摘要:

The nuclear genepmofOenothera hookeriT.&G. strain Johansen increases the frequency of plastome mutations. These plastome mutations are visible because they form variegation sectors. A distinctive feature of thepmsystem is the large number of different phenotypes induced by the plastome mutator. The fine structure of four plastome mutants has been studied using electron microscopy. Each of the four mutants had a unique phenotype which was characterized by the amount of thylakoid development, the number of plastoglobuli, and the dilation of thylakoids with age. The developmental sequence of the phenotype of one of the mutants was studied by following plastid development in progressively larger leaves. The phenotypes of thepm‐induced mutants are generally similar to those of spontaneous plastome mutations described in the literature.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08592.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Shoot apices of a short‐day sensitive line ofNicotiana tabacumL. cv. NCTG‐22 have been examined by electron microscopy for ultrastructural changes which occurred in the central zone over a 17‐day period during the transition from vegetative to reproductive growth. Plants were grown in controlled‐environment chambers of the NCSU Phytotron and exposed to an inductive photoperiod after a 6‐wk juvenile phase. Ultrastructural changes were investigated from photomicrographs using a semi‐automatic stereological procedure and a microcomputer. After exposure to only one inductive cycle cell and nuclear cross sectional areas in short‐day plants were significantly larger than in long‐day controls. Subsequently, under short days cross sectional areas of cells, nuclei, vacuoles and proplastids decreased, while mitochondrial cross sectional area and relative volume increased during the course of the induction period. In induced apices as cross sectional areas and relative volumes of vacuoles and proplastids decreased, their profile numbers increased. The reduction in cross sectional areas of cells and most organelles was associated with an increase in rate of leaf initiation and size of the apical dome. The demand for sufficient energy input to maintain the surge in growth and activity preceding floral initiation was reflected by the significant increases in cross sectional area, profile numbers and density of the mitochondria population. Even though the transition period is quite long forNicotiana, cells and organelles in the central zone were observed to progress through similar changes in morphology that are known to occur inSinapisandXanthiumwhich exhibit a more rapid and absolute response to photo‐induction.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08593.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

The genusPenthorumL. consists of two species of perennial herbs,P. sedoidesof eastern North America andP. chinenseof eastern Asia.Penthorumhas long been considered intermediate between Crassulaceae and Saxifragaceae. An anatomical study of both species was undertaken to contribute to a better understanding of the relationships of these plants. Prominent anatomical features ofPenthoruminclude: an aerenchymatous cortex and closely‐spaced collateral vascular bundles of stems; one‐trace unilacunar nodes; brochidodromous venation, rosoid teeth bearing hydathodes, and anomocytic stomata of leaves; angular vessel elements with many‐barred scalariform perforation plates and alternate to scattered intervascular pits; thin‐walled non‐septate fiber‐tracheids; abundant homocellular erect uniseriate and biseriate rays; and absence of axial xylem parenchyma. In general,Penthorumpossesses neither the morphological nor the anatomical synapomorphies which define Crassulaceae, and features shared with Saxifragaceae are largely symplesiomorphous. ThusPenthorumis probably best classified in the monogeneric Penthoraceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08594.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Pollinator response to petal color polymorphism in wild radish(Raphanus sativus)was investigated. Behavior of insect visitors was observed within experimental flower arrays, each containing two of the petal color forms seen intermixed in California populations: white, yellow, pink, and bronze. Honeybees, which accounted for almost 90% of all visits, typically preferred yellow or white flowers and discriminated against bronze. Their preference for white increased significantly as theRaphanusflowering season progressed. Syrphid flies were also frequent visitors and increased in abundance near the end of the season. Syrphids typically preferred pink to other colors. Individual honeybees tended to specialize on either yellow or pink flowers on a short‐term basis. This foraging pattern provides the potential for positive assortative mating among plants with yellow or pink flowers. Intraspecific pollinator discrimination may influence genotypic frequencies as well as the relative maternal and paternal reproductive success of color morphs.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08595.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Wild radish(Raphanus sativus)populations in California contain several conspicuously different petal color morphs. Pollinators are known to discriminate among color variants, and this study was done to determine whether such discrimination influences seed and fruit production. Seed set potential, as determined by total flower production and the number of ovules per flower, did not vary among color morphs. Total fruit set was high in these populations, ranging from 60% to 80%, and did not vary significantly among common petal colors in any site. The number of seeds per fruit did vary among color morphs, but the pattern was different in 1983 and 1984 and did not correspond to concurrent patterns of pollinator visitation. Hand pollination studies showed that pollen limitation is not a major factor influencing seed production; in 1984, addition of pollen to flowers failed to enhance fruit or seed set, while in 1983, addition of pollen slightly increased the number of seeds per fruit. Additional experiments demonstrated that all petal color morphs were mostly self‐incompatible. Resource limitation appeared to be a major force regulating seed production. Despite consistently high pollinator visitation rates, flower production rate, fruit set, and seeds per fruit all declined markedly through the five wk flowering season. Pollinator discrimination among colors is likely to have its greatest impact on paternity success rather than maternal fecundity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08596.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

