摘要:

The stigma ofPennisetum americanum(L.) Leeke is of the dry type. Receptive surfaces of papillae are covered by an extracuticular proteinaceous secretion that has esterase activity. Permeability mapping of an intact stigma indicates that the papillate tips of trichome cells are especially penetrable. Numerous discontinuities of the cuticle probably allow passage of surface secretions and of water for pollen hydration. Comparison of pellicle and intracellular proteins by native polyacrylamide gel electrophoresis and analytical electrofocusing showed them to be different. One particular fraction that had esterase activity was a glycoprotein with a molecular weight of 180,000–200,000 daltons and an isoelectric focusing point of 7.5–8.0. This protein was a major component of the pellicle and may play a nonselective role in pollen capture.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11277.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Tetraploid tobacco plants (Nicotiana tabacum) derived from cultured cell lines (TC) are partially cross‐incompatible with their diploid progenitors (C). C × TC crosses (TC‐derived tetraploids as the pollen parent) yield only 2% viable seed. The remaining seeds are normal size but lack an embryo (apoembryonic seeds). Apoembryonic seeds do not occur in the reciprocal TC × C crosses. Sections of ovules from C × TC crosses revealed that an embryo formed but that embryo growth slowed at 5 days postpollination and that by the 12th day following pollination, the embryo had disappeared although the ovule continued to develop. Endosperm degeneration occurred concurrently with embryo death. Culturing ovules from C × TC crosses has increased the yield of F1plants from 2% to as much as 25% indicating that embryo rescue is possible. Surviving F1plants from TC × C crosses have close to triploid chromosome numbers and are fertile.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11278.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The inflorescence ofFagusis generally considered to be a determinate one, i.e., an axillary dichasium, in contrast to those of most genera in the family, which are indeterminate, dichasial, or simple catkins. To understand the relationship between the two types, ontogenetic development of the inflorescence ofFagus crenatawas investigated. The early developmental stages are similar in both the male and the female inflorescences. At first, the inflorescence is oval‐shaped, then a swelling forms at the distal side of it. Subsequently, another swelling forms at the proximal side. The more or less conspicuous residual part of the primary inflorescence axis remains between the two swellings. The inflorescence becomes heart‐shaped and the first flower forms at the summit of each swelling. Subsequently, higher‐ordered flowers form dichasially in the male inflorescence, and the cupule valves differentiate in the female one. This organogenetic manner suggests that the inflorescence ofFagusis an indeterminate one, consisting of two dichasia arranged alternately on the primary axis. The scale leaves surrounding the inflorescence were also given a new interpretation. They were considered to be stipules of the bracts, because sometimes they constitute a continuous structure, together with an inconspicuous swelling between them. A proliferous‐type monstrous cupule was interpreted as supporting evidence for the hypothesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11279.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

A study of flavonoids occurring within a heterocyanic population ofTrillium sessilewas made to determine the chemical basis of a common floral color polymorphism in this species. In the study population, three floral color phenotypes (red, pink, yellow) are determined primarily by the presence or absence of anthocyanin compounds in the petal tissue, and secondarily by quantitative differences in the concentration of several flavonol glycosides. Petals of red phenotypes contain both cyanidin 3‐arabinoside and 3‐diarabinoside, petals of pink phenotypes contain only cyanidin 3‐arabinoside, and petals of yellow phenotypes lack cyanidin entirely. Quercetin 3‐0‐glucoside, quercetin 3‐0‐arabinoglucoside, quercetin 3–0‐arabinogalactoside, and quercetin 3‐0‐arabinogalactosyl, 7‐0‐glucoside occur in petals of all three phenotypes but differ in relative amounts. Petals of the red phenotype have mostly 3‐0‐biosides, but lesser amounts of both quercetin 3‐0‐glucoside and the 3,7‐0‐triglycoside. Petals of the pink phenotype contain relatively equal amounts of quercetin mono‐, di‐, and triglycosides. Petals of the yellow phenotypes contain mostly quercetin 3,7‐0‐triglycosides, and less mono‐ and di‐glycosides. Small amounts of a quercetin tetraglycoside were detected in petals of both yellow and pink phenotypes, but not in red phenotypes. The enhancement of quercetin polyglycoside biosynthesis in yellow petal phenotypes is attributed to the shunting of dihydroflavonol precursors to synthesis of quercetin compounds when their conversion to anthocyanins is blocked genetically.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11280.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Year‐to‐year variation in phenotypic gender in the monoecious cucurbit,Apodanthera undulataGray was investigated. Small plants produce no flowers. Larger plants produce only staminate flowers (“male” plants), while a somewhat greater threshold size is necessary for pistillate flower production (cosexual plants). Approximately 85% of the plants that bloomed did not change gender group between years. Two measures of phenotypic gender were used: prospective femaleness, a measure standardized to the population floral ratio, and morphological femaleness, an unstandardized measure. Femaleness of cosexes between years was positively correlated;rvalues were somewhat greater when using morphological femaleness values. Plants that opened only staminate flowers one year were likely to open only staminate flowers the next year. Similarly, cosexes were likely to be cosexes again the following year, with similar femaleness values. Beyond the threshold size for pistillate flower production, plant size was not correlated with femaleness. These patterns suggest that all plants are male until they reach a certain size and that plants in their cosexual phase may have an intrinsic femaleness tendency due to either genotype or microsite effects.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11281.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Deviations from Mendelian ratios are frequently treated as an intrinsic property of individuals, independent of the environment. We tested whether the environment of the parents could alter patterns of inheritance in the wild radish,Raphanus sativus.We demonstrated the genetic basis of 12 isozyme loci by controlled pollinations of unstressed plants. The frequency of deviant segregation detected was not different than that expected by chance. Controlled pollinations among stressed plants showed over 3 times as much deviant segregation as the unstressed controls. No genetic correlates of segregation bias were detected. Linkage was assessed for 64 of the 66 pairs of loci. Two linkage groups were detected, one involving four loci (PGM2–ACO–ACP–LAP), the other involving a single pair (EST‐PRX). The second linkage group is apparently associated with a locus or tightly linked loci which may segregate for “balanced” lethals on the same chromosome. Deviant segregation did not appear to act primarily by selection on a particular gamete. Postzygotic selection was the probable source of at least some of the aberrant segregation. Because no particular allele was favored in such situations, selection is apparently operating on alleles at linked loci rather than on the allozyme loci per se. Data from other studies on wild radish support the suggestion that postzygotic selection might be an important influence on progeny segregation ratios. Because wild radishes often encounter a variety of stresses in the field, in this species, aberrant segregation may be common under natural conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11282.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Stem elongation and leaf orientation inLilium longiflorumThunb. were influenced more by the difference (DIF) between day temperature (DT) and night temperature (NT) than absolute DT or NT from 14 to 30 C. Plant height and internode length increased 129 and 382%, respectively, as DIF (DT‐NT) increased from –16 to 16 C as compared to only 15 and 58% when either DT or NT was increased from 14 to 30 C, respectively. Leaf orientation, defined as the angle between a line perpendicular to the stem and the line from the leaf base to the leaf tip, increased 43° (leaves became more upright) as DIF increased from –16 to 16 C. In contrast to plant height, internode length, and leaf orientation, leaf and flower length were influenced more by absolute temperature than DIF. Leaf and flower length decreased 32 and 14%, respectively, as NT increased from 14 to 30 C. DT had little effect on either leaf or flower length. The influence of DIF on stem elongation suggested that thermomorphogenesis was not a function of total plant carbohydrate or carbohydrate translocation. Instead, DIF appeared to influence the endogenous gibberellin content or the response of plant tissue to gibberellin. Similarities between thermomorphogenic plant responses and photomorphogenic plant responses suggested that these two processes may be related with respect to their perception and/or transduction.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11283.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

