摘要:

The effects of stress on reproduction inClarkia unguiculatawere investigated by monitoring flower number, seed number and seed wt after subjecting plants to drought and heavy fruit loads, and by monitoring seed number after pollinating overage flowers. Fewer main‐stem flowers were produced in drought stressed plants than in non‐stressed plants. Drought stress did not affect overall seed numbers and seed wt in 1981, but did significantly affect seed number and wt in different flower age classes. Overall seed numbers were not affected by drought stress in 1982, but seed wt was significantly lower in plants with stressed ovules. Fewer flowers but more seeds per pollination were produced by plants in which all or ½ the flowers were pollinated than by plants in which ¼ or 1/6 of the flowers were pollinated. Seed wts were lowest in plants with a full fruit load and in fruits produced late in the growth cycle. Seed number was variable but high following pollination of flowers with 1–7 day old stigmas, and much lower in flowers with older stigmas.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08573.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Genetic analysis of isozyme segregation patterns inLayia(Compositae) showed that cytosolic phosphoglucomutase isozymes are encoded by duplicated genes, and that the cytosolic NADP‐dependent isocitrate dehydrogenase isozymes are encoded by duplicated genes in species with haploid chromosome numbers ofn =7 and triplicated genes in those withn= 8. The duplicated genes specifying both isozymes assorted independently in all species tested. An electrophoretic survey of phosphoglucomutase in diploid species representing six additional genera of Madiinae, the subtribe to whichLayiais assigned, revealed thatAchyrachaena, Calycadenia, Hemizonia, Holocarpha, andMadiaall possessed duplicated genes. InLagophylla, one species also had duplicated genes for the isozyme but a second species did not, a loss probably resulting from mutation or chromosomal deletion. The phosphoglucomutase duplication characterizes nearly the entire subtribe and may prove useful to identify phylogenetic relationships between the Madiinae and other subtribes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08574.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Species in the genusSyngoniumgerminate on the ground and mature on the trunks of the trees. These vines consist of relatively unbranched shoots which grow through the forest for considerable distances both horizontally and vertically. In the three species of this study, the shape of the segment, measured as internode diam/length, falls into two distinct classes, leafy and elongate, and varies cyclicly along single shoots. Two cycles are recognized. One cycle occurs in small diam terrestrial shoots in which cycling seems to be controlled by endogenous factors, and occurs with a period of a few tens of segments. The other cycle occurs in shoots of larger diam which climb and descend from trees. In this cycle, alternation between the two forms is controlled by gain or loss of contact with trees, and shoots may remain within a phase of the cycle for hundreds of segments, as long as the substrate does not change.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08575.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Of all the genera of woody bamboos described from America, only three have pseudospikelets—Atractantha, Elytrostachys, andGuadua.The former two have pseudospikelets with an elongated rachilla internode that precedes the floret, making it pedicellate; they also share a type of leaf anatomy that separates them from the latter. The two new genera herein described,CriciumaandEremocaulon, show most similarity to species ofGuadua, both in spikelet morphology and in leaf anatomy. The study of these new taxa has helped to clarify the limits of New World genera with pseudospikelets and strengthened the case for maintainingGuaduaas a genus distinct from its Old World counterpart,Bambusa.We are now able to discern a New World line of bamboos that includesCriciuma, Eremocaulon, andGuadua, separate from an Old World line that includesBambusa, Dendrocalamus, and several other genera.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08576.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

A field survey of plant and flower sex ratio and secondary sex characteristics was made inSilene alba.Female‐biased plant sex ratios were found, as seems typical for the species. Sex ratio distribution correlated with a gradient of soil moisture (with the more moist area having a more female‐biased ratio) and with changes in the density ofSilene(intermediate and higher density areas having greater female bias). The floral sex ratio was significantly female‐biased only at the site that was most female‐biased in terms of plant sex ratio. Otherwise the population of flowers was significantly male‐biased. Male and female plants harvested from the field differed in secondary sexual characteristics. Males had more flowers and invested proportionately more biomass in leaf, but less in root, stem and reproductive tissue than did females. Although both males and females were larger in terms of total dry weight at the moist site, males produced more flowers at the driest (high density) site. Here the female bias in plant sex ratio was intermediate, but the floral sex ratio was significantly male‐biased.A glasshouse experiment was performed in which plants were grown at four densities. Density significantly influenced plant survivorship and the probability of flowering, and increased female bias in the pots, but it did not affect patterns of biomass allocation in flowering plants. Patterns of male and female biomass allocation did not differ in the experiment, except in terms of reproductive allocation (greater in females) and allocation to leaf, greater in males, but only at the lowest density. This work urges caution in interpreting differences between males and females in the field as secondary sex characteristics, since we find such properties to be overlapping under experimental conditions. It supports the idea that males and females of a species may sustain different reproductive output under differing conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08577.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

The feasibility of grouping anther‐derived plants ofSolarium phurejaaccording to ploidy based on their morphological characteristics was studied. Canonical discriminant analysis identified four characteristics (anther length, number of chloroplasts per pair of guard cells, leaf width, corolla width at widest diam) of nine measured as the most effective combination for diagnosing ploidy. Data for these characteristics from two sets of plants were subjected to two clustering techniques, one using the average linkage clustering (UPGMA of the NT‐SYS programs) and the other using centroid sorting (SAS‐Fastclus). Screening of anther‐derived plants by cluster analysis proved to be an efficient means of separating monoploids from the other ploidy levels.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08578.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

