摘要:

Normally, starch (sugars) and minerals are redistributed from the leaves to the pods during monocarpic senescence in maturing soybean plants. Petiole phloem destruction (steam girdling), which blocked this redistribution by interrupting export through the petiole, altered the foliar senescence pattern producing a distinctive interveinal yellowing with green areas along the veins on pod‐bearing plants. This suggests that blockage of the petiole phloem may cause nutrients to accumulate in the green zones along the leaf veins instead of being redistributed to the pods. In the leaves of untreated plants, starch showed the same distribution pattern as chlorophyll; however, starch was preserved in yellow areas as well as the green zones of the steam‐girdled leaves. Mineral analyses of the veinal and interveinal zones of treated leaves and controls showed that the veinal green zones and interveinal yellowing in treated plants were not respectively enriched and depleted in minerals corresponding to a redistribution of minerals within the leaves. Depodding also blocked leaf yellowing, net mineral redistribution and starch breakdown. Thus, the pods are able to induce chlorophyll breakdown without net mineral redistribution or starch loss in leaves with petiole phloem destruction. This shows that chlorophyll breakdown is not obligatorily coupled with mineral redistribution or starch breakdown.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10882.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

A selectedPinus taedaL. tree was rapidly and permanently water‐stressed by severing and sealing the bole and observed daily for seven wk and then weekly for six months. Insects were captured before and during treatment from the stressed and adjacent control trees. Tissue samples were extracted at selected intervals for comparison of the stressed and control trees. Drying of the crown of the stressed tree commenced immediately. By the tenth day the previous yrs' needle clusters were red and dropping from the tree while the current yr's needle clusters remained green and did not fall. By the eleventh day beads of resin, predominantly α‐ andβ‐pinene, formed and dripped from the abscission scars of the youngest needle clusters of the previous yr. At this time and for several days thereafter, insects were attracted to the stressed tree. Microscopy of abscission sites of the stressed and control trees shows that the sites where resin flowed had incomplete abscission layers, lysigenous collapse of adjacent cortical cells to form a cavity that coalesced the resin ducts associated with the needle cluster, and had mechanically ruptured the tissue connections so that resin normally contained within the duct system was released to the exterior of the tree. Volatilizedα‐pinene is attractive to the insects associated with pines. Failure of abscission in the stressed tree leading to abnormal resin release is thus proposed as a means by which insects are attracted to stressed trees.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10883.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The density and distribution of stomates inCarex aquatilisWahl. in the Pacific Northwest were examined using epidermal peels of samples of leaves from natural populations, from greenhouse‐grown transplants and from seedling families grown under controlled conditions. These were compared to stomatal distributions of populations in eastern North America.Populations ofCarex aquatilisWahl. form 2 groups based on the distribution and density of stomates.Carex aquatilisvar.dives(Holm) Kükenthal is epistomatic, with adaxial stomatal densities of 28.7–48.5/0.1 mm2. TheC. aquatilisvar.aquatilisis amphistomatic, with adaxial stomatal densities of 8.1–22.2/0.1 mm2and abaxial densities of 11.3–24.5/0.1 mm2in the Pacific Northwest. Total stomatal frequencies are similar in both groups. Stomatal distribution and densities are here shown to not vary significantly within populations and appear to be genetically determined, as shown by progeny tests and growth of seedlings under uniform and experimental conditions. Stomatal distribution inCarex aquatilisappears to be adaptive, and intraspecific variation provides a system for determining the adaptive significance of differences in stomatal patterns.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10884.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Chromosome numbers are reported for ten taxa inSphaeralceasectionFendlerianae(Malvaceae). New ploidy levels are reported for six taxa, with one species not previously reported, and extensive polyploidy at all taxonomic levels is documented. The geographic and taxonomic distribution of polyploids suggests that polyploidy arose many times in the taxa ofSphaeralcea. Sphaeralcea fendlerivar.venusta, S. polychroma, andS. wrightiipopulations have yielded exclusively tetraploid counts. Tetraploidy is correlated with taxa having lavender petals. Polyploidy has also allowed the taxa to expand their distributions without resulting in speciation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10885.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Patterns of floral nectar production and standing crop were measured in four populations of the herbaceous perennial plant speciesPolemonium foliosissimum.Contrary to prediction (Pleasants, 1983), individual flowers in this mass‐flowering species were found to produce equivalent nectar volumes every day of their lives. Alternative methods of increasing the reward variability presented to pollinators are evaluated forP. foliosissimumand the relationship between that variability and risk‐aversive foraging by pollinators is discussed. Significant spatial and temporal variability in rate of nectar production was found. Populations separated by approximately 200 m exhibited different rates. Nectar production declined significantly as a function of time of the flowering season in two populations but not in a third. In spite of such variability, individual plants showed consistency in production both within a single blooming season and across successive seasons. Because of the variability found in the present study, care should be taken to design appropriate sampling protocols in future nectar studies. Patterns of standing nectar crop were consistent with those expected if pollinators were using an area‐restricted searching pattern.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10886.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The reproductive ecology ofJeffersonia diphylla(L.) Pers. (Berberidaceae) was investigated by studying its breeding system, ovule production, seed set, seed dispersal by ants and seed predation by rodents. This species flowers early in the spring and is facultatively autogamous. In a typical year fruit and seed set is high (90%), however, freezing temperatures from late spring frosts in 1983 and 1985 resulted in low fruit set (7% and 20%, respectively), and reduced seed set in those flowers that produced fruit. No differences in seed set between selfed and outcrossed flowers were observed over a two‐yr period (1983–84). Ovule number per capsule increased with plant size as measured by leaf number. Seed set and seed wt were unaffected by leaf number unless leaves were removed after flowering was initiated.Jeffersonia diphyllais myrmecochorous. Ants removed seeds faster when seeds were placed in areas whereJ. diphyllaplants were absent, suggesting that dispersal withinJ. diphyllapopulations is ant limited. Moreover, fresh (1 day old) seeds were removed by ants faster than 3 day old seeds. Seed predation by rodents prior to dehiscence from capsules is heavy in large populations (85–90%), and apparently negligible in small populations. Predation of seeds that are released from capsules is heavy (approx. 66%), particularly at night. Overall, seed predators consume about 96% of the seed crop in well established populations, but probably much less in small young populations. Hence, seedling recruitment is likely to be higher in small populations, whereas ramet production from rhizomes is the primary mode of propagation in large ones. The evolution of autogamy, early flowering, and myrmecochory are discussed in light of the results of this study.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10887.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The morphological boundaries betweenArbutus xalapensisandA. glandulosaare diffuse. Many individuals share traits of both species. The character most commonly used to distinguish the species is the presence of glandular hairs inA. glandulosa.Comparisons in the field of the number of colonies and level of defoliation byEucheira socialis(Lepidoptera, Pieridae), anArbutus‐specific herbivore, showed that the damage is greater for glabrous than pilose trees and greater for pilose than glandular trees. Additionally, the geographic distribution of glandular trees is strongly correlated with that ofE. socialiswhile that of non‐glandular trees is not. We suggest that the glandular and non‐glandular forms could belong to one single polymorphic species in which the glandular characteristic is maintained by differential herbivory.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10888.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The two C4Panicumspecies examined differ in C4acid decarboxylation type and in developmental origin of bundle sheaths in major veins of their leaf blades. InPanicum effusumR.Br. (NAD‐malic enzyme type) both mesophyll (PCA) and chlorenchymatous bundle sheath (PCR) cells are derived from ground meristem. In contrast, inPanicum bulbosumH.B.K. (NADP‐malic enzyme type), bundle sheath cells are derived from procambium, while mesophyll develops from ground meristem. To test the hypothesis that the developmental divergence of bundle sheath and mesophyll cells would occur earlier when these two tissues had different ontogenetic origins (inP. bulbosum) than when these tissues had the same origin (inP. effusum), the development of major veins in each species was investigated. We measured cell length and cross sectional area, plastid and mitochondrial number, plastid area, vacuole area fraction, wall thickness and fraction adjacent to intercellular space using direct and digitizer measurements of transmission electron micrographs of leaf cross sections of successive developmental stages. Many of the statistically significant changes in the structural parameters measured occurred late in development of both species. The magnitude of developmental change inP. effusumPCR cells was sometimes more dramatic, viz. changes in cell and PCR plastid area, and in mitochondrion number per cell. However, earlier divergence of PCR and PCA length and volume, and wall fraction adjacent to intercellular space inP. bulbosumthan inP. effusumindicates that ontogenetic origin of PCR cells from procambium could determine the timing of at least some developmental events.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10889.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