The spatial and temporal variability in the seed bank of a semiarid grassland in Colorado was evaluated using soil cores. Spatial variability in the soil storage of germinable seeds was assessed by sampling two shortgrass plant communities on sites with the same climatic conditions but differing in soil texture. Differences between communities were largely the result of annual plant seeds. Eight sampling dates over two years were used to assess temporal variability, which was more important to the storage of germinable seeds than spatial variability. Differences in the numbers of seeds stored were found between the two sampling years, and seasonally within years. The number of seedlings that emerged from the samples ranged from 122–2,748/m2. A poor correspondence was found between the species composition of the plant communities and the storage of germinable seeds; however, the species composition of the seeds produced on the sites tended to have a high similarity with the seedlings that emerged. Most of the species had a transient rather than a persistent presence in the seed bank.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11284.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Floral morphology and phenology and the timing of stigmatic receptivity and pollen viability were studied to elucidate the mechanisms by which self‐pollination inLupinus nanussubsp.latifoliusis minimized under natural conditions. Pollen germination and pollen tube growth suggest that a physiological self‐incompatibility system does not exist. Instead, self‐pollination is minimized by protandry and by a collar of peristigmatic hairs, which initially inhibit access of autologous pollen to the stigma. These hairs subsequently wilt, permitting self‐pollination of unvisited flowers. Pollen germinates in vivo one day before substantial metabolic enzyme activity can be detected. Citric acid cycle enzymes are not detectable in pollen, but those of anaerobic metabolism are. Beginning on the second day postanthesis, stigmatic secretions exude from weak areas on lateral walls of the elongate epidermal papillae, welling up in the interstices between these cells. This contrasts with the stigmas of other papilionoid legumes, in which secretions accumulate beneath the cuticle covering the stigmatic cells, and the often‐thin cuticle must be ruptured before pollen and exudate can come into contact.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11285.x

出版商:Wiley    

年代:1989

数据来源: WILEY

摘要:

Patterns of growth, and of flower and fruit production, were monitored over two years in a population of the orchidAspasia principissaReichb. f. in central Panama. Observations and experimental manipulations were used to determine the relative importance of pollinator and resource limitation on fruit production. Within a season, fruit production was limited by pollinator availability. Fruit set for hand‐pollinated flowers was over six times greater than that for naturally pollinated flowers. However, in plants that produced more than one fruit, fruit size declined in subsequent fruits, indicating that resources could limit seed production within a season. Plants producing fruits in 1986, on average, produced smaller shoots and inflorescences in 1987 relative to plants that flowered but produced no fruit in 1986. Thus, plants are likely to be resource limited over their lifetimes. Most individuals of reproductive size (82.5%) did not produce fruit over a three‐year period. The reproductive dominance of a few individuals in this population ofAspasia principissamay have important implications for understanding the population structure of the species and the high species diversity of orchids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1989.tb11286.x

出版商:Wiley    

年代:1989

数据来源: WILEY