We present here the first study of the embryology ofHeteropyxis, in order to evaluate its relationships with Myrtaceae, a family in which it has often been placed. On the basis of embryology,Heteropyxisis undoubtedly very closely allied to Myrtaceae, but is distinct in possessing 1) a bisporic Allium type embryo sac, 2) a condition in which the two microsporangia of the theca are remotely separate from each other and dehisce by their respective longitudinal slits instead of by a common slit, and 3) an ovule and seed that has wings on both ends. All of these embryological characteristics are apomorphic features; they contrast with many other characteristics of the genus, such as its completely superior ovary and separate staminal traces, which are clearly primitive ones. Like the unique monotypicPsiloxylon, an endemic of Mauritius,Heteropyxisclearly diverged early from the evolutionary line leading to Myrtaceae before the origin of the common ancestor of that family (excludingHeteropyxisandPsiloxylon). Heteropyxiscould logically be regarded either as a subfamily of Myrtaceae distinct from all other members of the family or as a separate but related family. We shall return to this question when our review of the embryological features ofPsiloxylonhas been completed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08597.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Microsporogenesis was investigated in hermaphroditic and male‐sterile plants in nine gynodioecious taxa of HawaiianBidens.Normal microsporogenesis in hermaphrodites and the onset of abortion in male steriles were similar in all taxa and in a hybrid between two gynodioecious species. The early abnormal vacuolation of tapetal cells is the first visible evidence leading to premeiotic abortion of microsporogenesis in male steriles. The sporogenous cells disintegrate rapidly after the vacuolation of the tapetum, resulting in a shrunken, indehiscent anther which is composed of only the epidermal layer with some remnant cells of the endothecium and the connective at anthesis. In hermaphrodites, the tapetal cells remain dense and undergo karyokinesis to become binucleate during meiosis I. The tapetum becomes plasmodial after microspores are released from tetrads and gradually disappears during pollen formation. The genetic factor(s) which cause the abortion act with remarkable precision and consistency in all taxa investigated. This suggests that gynodioecy in all HawaiianBidensis homologous and the establishment of male sterility in HawaiianBidensoccurred only once. The spread of the genetic male‐sterile factor(s) may be the result of adaptive radiation of the original gynodioecious species or natural interspecific hybridization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08598.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

We launched imbibed seeds and seedlings ofZea maysinto outer space aboard the space shuttleColumbiato determine the influence of microgravity on 1) root‐cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth‐grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth‐grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and elipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar ofZ. mays.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08599.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Flavonoid aglycone variation withinHelianthus annuus, a species widely distributed throughout North America, was analyzed. Flavonoid aglycones ofH. annuusconsist of two types, flavones and chalcones. The flavone aglycones are sequestered in glandular trichomes that occur on both leaf surfaces, whereas the chalcone aglycones appear to be incorporated in the waxy leaf cuticle. Considerable variation in flavonoid profile was observed with some plants exhibiting as few as one, and others as many as seven of the eight aglycones detected. No definable phytogeographic patterns were observed for this flavonoid variation. Flavonoid aglycone variation also did not differentiate the infraspecific taxa withinH. annuus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08600.x

出版商:Wiley    

年代:1987

数据来源: WILEY

摘要:

Algae‐ and bacteria‐free seedling cultures of the seagrassThalassia testudinwnBanks ex König were utilized to evaluate effects of nutrient enrichment on growth and chemical composition. Seedlings cultured in media based on both synthetic seawater andNH‐15 medium amended with inorganic nitrogen (NH4+) and organic nitrogen (glutamine, glutamate, urea and yeast extract) exhibited no growth enhancement relative to controls in the growth parameters measured. General decreases in green leaf areas and leaf widths after one month coupled with relatively high C:N ratios after 3 months in culture suggest utilization and depletion of stored reserves with little or no assimilation of exogenous nutrients. These observations coupled with previous results in non‐axenic seedling cultures indicate microbial associations may play a critical role in the nutrient physiology of this species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1987.tb08601.x

出版商:Wiley    

年代:1987

数据来源: WILEY