The pollination process in loblolly pine has been examined over several years, both in the field (seed orchards) and experimentally on greenhouse‐grown material. Female strobili are receptive to pollination for periods of a wk or more. Initially, background pollen from outside the seed orchard is the main source of pollen but as peak receptivity approaches, pollen from the stand itself predominates especially in older orchards. Consequently, strobili can receive pollen both from outside the orchard as well as from within. The pollen lands on the micropylar horns where it is transferred through the micropyle onto the nucellus by either rainfall or the pollen drop, whichever comes first. Since the pollen drop does not occur until the latter part of the receptive period, rainfall is the most likely transfer agent and pollen flotation is vital if rain occurs. Early arriving pollen does not appear to have an advantage over later arriving pollen for uptake onto the nucellus, even if rain follows the first pollination immediately. Therefore, total pollination of the strobilus can result from both distant and nearby pollen sources.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10890.x

出版商:Wiley    

年代:1986

数据来源: WILEY

摘要:

Field observations, chromosome counts, flavonoid chemistry, breeding system data, hybridization experiments, and a quantitative analysis of twelve morphological features combine to show that the North and Central American populations ofB. pilosasensu Sherff actually include three distinct species:B. odorata(n= 12),B. alba(n= 24), andB. pilosa(n =36). All these taxa are square‐stemmed, white‐rayed or discoid annuals with linear, obcompressed‐quadrangulate achenes, but each species can be distinguished morphologically by differences in ray length and width, in outer phyllary length, width and shape and chemically by differences in the chalcones accumulated in their leaves. New combinations are proposed and two varieties,B. odoratavar.oaxacensisandB. odoratavar.chilpancingensis, are described as new. Descriptions, distribution maps, synonymies, and a key to all taxa are provided.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1986.tb10891.x

出版商:Wiley    

年代:1986

数据来源: WILEY