摘要:

Cryptogam‐covered, sandy soils of the Big Sand Mound prairie in southeastern Iowa are significantly more aggregated than bare soils. Soil particles covered by moss are intertwined by rhizoids, whereas cyanobacteria and lichen fungal hyphae adhere to the particles and glue them together. Lichen‐covered samples that were tested and oven dried, then retested 2 yr later, retain their aggregation, indicating that the aggregating material is stable even after the death of the fungus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08433.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The nectar‐sugar compositions of 338 individuals from 27 populations in two subspecies ofIpomopsis longiflorafrom Arizona, New Mexico, Texas, and Chihuahua were determined by high‐performance liquid chromatography. Mean sucrose compositions of populations ranged from 73.2% to 91.9%, and the standard deviations ranged from 1.9% to 9.1%. Pairs and aggregates of populations were statistically compared. The nectar‐sugar compositions of the two subspecies were significantly different as aggregates. Subspeciesaustralisaveraged 9.5% fructose, 7.9% glucose, and 82.6% sucrose while subspecieslongifloraaveraged 7.8% fructose, 5.7% glucose, and 86.5% sucrose. Each subspecies was found to have two groups of populations. Groups of higher sucrose populations were found along the contact zone of the subspecies; away from the contact zone both subspecies had groups of lower sucrose populations. The data show that significant variability exists in this biochemical character, and the pattern of variation is clearly related to the geographic distribution of the populations. The genetic and selective mechanisms involved are unknown.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08434.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Photosynthetic pigments and several structural characteristics were measured in leaves ofAndropogon gerardiifrom tallgrass prairie populations in an unburned, low‐irradiance site and a burned, high‐irradiance site to determine if these species displayed sun/shade differences similar to those documented in forest species. Early in the growing season, leaves ofA. gerardiiin the low‐irradiance, unburned site had significantly lower stomatal density, pore length, and conductance, as well as specific leaf mass and thickness than leaves from the high‐irradiance, burned site. Moreover, the chlorophylla:bratio, carotenoid content, and bundle sheath‐vascular complex area were significantly lower, but chlorophyll content (mass/mass) was greater in leaves in unburned vs. burned sites. These differences are consistent with sun/shade adaptations reported for forest understory plants and may contribute to the low productivity ofA. gerardiiin unburned tallgrass prairie.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08435.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Little information is available on the distribution of ions in seeds of halophytes. Seeds of two halophytes,Salicornia pacificavar.utahensis(Tidestrom) Munz, a desert salt playa type, andAtriplex canescens(Pursh) Nutt., a desert shrub, were analyzed by energy dispersive X‐ray microanalysis. The relative ion concentration in three regions, the seed coat, endosperm, and embryo, were determined. The total relative concentration of elements was higher in seeds ofS. pacificavar.utahensisas compared toA. canescens.The seed coats ofS. pacificavar.utahensiscontained the highest counts of sodium, chlorine, potassium, and calcium, whereas the embryo and endorsperm were both high in phosophorus. InA. canescens,sodium and chlorine were very low in all three tissues. The embryo contained the major amount of phosphorus, although potassium was high in both the seed coat and the embryo. These results support the concept of ion compartmentalization in the seeds of these two halophytes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08436.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The DNA content of the apical cell and various other cells in the roots ofAzolla filiculoideswas determined by two‐wavelength cytospectrophotometry. DNA content decreased markedly with increasing age of the apical cell; there was a similar but less pronounced trend in the other cell populations studied. These findings suggest the possibility of DNA amplification in very young roots with rapidly dividing cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08437.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Seedlings ofDesmodium paniculatumderived from different seed sizes differed in heteroblastic development. The transition from juvenile to adult leaves took place at the fourth node in seedlings derived from larger seeds and at the fifth or sixth node in those derived from smaller ones. Cotyledon removal had no effect on this condition, but growth under reduced irradiance delayed the formation of adult leaves in seedlings from larger seeds. Simple and compound leaves had similar unit area photosynthetic rates and stomatal conductance values, but compound leaves had a 30% higher total area. The earlier production of adult leaves would thus give seedlings from larger seeds an advantage in terms of total carbon gain.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08438.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The breeding system, flowering display, and fruiting pattern ofCalochortus leichtliniiHook. (Liliaceae) was studied in the eastern Sierra Nevada. This species is capable of both autogamy and insect‐mediated outcrossing. Either of these two means of pollination alone could affect full seed set; the populations studied were not pollination limited in 1983. Most individuals produced two flowers but set only one fruit. Flowers are not selectively matured on the basis of the quantity or purported quality of the pollen they receive; the first flower to open was matured in all experiments. Nonfruiting flowers have at least three potentially important reproductive functions: disseminating pollen, allowing plants to produce more seeds in response to an abundance of soil moisture, and setting seeds if the first flower fails to develop fruit.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08439.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

An experiment was conducted to test whether metal tolerance expressed in pollen would provide a competitive advantage during pollen tube growth and fertilization. Copper or zinc was introduced into the pistil by growing metal tolerant plants ofSilene dioicaorMimulus guttatusin a nutrient solution to which metals were added. Flowers from treated and control plants were pollinated with either metal tolerant or metal sensitive pollen. The rate of pollen tube growth, the number of seeds set, and the number of viable seeds produced were measured. In general, no effects were found on the rates of pollen tube growth. However, the number of fertilizations and viable seeds were affected. When toxic metals were present, the relative success of pollen from the nontolerant parent was reduced.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08440.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

A selection experiment was undertaken to test if metal tolerance expressed in pollen was determined by the pollen genotype, and if selection for metal tolerance could be effective during pollen development in the anther. Heterozygous metal tolerant plants ofSilene dioicaandMimulus guttatuswere cloned and grown either in the absence or presence of toxic concentrations of zinc or copper. These metals entered the flowers in potentially toxic amounts. The percent viable pollen decreased when compared to control plants, and the remaining pollen had a different pattern of germination in the presence of metals. In addition, the proportion of tolerant progeny from test crosses to metal sensitive plants increased significantly if pollen came from treated clones. Thus, selection appeared to be effective during pollen development, and metal tolerance in pollen significantly influenced by the pollen genome.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08441.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

It has been suggested that one of the selective advantages of ant dispersal is the burial of seeds in ant nests where predators such as small rodents cannot find them. The elaiosomes ofCorydalis aurea(Fumariaceae) are extremely attractive to ants, which assiduously gather the seeds and take them to nests. However, seed production commonly exceeds the gathering capacity of ants so that seeds accumulate beneath the parent plants. In spite of this, no signs of rodent predation are evident. Experiments with a major seed predator, the deer mousePeromyscus maniculatus,show that when given the choice of seeds with and without elaiosomes, the mice consume significantly more seeds without elaiosomes. This remains true whether or not the intact seeds bear fresh, moist elaiosomes or dry, withered ones. Our experiments strongly suggest that the elaiosome has a dual function, the attraction of the ant seed dispersers and the repulsion of seed predators.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08442.x

出版商:Wiley    

年代:1985

数据来源: WILEY