摘要:

The evolutionary origin of the coleorhiza of species of Poaceae is unclear. Thezrp3 gene, which codes for a protein of an as yet unknown function, is expressed in the roots of maize early in development. The sequence ofzrp3 is similar to the sequences of three other genes isolated from dicot species. The pattern of accumulation of ZRP3 mRNA was examined in embryos of maize. No ZRP3 mRNA can be detected in the dry seeds; however, 1.5 d after inhibition, ZRP3 mRNA accumulated in both the roots and the coleorhiza of the embryo but not in other regions of the seed. In the roots, ZRP3 mRNA accumulates specifically in the cortical ground meristem and the pro‐pith tissues. In the coleorhiza, ZRP3 mRNA accumulates in the parenchymal cells but not in the epidermal cells, thus distinguishing two tissue types in this organ. The accumulation of ZRP3 mRNA in the coleorhiza as well as in the root is molecular evidence consistent with the homology of these two organs.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11577.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

Thickening of perianth segments, loss of original nonchlorophyllous pigments, and chlorophyll production occur inPhalaenopsisspecies of sectionZebrinaePfitzer as postpollination phenomena. This also occurs in several hybrids of members of this section withPhalaenopsisspecies whose perianth wilts following pollination. The observed dilution of pigments in hybrids containing regreening and wilting genomes indicates involvement of dominant nuclear genes. Increases in chlorophyll levels are most pronounced within 40 d following pollination and increase moderately or level off after 80 d. Seed capsules and perianths of selfed species, which had not dehisced, turned yellowish 160 d after pollination and had reduced levels of chlorophylla, but not chlorophyllb.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11578.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

To understand the genetic regulation of vegetative to reproductive transition in higher plants, further characterization of theArabidopsismutantembryonic flower1, emf1, was conducted. Using three flowering symptoms, we showed thatemf1mutants could only grow reproductive and not rosette shoots under five different growth conditions. The mutant embryos did not produce the typical tunica–corpus shoot apical structures at the heart‐, torpedo‐, and mature stages. The divergent shoot apical development during mutant and wild‐type embryogenesis indicated that the wild‐typeEMF1gene was expressed in early embryogenesis. Mutations in theEMF1gene affected the embryonic shoot apical development and caused the germinating embryo and regenerating callus to grow inflorescence, instead of rosette, shoots. Our results support the hypothesis that theEMF1gene regulates the switch between vegetative and reproductive growth inArabidopsis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11579.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

We investigated the use of a monoclonal antibody (MAb 238) to the soybean Bowman‐Birk inhibitor (BBI) to verify and understand the intergenomic relationships among the wild perennialGlycinespecies. Competitive enzyme linked immunosorbent assay and western blot screening studies revealed that the accessions of B‐genome (G. latifolia, G. microphylla, andG. tabacina, 2n= 40) and C‐genome (G. curvataandG. cyrtoloba) species did not contain the MAb 238 crossreactive proteins (BBI‐nulls). By contrast, all the A‐genome (G. argyrea, G. canescens, G. clandestina, and G.latrobeana), E‐genome (G.tomentella, 2n= 38), and F‐genome (G. falcata) species, G.arenaria(genome unknown), and the polyploid (2n= 78,80)G. tomentellaaccessions were BBI‐positive. The D‐genomeG. tomentella(2n= 40) and tetraploid G.tabacina(2n= 80) contained both BBI‐null and BBI‐positive type accessions. Among the recently described species, G.hirticaulis(2n= 40),G. lactovirens, and G.pindanicacontained the MAb 238 crossreactive proteins whileG. albicansdid not.Glycine hirticaulis, G. pindanica, and G.tomentella(2n= 38) displayed highly similar MAb 238 crossreactive isoelectric focusing banding patterns, indicating that they are genomically close to each other.Glycine hirticauliswas found to have both diploid (2n= 40) and tetraploid (2n= 80) cytotypes. We demonstrated that the MAb 238 was specific to the trypsin inhibitor domain of the BBI. The MAb 238 clearly reflected all the previously established relationships in the genusGlycine, validating its use as a genome marker.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11580.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

We discuss the errors in common approximations of the volume flow rate for laminar flow through conduits with noncircular transverse sections. Before calculating flow rates, ideal geometric shapes are chosen to represent the noncircular transverse sections. The Hagen–Poiseuille equation used with hydraulic diameter underestimates the volume flow rate for laminar flow through conduits even with such ideal shapes. Correction factors that have been proposed for the Hagen–Poiseuille equation also lead to underestimates of the volume flow rate for those shapes. The exact solutions are sometimes difficult to attain, but rates calculated using the exact solutions for the ideal shapes may be as much as five times higher than the approximated rates for common transversely elongated shapes. Either the exact solutions or the approximations may be used to calculate volume flow rates through the xylem of plants. Both of these methods actually approximate flow through the original conduits because the shapes used are approximations of the conduits’ transverse sections. We recommend using the exact solutions whenever possible; they should be closer to the real solution than other approximations. We give tables of correction factors for use in the cases where calculating volume flow rate from the approximate solution, the Hagen–Poiseuille equation, is more feasible. Obtaining theoretical volume flow rates that are larger than previously thought highlights the need to clarify the causes of differences between the theoretical rates and the smaller measured volume flow rates in plant xylem.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11581.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

