摘要:

Variation in seed size may produce variation in seedling fitness, but the relationship is not simple. Differences in seed size within and among species may not have the same effects. We examined effects of differences in seed size within and among three species ofSesbania, S. macrocarpa, S. drummondii,andS. vesicaria,on seedling emergence and growth in the greenhouse and the field. Of the three species, the largest‐seeded species,S. vesicaria,produced the largest, longest‐lived seedlings in both the greenhouse and the field. Even though plant size differed, annualS. macrocarpaproduced the same seed mass as annualS. vesicariain the greenhouse. Within‐species effects were less clear. In the greenhouse,S. vesicariaseedlings grown from large seeds remained largest until maturity, but the other species did not exhibit this effect. Some persistent within‐species effects of seed size differences on height were observed in the field in 1981, but not in 1980, suggesting that field conditions increase the importance of seed size differences. Unscarified S.drummondiiseeds germinated before seeds of the two annual species. Within species, larger seeds of the annuals and smaller seeds of the perennial germinated first. Differences among the species in the importance of seed size to seedling fitness may allow the species to have different patterns of regulation of reproduction in response to stress.Sesbania vesicariashowed the largest within‐species effects of seed size and has the lowest plasticity in seed size, suggesting that patterns of plasticity have been selected such that the most important component of yield varies least.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12063.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Efforts to introduce Dutch Elm Disease resistance into the American elm (Ulmus americanaL.) through breeding with Asian elms has been hampered by sexual incompatibility. Controlled pollinations ofUlmus americanaand the Siberian elm (Ulmus pumilaL.) were studied in detail to gain insight into the nature of this incompatibility. Microscopic observations revealed that germination and early pollen tube growth were inhibited on the stigmatic surface following both intra‐ and interspecific incompatible pollinations. Both qualitative and quantitative differences in pollen inhibition on the stigmatic surface indicated that the inhibition may involve the action of an inhibitory substance. Detailed observations on callose deposition indicated that this β‐1,3 glucose polymer may implement the inhibition.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12064.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The microsporogenous tissue of at least some species of all 17 genera of Onagraceae is divided by transverse septa composed only of tapetum or of both tapetum and parenchyma. The presence of these septa apparently constitutes a distinctive characteristic of the family. InCalylophussect.Salpingia, Gaura, Clarkia, Heterogaura,and two unrelated species ofLudwigia,the septa are transverse and mostly parenchymatous. InHauyaandCalylophussect.Calylophus,similar transverse septa together with vertical ones divide the sporogenous tissue into many small spheroidal or ellipsoidal packets. The condition in which occasional tapetal septa divide the sporogenous tissue is clearly the ancestral one in Onagraceae. Polysporangiate anthers divided by parenchymatous septa have evolved independently at least twice each in the branches leading toLudwigiaand to all other members of the family, for a total of no less than four times. Based on this feature and the unique pattern of histogenesis of their integuments,Hauya(despite its retention of many plesiomorphic features),Calylophus,andGauramay well be directly related to one another.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12065.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Arisaema triphyllumis a gender‐labile woodland herb in which sex expression is correlated with the abundance of stored resources. Larger plants are female or monoecious, smaller ones are male. Among females larger plants produce more flowers, fruits and seeds, and the rate of successful fruit and seed formation is greater for plants of greater ht and corm diam. Average seed wt is greater in larger plants. Seed number per fruit and average seed wt per fruit taper towards the top of the infructescence. Pollinator limitation and resource supply may both contribute to the regulation of yield; their effects can be interpreted sequentially.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12066.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Seedling density on permanent plots at five sites was monitored for the first four summers following the deposition of 4.5 to 15 cm of tephra from the 1980 eruption of Mount St. Helens. Because the old‐growth forests at the sites were not destroyed by the volcanic eruption, the plots were under a normal tree canopy. Almost no seedlings established in 1980. By 1983 tree seedling density exceeded 35 m−‐2at all sites.Tsuga heterophyllaseedlings were most common, withAbies amabilisseedlings next in abundance. A dense layer of small trees may develop on the tephra and long‐term forest dynamics could be affected. There was no successful invasion by species not already present in the stands. Seedlings of some forest herbs, especiallyTiarella trifoliata,were common, but many other common forest species produced none. It is still problematical if or when these species will return to areas of the forest from which they were extirpated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12067.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Seed weight varies significantly within and among fruits of wild radish (Raphanus raphanistrum). To determine sources of this variation, we studied fertilization and seed development following controlled pollinations. Within fruits, central ovules were fertilized prior to distal ovules and attained greater seed size. Ninety‐seven percent of the variation in mean seed wt per fruit was explained by an analysis of variance incorporating parental effects, pollination date, and the number of seeds per fruit. We document strong maternal effects on the number of ovules per ovary, the number of fertilized ovules per ovary, the number of seeds per fruit, and mean individual seed wt per fruit. Across females, pollen donor had a slight but significant effect on seed wt; no paternal effects on fertilization rate, zygote number, or seed number per fruit were detected. Within females, with one exception, pollen donor had no significant effect on these components of seed development. Stronger maternal main effects may be due to donor x recipient interactions, cytoplasmic factors, the genetic inequity within triploid endosperm, and/or strict maternal control over resource allocation. The large maternal effects relative to paternal effects may limit the rate at which natural selection acts on paternal traits expressed prior to seed maturation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12068.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