As in other hepatics, the young spermatid ofBlasia pusillacontains a well‐developed blepharoplast comprising a four‐layered multilayered structure (MLS) and two overlying dimorphic basal bodies. The asymmetrical spline (S1or upper stratum of the MLS) numbers 20 or 21 microtubules (MTs) at its anterior tip and reduces to eight at the posterior limit of the lamellar strip (LS). Behind this the shank of the spline is five or six tubules in width over most of its length, approximately one revolution of the circumference of the gamete. The three‐microtubule spline aperture underlies the anterior basal body and like those of most hepatics, it is closed at its anterior end. The asymmetrical LS (approx. 2.0 μm in length) is characterized by a right‐hand posterior notch which lies below the spline aperture at the region of the cartwheel configuration of the anterior basal body (ABB). The staggered dimorphic basal bodies overlap for approximately one third of their lengths. Both lie parallel to the long axis of the spline. As in other hepatics, the ABB (1.2 μm in length) is subapical and comprises an anterior hub extension with progressive rearward additions of lateral, dorsal and ventral triplets. Over most of its length (2.1 μm) the longer posterior basal body (PBB) consists of a distinct central hub and three ventral triplets. Transition zones of both basal bodies contain stellate configurations into which the two central axonemal MTs frequently extend. The blepharoplast ofBlasiashows several features in common with leafy, simple thalloid and complex thalloid liverworts. Compared with the few Metzgeriales observed thus far, the LS is less elongate and the basal bodies less staggered. Dimensions of basal body components and spline dimensions, however, are comparable to those of most leafy and thalloid hepatics. Striking similarities with the complex thalloid liverworts include a posterior notch in the LS and a spline aperture three MTs wide.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08579.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Secretory canals, lined with an epithelium, occur in many families, e.g.,Umbelliferae, Compositae.These canals are said to extend continuously through the root and shoot systems and are known, in some cases, to secrete resins, essential oils, etc. InXanthiumthe canals arise schizogenously from cells derived from canal initials. Subsequent divisions lead to a ring of 7–12 epithelial cells surrounding a central cavity. During maturation the epithelium becomes crushed and obliterated. Canals were examined in petioles ofXanthium pensyhanicum(Cocklebur) grown under long day illumination to maintain vegetative growth. The fine structure of the canal and its epithelium was studied by electron microscopy of thin sections cut transverse to the principal axis of petioles from leaves in an early stage of development. The canal proper is delimited by walls of epithelial cells which protrude into a scallop shaped cavity. In comparison to the surrounding parenchyma, the epithelial cells are smaller, cytoplasmically more dense, and less vacuolate. The epithelium contains pleomorphic starch‐free plastids with planar thylakoids frequently stacked into grana; thus, the plastids are presumed photosynthetically active. Mitochondria are abundant and often dense. The cytoplasm is rich in free polysomes, and smooth endoplasmic reticulum predominates over the rough form. Spheroidal granules averaging about 530 nm in diameter are numerous in the epithelium and appear at lower concentration in neighboring cells. Many features of fine structure of the epithelial cells suggest that a high metabolic activity is present in this tissue during this early stage of development. A possible function of the canals is defense against insect predation and animal grazing.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08580.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

The motion induced by wind ofSetaria geniculate(Lam.) Beauv. andAgrostis hiemalis(Walt.) B.S.P. panicles is shown to have harmonic characteristics that can influence pollination. During each cycle of its motion, the panicle ofS. geniculatarepeats a sequence of reorientations to the direction of ambient airflow. This repetition is correlated with a reiteration of airflow patterns through which airborne pollen grains must pass to reach floral surfaces. The panicle decelerates as it moves toward either of the two extreme positions of its oscillatory motion. The decelerations introduce a bias in the time the panicle spends in each of its orientations. This bias generates “preferred orientations” to the direction of ambient airflow which in turn results in biasing the aerodynamics of pollen capture. Similar phenomena are reported for the panicle ofA. hiemalis, although a more complex pattern of oscillatory motion is observed. The reciprocity between the mechanics of oscillatory motion and the aerodynamics of pollen capture is shown to have deterministic properties which may surface above the “noise” produced by other, stochastic features influencing wind pollination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08581.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

A wind and insect exclusion pollination experiment was conducted in a wild population of the cycadZamia pumilaL. in Florida. Cones from which insects but not wind were excluded produced no viable seeds, while cones from which wind but not insects were excluded produced abundant viable seeds. Two beetle species have been identified which may be effecting pollination. Adults and larvae of both beetles are found abundantly on the male cones, and adults of both species and larvae of one species are found occasionally on female cones. Z.pumilaproduces sugar and amino acid‐rich micropyle droplets which may serve as pollinator rewards. Mimicry of resource‐rich male cones by female cones and the use of cones as refuges between mating and feeding bouts may account for beetle movement from male to female cones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08582.x

出版商:Wiley    

年代:1987

数据来源: WILEY