摘要:

The implications of leaf size, leaf display, and crown size for whole‐plant light interception were investigated inGeonoma cuneataandAsterogyne martiana,two understory palm species native to Central American rain forests. Adults ofA. martianahad longer leaves, more leaves per plant, and greater total leaf area thanG. cuneataadults. Geometric measurements within whole crowns were used to calculate light interception efficiency, a leaf‐based measure of the proportion of total incident light that is intercepted by a crown. Light interception efficiency was higher in adultG. cuneatathan in adultA. martiana;seedlings of the two species did not differ significantly in light interception efficiency. Decreased efficiency of adultA. martianacrowns was largely due to an increased proportion of pendent leaves. Compared toG. cuneata,adults ofA. martianahad greater light interception capacity (the product of light interception efficiency and total leaf area), but they also had higher biomass costs of light interception. Lower biomass costs of light interception in adultG. cuneataenable this species to exploit successfully the most deeply shaded microsites in the rain forest understory.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08412.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Long‐styled (pin) and short‐styled (thrum) plants in populations ofMitchella repensfrom North Carolina and New York displayed strongly clumped spatial dispersion. This distribution pattern results from the tendency of these prostrate perennials to spread by production of trailing stems with adventitious roots. Both morphs, in both populations, exhibited natural fruit set exceeding 86%. This percentage was not increased by hand‐pollination. Although the number of ovules per pair of ovaries was fixed at eight in each morph, numbers of seeds per fruit in naturally pollinated flowers differed significantly between pins (4.3) and thrums (6.4) in the North Carolina population. In the New York population, no significant differences were found (pins had 5.0 seeds per fruit; thrums, 4.4). Artificial pollinations in both populations showed low seed set in intramorph cross‐pollinations as compared with intermorph crosses. The flowers ofM. repenswere visited by native species ofBombus,which visited many flowers in each patch of plants. These insects moved frequently from patch to patch, effecting intermorph cross‐pollination and maintaining high levels of seed set. Movement among patches may be promoted by the dispersion of nectar rewards, with flowers about to open or just opened providing maximum amounts of nectar. Calculations of functional gender suggested that in the North Carolina population, thrums contributed more than 75% of the genes transmitted by ovule production. This contrasts strongly with previous studies of unequal sexual contributions in distylous taxa, which have demonstrated greater female contributions by pins. In the New York population, however, nearly equal contributions by pins and thrums through pollen and ovule production occurred, a situation similar to that found in most distylous species. This appears to be the first demonstration of variation in functional gender between populations of a single species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08413.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Controlled pollinations, followed by germination studies of seeds resulting from self‐ and cross‐pollination, were carried out using plants from 12 populations of nine species ofAphelandra(Acanthaceae), a genus of neotropical shrubs and herbs. These results are combined with data from field studies of flower morphology, phenology, and pollinator relationships to estimate breeding system of each species. All species have floral morphological traits that prevent autogamy. Plants from five populations of five species experience low levels of geitonogamous pollen transfer; they produce few flowers daily and are pollinated by traplining hummingbirds. ExceptingA. storkii,these plants are fully self‐compatible (SC), and seeds from selfing are as viable as crossed seeds.Aphelandra storkiiis partially self‐incompatible (SI) and produces seeds from selfing that tend to germinate less successfully than crossed seeds. Plants from the remaining populations are profusely flowering shrubs, and even those pollinated by traplining hummingbirds should experience higher levels of geitonogamy.Aphelandra deppeanais pollinated by territorial hummingbirds, which should further increase the incidence of geitonogamy. All shrub species are partially SI, and two species (A. leonardiiandA. sinclairiana) show significant reduced germination of selfed vs. crossed seeds. The breeding system of these species is thus modified by postpollination factors that favor the formation and maturation of outcrossed seeds. It is suggested thatAphelandraspecies, like other herbs and shrubs of tropical forest understory, possess a combination of breeding system traits that promote outcrossing but do not exclude geitonogamy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08414.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

F1hybrids obtained from crosses between the rubber‐bearing species,Parthenium argentatumGray (commonly known as guayule), andP. schottiiGreenman ex Millspaugh and Chase, a nonrubber‐producing species from southern Mexico, were morphologically variable. They were generally intermediate between the two species with respect to leaf size, head size, number of disk florets per head, and the length of the peduncles. Like the parental species, the hybrids had 2n= 36 chromosomes. They averaged 14.56 bivalents, 3.92 univalents, 0.56 trivalents, and 0.32 quadrivalents, indicating a high degree of homeology between the genomes of the two species. The observation of one quadrivalent at diakinesis in 32% of the PMCs and the frequent occurrence of a bridge accompanied by a fragment at late anaphase I of the F, hybrids suggested that the two species differ in a reciprocal translocation and a paracentric inversion. The ease of hybridization, the partial fertility of the hybrids, and their high degree of chromosome pairing indicate thatP. schottiiandP. argentatumare closely related in spite of their distinct morphological features and geographical distributions. This close relationship provides an opportunity to transfer genes fromP. schottiito guayule for desirable characteristics, such as high biomass production and resistance toVerticillium dahliaeKleb, by means of interspecific hybridization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08415.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Moisture applied to dry seeds ofEuphorbia supinaRaf. caused helices embedded in the seed coat to elongate. The helices consist initially of tightly coiled strands that loosen when moistened. The helices can repeatedly elongate and contract, but their configuration and expandability gradually changes as the strands coalesce to form thin plates. With prolonged exposure to moisture and drying, the plates, in turn, coalesce into an amorphous layer that covers the seed. Periodic Acid‐Schiff test produced red coloration, which indicates the helices contain polysaccharides, probably mucilage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08416.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The breeding system ofSpachea membranacea(Malpighiaceae), an understory tropical rain forest tree, was studied on Barro Colorado Island in central Panama. Two types of trees were found, those with hermaphroditic flowers and those with female flowers. Crossing experiments indicated that morphological hermaphrodites normally function as males but may be induced to set fruit if emasculated prior to cross‐pollination. Thus, although morphologically gynodioecious,S. membranaceais functionally dioecious. This is the first experimental evidence for functional dioecism in the Malpighiaceae. The proportions of hermaphrodites (functional males) in the three populations examined were 44.7% (N= 47), 60.0% (N= 10), and 87.5% (N= 17). The distribution of hermaphrodites and females in size classes was quite similar, suggesting that sexual expression is not influenced by the age of the individual. Flowers are visited and presumably pollinated primarily by bees of the generaParatetrapedia(Anthophoridae) andTrigona(Apidae).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08417.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

