摘要:

Pods and seeds of field‐collectedBaptisia lanceolalaplants were analyzed to partition seed weight and seed packaging trait variance among and within plants and to detect relationships between these traits. Packaging traits studied were: pod weight, seed weight per pod, number of seeds per pod, mean weight of seeds per pod, proportion seed weight of total pod weight, and pod weight per seed. Significant among‐plant variation was found for seed weight and all packaging traits. Within plants, positive correlations were found between number of seeds per pod and pod dry weight and between the proportion seed weight of total pod weight and number of seeds per pod. Pod weight per seed was negatively correlated with number of seeds per pod. Most plants had a negative correlation between mean seed weight and number of seeds per pod. When compared with an equality of slopes test, slopes of regressions of the above pairs of traits were found to differ among plants. Among plants, the same relationships were found, except for the latter two traits, which were not correlated. These within‐plant patterns may represent constraints on seed weight variance imposed by the seed package. This view is supported by a positive correlation between packaging trait variance and seed weight variance. Packaging‐related constraints could have an effect on seed weight in this and other species. If these phenotypic constraints have a genetic basis, then selection on seed packaging could change seed weight in a way different from that which might be predicted by considering seed weight alone.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15288.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

A new record of a fossil Monterey pine (Pinus radiataD. Don) is recorded from rocks of the Plio‐Pleistocene age, southern California, and the affinities of other presumed fossil closed‐cone pines are revised. This has led to the recognition of two new pine species,Pinus storeyanaAxelrod of subsect.OocarpaeandPinus verdianaAxelrod of subsect. Ponderosae. Geologic evidence indicates that forerunners of the present California and Mexican species ofOocarpaewere in proximity in Mexico during the Miocene. They were isolated following opening of the Gulf of California, the northward movement of Baja and Alta California on the San Andreas fault system, and the spread of desert climate. New populations ofPinus radiatadeveloped during the Pliocene (5–2 million years) and later as environmental diversity increased. This also enabledPinus remoralaMason andP. muricataD. Don, which the fossil record suggests were distinct into the Late Pleistocene, to hybridize in the new topographic‐climatic Holocene environments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15289.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Seed dormancy inSpartina alterniflorawas studied with regard to: 1) the specific site of the dormancy mechanism, and 2) the influence of three growth‐regulating substances: gibberellic acid, fusicoccin, and abscisic acid. The site of the mechanism was determined by assessing the germinability of surgically altered dormant seeds. Effects of the growth substances were determined by assessing the germinability of seeds incubated in their presence. Results revealed that dormancy could be broken surgically by altering the scutellum or chemically by applying fusicoccin. Dormancy could be restored by abscisic acid in the former case but not the latter. It is concluded that the dormancy mechanism is located in the scutellum, that it consists of at least two sequential steps, and that it involves a leachable chemical inhibitor.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15290.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Several workers have suggested that the rarity of androdioecy (the presence of males and hermaphrodites in a breeding population) in nature is due to the large fitness gain required by male plants in order to be maintained by selection. As part of an ongoing investigation of this hypothesis, we tested the effects of selfing on fitness in functionally androdioecious populations ofDatisca glomerata.We compared progeny from self‐fertilizations, cross‐fertilizations with pollen from male plants only, cross‐fertilizations with pollen from hermaphrodite plants only, and open‐pollinated flowers for several measures of progeny fitness including seed weight, germination rate, and seedling weight. Significant inbreeding depression was observed for androdioecious populations ofD. glomeratafor both seed and seedling weights. However, no significant differences were observed across treatments for seed germination percentages. The observation of significant levels of inbreeding depression in this study, combined with prior evidence of threefold greater pollen production by males, may at least partially account for the large fitness increase required by males to be maintained by selection.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15291.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

To determine the effects of soil nitrogen on pollen production, pollen size, and pollen performance, two cultivars of zucchini (Cucurbita pepo) were grown under two nitrogen regimes in an experimental garden. The two cultivars were true breeding for alternative alleles for a one gene trait, ovary color. The soil nitrogen treatment had a significant effect on most measures of reproductive output through the female function. The nitrogen treatment did not affect the number of staminate flowers per plant but did have an effect on the number of pollen grains per staminate flower and the mean pollen grain size. A pollen mixture experiment revealed that pollen produced by plants in the high nitrogen treatment sired significantly more seeds than pollen from low nitrogen plants. Moreover, we found that the high nitrogen pollen sired even a greater percentage of seeds in the region of the fruit (ovary) previously shown to be fertilized by the fastest growing pollen tubes. Thus, the difference in the number of seeds sired by pollen from the two nitrogen treatments is due to differences in pollen performance. We conclude that spatial heterogeneity in soil nitrogen can influence the paternity of seeds in a plant population.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15292.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Green dragon (Arisaema dracontium; Araceae) is a perennial woodland herb capable of switching gender from year to year. Small flowering plants produce only male flowers but when larger they produce male and female flowers simultaneously. Distinct male and monoecious phenotypes (referred to hereafter as plants) share a single underlying cosexual genotype. Four populations in southern Louisiana were sampled to determine frequencies and size distributions of male and monoecious plants, and to determine the relationship of plant size with male and female flower production in monoecious plants. Male plants were significantly smaller than monoecious plants and made up 34%–78% of flowering plants within populations. Flower number (average = 120) was weakly positively correlated with size. Monoecious plants produced an average of 169 flowers (90 female) and had 100% fruit set, with individual berries containing an average of 2.5 ovules and 1.3 filled seeds. Male flower number was negatively correlated, and female flower number positively correlated, with basal stem diameter. Extrapolation of regression slopes suggested that green dragon should become completely female at a size 20% larger than the largest plant observed in this study. A simple model of inflorescence development is presented to illustrate how the reproductive system of green dragon is related to that of jack‐in‐the‐pulpit (A. tnphyllum), which exhibits a more distinct switch between male and female phenotypes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15293.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