The study of phenotypic plasticity, the ability of a given genotype to express different phenotypes as environments change, is becoming a central focus of ecological genetics and evolutionary theory. To help address the most pressing questions about plasticity (its genetic control, ecological relevance, and macroevolutionary consequences) we advocate the use ofArabidopsis thaliana(and eventually other related species of the same genus) as a model system. In this study we present experimental data concerning: (a) the extent of reaction norm variation to two levels of nutrients in a worldwide collection of 26A. thalianapopulations; and (b) the existence of multivariate associations among key phenotypic characters, and their reaction to changes in the environment. We found significant among‐population genetic variation for eight of the nine traits measured, as well as plasticity in four traits. Five traits showed significant differences in genetic variation between the two environments. The multivariate association of the nine traits defines four major groups of covarying characters, each of which may be plastic or not, depending on the particular population. The use of populations that can be easily obtained by any researcher, because they are part of a worldwide collection, implies that it will be easy to build on our results during future investigations of phenotypic plasticity in this species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11582.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

The evolution of selfing vs. outbreeding has been of major interest to plant population biology. The independent historic introductions of self‐compatible and self‐incompatible genotypes of cacao in Trinidad have allowed us to study the selection acting upon an unnatural breeding system polymorphism. Field observations of an abandoned cacao plantation indicate that the self‐incompatible phenotype has slightly increased in frequency within a single generation. The self‐compatible trees produced significantly less flowers but still set more pods than did the self‐incompatible trees, although compatibility types did not differ in tree size or mature seed production. Greenhouse observations suggest that the apparent failure of self‐compatibility to increase in the population is related to inbreeding depression resulting from selfing, expressed as reduced seedling establishment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11583.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

The lifespan of an individual flower is often affected by pollination success. Species differ regarding whether male function (pollen removal), female function (pollen deposition), or both trigger floral senescence. We studied senescence in the singleflowered, deceptive orchidCalypso bulbosaby manipulating the degree of male and female reproductive success. We found that deposition of any amount of pollen resulted in dramatic changes in shape and color within 4 d, whereas unmanipulated flowers and those that had had pollinia removed remained unchanged for 8‐11 d after treatment. Selection may favor the reproductive function that is less easily satisfied as the trigger for senescence, because a flower that senesces after accomplishment of this function is likely to have already succeeded at the more easily satisfied one. Deceptive (i.e., rewardless) flowers are more likely to satisfy male than female function since the latter requires that a pollinator be fooled twice, first to pick up pollen and second to deposit it. A survey of naturally pollinatedCalypsoshowed that male function, pollinium removal, was more likely to occur than female function, deposition (95% vs. 66% of visited flowers); thus floral senescence inCalypsois triggered by achievement of the function less likely to succeed. Studies of senescence triggers in species in which female function is more likely to be achieved than male are necessary to further test this hypothesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11584.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

We used path analysis to ask whether leaf position or leaf light level was a better predictor of within‐plant variation in leaf nitrogen concentration in five species of rain forest pioneer trees (Cecropia obtusifolia, Ficus insipida, Heliocarpus appendiculatus, Piper auritum, andUrera caracasana) from the Los Tuxtlas Biological Station, Veracruz, Mexico. Three hundred seventy‐five leaves on 28 plants of the five species were analyzed for leaf nitrogen concentration, leaf mass per area, and leaf light interception at different positions (= nodes) along a shoot. Mean values of leaf nitrogen concentration ranged from 0.697 to 0.993 g/m2in the five species, and varied by as much as 2.24 g/m2among leaves on individual plants. Leaf position on the shoot explained significantly more of the within‐plant variation in leaf nitrogen concentration than did leaf light level in four of the five species:Cecropia obtusifolia, Heliocarpus appendiculatus, Piper auritum(branch leaves only), andUrera caracasana.However, individual species differed considerably in the patterns of nitrogen allocation and leaf mass per area among leaves on a shoot. These results suggest that leaf nitrogen deployment in these plants is, in part, developmentally constrained and related to the predictability of canopy light distribution associated with plant growth form.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11585.x

出版商:Wiley    

年代:1995

数据来源: WILEY

摘要:

Stable hybrid zones are believed to occur because gene dispersal is opposed by selection, but the nature of this selection remains unclear. The dynamic equilibrium model postulates that hybridization disrupts coadapted gene complexes, leading to alterations in development and subsequent hybrid unfitness. Alternatively, the bounded hybrid superiority model assumes that selection is due to exogenous factors. Here, we examine the developmental instability of sagebrush across a narrow hybrid zone. The results show no difference among the parental and hybrid taxa for the majority of comparisons examined. When significant differences in developmental instability were observed, one of the parental taxa (mountain big sagebrush) was typically the least developmentally stable. Hybrids were found to be the least developmentally stable for only two of the 28 comparisons studied. Interestingly, for some comparisons, hybrids were themostdevelopmentallystable.These results contradict predictions of the dynamic equilibrium model. The sagebrush hybrid zone does not appear to be maintained by endogenous selection, as there is little indication that development is disrupted by hybridization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1995.tb11586.x

出版商:Wiley    

年代:1995

数据来源: WILEY