We studied the reproductive ecology ofClintonia borealis,a clonal understory species, in eastern Ontario. Flowers are protogynous and require insect pollination for outcrossing and maximum seed set. Most pollination is done by nectar‐gathering bumble bees. We recorded pollen deposition and flowering patterns in 1983. Flowering lasted for about 10 days in mid‐June. Stigmatic pollen loads were lowest at the onset of blooming, reflecting the scarcity of male‐phase flowers. Pollination increased significantly by peak bloom and subsequently remained high. However, since bees fly mostly between neighboring stems, much of the pollen transferred may have been geitonogamous. In 1983, seed set per flower was not increased by supplementing pollination or by reducing the number of fruits competing for resources per stem. Rather, flowers set more seeds (14%) only if both treatments were performed simultaneously. Seed size was increased by 25% when competitive fruits were removed and by 5% more when pollen was added under the removal treatment. Further work in 1984 showed that pollination effects may be related to changes in pollen source. Selfed flowers set fewer and smaller seeds than outcrossed ones when screened from insects and hand pollinated. Outcrossing distance had little effect on seed set or seed size. Thus, inC. borealisseed number and seed size are limited by a balance between maternal resource availability and the amount of outcrossing provided by pollinators.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08418.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Megasporogenesis and megagametogenesis were examined inGlycine maxwith light, fluorescence, and electron microscopy. Megasporogenesis results in a linear tetrad of four megaspores. Megagametophyte development is of thePolygonumtype, with the functional chalazal megaspore undergoing three successive mitotic divisions to produce an eight‐nucleate, seven‐celled mature megagametophyte. The central cell becomes packed with starch. At fertilization, the antipodals are degenerate, the polar nuclei have fused, starch is diminished, and the egg occupies most of the micropylar portion of the megagametophyte. Several pollen tubes were occasionally observed at each micropyle, yet only one was involved in fertilization. Pollen tube entry occurs through a slightly reduced, viable synergid cell. Endosperm development precedes embryo growth. These results describing normal development allow important comparison with genetic mutants of soybean that affect female fertility.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08419.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Starch content was qualitatively assessed for pollen of 79 of the 111 currently recognized genera of the family Araceae—one of three monocot families known to exhibit both starchy and starchless pollen. Although 73% of the genera investigated had exclusively starchy pollen, character correlation suggests that starchless pollen is the primitive type for the family Araceae, as well as for monocots in general. Pollen starch content is a highly conservative character at the generic level in Araceae; only a single genus (Schismatoglottis) clearly exhibits both character states. The distribution of starchy pollen among aroid genera is consistent with what have here been termedBakers' Starch Laws.Aroid pollen below a certain critical diameter—17‐25 μm—is almost invariably starchless. Larger pollen is nearly always starchy, except where insect pollinators may use pollen nutritionally. There is strong evidence that the trend from starchless to starchy pollen in Araceae is reversible, according to the constraints imposed by the aforementioned factors.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08420.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

In both male and female flowers ofH. morsus‐ranaethe primordia of the floral appendages appear in an acropetal succession consisting of alternating trimerous whorls. In the male flower a whorl of sepals is followed by a whorl of petals, three whorls of stamens, and a whorl of filamentous staminodes. The mature androecial arrangement therefore consists of two antisepalous stamen whorls, an antipetalous whorl of stamens, and antipetalous staminodes. Shortly before anthesis, basal meristematic upgrowth between filaments of adjacent whorls produces paired stamens, joining Whorls 1 and 3, and Whorl 2 with the staminodial whorl. A central domelike structure develops between the closely appressed filaments of the inner stamen and staminodial whorl, giving the structure a lobed appearance. After petal inception in the female flower a whorl of antisepalous staminodes develop, each of which may bifurcate to form a pair of staminodes. During staminode development a girdling primordium arises by upgrowth at the periphery of the floral apex. The girdling primordium rapidly forms six gynoecial primordia, which then go on to produce six free styles with bifid stigmas. Intercalary meristem activity, below the point of floral appendage attachment, leads to the production of a syncarpous inferior ovary with six parietal placentae. The styles and carpels remain open along their ventral sutures. During the final stages of female floral development, several hundred ovules develop along the carpel walls, and three nectaries develop dorsally and basally on the three antipetalous styles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08421.x

出版商:Wiley    

年代:1985

数据来源: WILEY