To date, reports of paedomorphosis at the whole plant or shoot level have been loosely based on whole plant form or on the sequence of leaf shapes produced along the shoot (heteroblasty). However, interpreting the significance of heterochrony in the evolutionary loss or gain of heteroblasty based on mature leaf forms assumes that all leaves with the same shape arose through very similar modes of organogenesis. This study examines this assumption in two subspecies ofCucurbita argyrosperma,one that is wild and heteroblastic and a second that is cultivated and not markedly heteroblastic. All leaves of the cultivar are visually similar to early leaves of the wild subspecies. The cultivar is considered to be the progenitor of the wild subspecies. Scanning electron microscopy and allometry of developing leaves showed that at early nodal positions along the primary shoot, leaf development in both subspecies was similar. At later nodal positions, very young leaves of both subspecies were more similar to each other than to leaves at earlier nodal positions within the same plant at the same stage of development. This early similarity was masked in the mature shapes of later leaves due to subsequent differences in allometric growth. Thus a simple hypothesis of paedomorphosis in which the early leaf form in the progenitor is simply reiterated at later nodal positions in the cultivar is not supported by patterns of leaf development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15294.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

The relationship between shape variation in the transitional series of leaves and in adult leaves was examined in seedlings of seven morphs ofBegonia dregeiusing several quantitative methods of shape analysis. There is variation in the shape of adult leaves among individuals as well as in juvenile leaves within individuals inB. dregei.As an individual grows, there is a gradual transition in leaf shape from the symmetrical, oval, smooth‐margined leaves through a series of more than ten transitional leaves to a stable adult leaf shape. There appear to be two basic patterns to the acquisition of adult traits. Traits that differ among morphs are acquired gradually throughout the entire transitional series while those that are similar among morphs are acquired by about leaf 5 and remain stable through the later juvenile leaves. There is no identity of leaf shape between the earlier leaves of some morphs and the later leaves of others. Evolutionary diversification in adult leaf morphology in this species is not related to simple changes in ontogeny of the whole plant.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15295.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

The flowers of a previously undescribed recessive mutant of tomato,green pistillate,show strong and consistent homeotic transformation of petals to sepals in whorl two and of stamens to carpels in whorl three. The phenotype at early and later stages is compared with wild type by scanning electron microscopy. Wild type and mutant show no difference in the pattern or timing of third whorl organ initiation, as shown by allometric analysis of scanning electron micrographs of early stages. This confirms that the mechanisms governing organ identity are distinct from those governing the positions and numbers of organs initiated; the former can be altered without changes in the latter. Mutant and wild type organs are compared by allometric analysis of dimensions of flowers dissected throughout development. The sepaloid petals (whorl 2) and the carpelloid stamens (whorl 3) in the mutant elongate at relative rates normal for the wild type organ of the whorls they occupy. This suggests that some aspects of organ growth, such as elongation rate, may also be independent of mechanisms governing organ identity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15296.x

出版商:Wiley    

年代:1993

数据来源: WILEY

摘要:

Members of the speciesAstragalus cymbicarposform chasmogamous and cleistogamous flowers, as well as a large variety of intermediate floral types. Bivariate allometry and Gould's clock models were used to investigate the possible heterochronic evolution of the cleistogamous flower from the chasmogamous flower. In three of the whorls analyzed (pistil, stamens, and corolla) comparison of chasmogamous, pseudocleistogamous, and cleistogamous flowers revealed a progressive “juvenilization” of the adult form. This paedomorphic morphology proved to be partly the result of a process of progenesis, also evident in acceleration of sexual maturity. The retardation of shape with respect to size in these three whorls suggests, however, the existence of a heterochronic process other than progenesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1993.tb15297.x

出版商:Wiley    

年代:1993

数据来源: WILEY