BothAvicennia germinans(black mangrove) andRhizophora mangle(red mangrove) are commonly found in anaerobic substrate. Black mangrove roots create oxidized rhizospheres substantially larger than those described for other plant species. When air cannot enter the root system through the pneumatophores, the rhizospheres become as reduced as nearby un vegetated soil. The presence of red mangrove, in contrast, appears to have no effect on the oxidation state of surrounding anaerobic soils. It is likely that these data help to explain the distributions of both species in intertidal associations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12069.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Plants ofClarkia unguiculatawith moderate numbers of long hairs on the ovary and calyx were selected for relative “hairlessness” through 11 generations. Inbreeding depression, manifested as a high degree of sterility, necessitated co‐selection for fertility. The proportion of fertile plants among families ranged from 0–50% in the 5th selected generation and increased to a range of 53–100% in the 10th selected generation. At the same time, the mean number of hairs on the ovary decreased from a range of 0.0–1.1 to a range of 0.0–0.2; and the mean number of hairs per sepal from 0.5–16.0 to 0.1–2.2. The percentage of plants per family with no hairs on the ovaryandno hairs on the calyx increased from a range of 0–63 in the 5th selected generation to a range of 4–88 in the 10th selected generation. Nonselected progenies have long hairs on both ovary (mean 10–17) and sepals (mean 46–50) in all plants. The demonstrated response to selection has important implications regarding catastrophic selecion and the evolution ofClarkiaspecies in marginal habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12070.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Plants ofAcomastylis rossiiandBistorta viviparawere treated in the field with artificial acid mists prepared with sulfuric acid, nitric acid, or mixtures of equal parts of these at pH 2.5, 3.5, or 4.5. Highly significant reductions in flower production inA. rossiiwere noted with sulfuric acid treatments at pH 2.5 and in bulblet production inB. viviparawith nitric acid at pH 2.5 and 3.5, with sulfuric acid at pH 3.5, and with nitric‐sulfuric acid mixtures at all pH's. These results apparently relate to the growth forms of the plants, which cause pooling of the acid solutions at their bases. Significant increases in flowering and in leaf number were noted forB. viviparatreated with sulfuric acid, possibly as a promotive effect of sulfate. No effects on vegetative growth were noted inA. rossii.The germinability of seeds (A. rossii) and bulblets (B. vivipara) also was not affected. Differential sensitivity of plant species to artificial acid mist implies that acid precipitation could cause a change in species composition of Colorado alpine plant communities.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12071.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Cytology of four species ofAlliumfrom western Canada was studied. Three species viz:A. acuminatum2n= 14,A. cernuum2n= 14, andA. schoenoprasum2n= 16 were found to be diploids with normal meiosis. Some populations ofA. cernuumandA. schoenoprasumcontained a high number of B‐chromosomes. Diploid (2n= 14) and tetraploid (2n= 28) populations were encountered inA. textile.While the diploid meiosis was regular, the tetraploids showed 1–5 quadrivalents at metaphase I, suggesting their possible autoploid origin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb12072.x

出版商:Wiley    

年代:1986

数据来源: WILEY