12);Lobelia(n =6, 7, 9, 12, 13, 14, 19, 21);Pralia(n= 6, 7, 13, 14, 21, 35, 70); andSolenopsis(n= 11, 14). Intraspecific variation occurs in 13 species, with as many as four different cytotypes in one species. The herbaceous members of the subfamily as a group are quite variable, showing the entire range of chromosome numbers, including numerous dysploids, but are predominantly diploid. The woody species, by contrast, are much less variable; nearly all of the species are tetraploid, with only a few diploids and hexaploids and no dysploid numbers known. These data support the hypothesis that woodiness is apomorphic within the subfamily. A general trend of higher chromosome numbers at higher latitudes and higher elevations is evident within the subfamily. The chromosome number ofApetahia raiateensis(n= 14) is reported here for the first time, on the basis of a count made about 30 years ago by Peter Raven.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15237.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

We used chloroplast DNA restriction site analysis to test hypotheses of relationships ofSolariumsubgenusPotatoe(including potatoes and pepinos), two otherSolanum, Cyphomandra(the tree tomatoes), andLycopersicon(the tomatoes).CapsicumandDaturawere used as outgroups. The results support two main clades among the taxa we studied: 1)SolanumsubgenusPotatoeandLycopersicon; and 2) otherSolanumandCyphomandra. Within the first clade, the following groups were supported: a) sect.Basarthrumand sect.Anarrhichomenum; b) sect.Etuberosum; c) sect.Petota; d) sect.Juglandifolium, including subsect.Lycopersicoides;and e) the genusLycopersicon. These results, in combination with an analysis of morphological data, advocate the controversial, but previously suggested, treatment ofLycopersiconas congeneric withSolanumin subgenusPotatoe. Thus, the cultivated tomato will be recognized asSolanum lycopersicumL.Solanum chmielewskiiandSolanum lycopersicumvar.cerasiformeare proposed as new combinations;Solanum neorickiiis proposed as a new name forLycopersicon parviflorum. Our data also suggest thatCyphomandrashould be included withinSolanum.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15238.x

出版商:Wiley    

年代:1993

数据来源: WILEY