摘要:

Thirty‐five species belonging to various dicotyledonous families were investigated to study the origin, development, and probable function of the shell zone, which is defined as an arcuate zone of cambiform cells delimiting the early axillary bud meristem. It is present in the majority of the investigated plants and five intergrading patterns of origin are described: (i) from the parenchymatized derivatives of the cells of the peripheral meristem of the shoot apex, adaxial to the bud meristem, (ii) from the peripheral meristem of the shoot apex along with the initiation of the early bud meristem, (iii) from the adaxial cells of the bud meristem, (iv) from the derivatives of the cells of the bud meristem at its base, and (v) partly from the parenchymatized cells of the peripheral meristem adaxial to the bud and partly from the adaxial derivatives of the bud meristem. The shell zone loses its identity at different stages of bud development in various species. Its cells ultimately contribute to the ground meristem, procambium, and pith cells of the axis. InCuminum cyminumandlpomoea cairicathe shell zone contributes in bringing about the axillary position of the bud from its early lateral position. InSolarium melongena, derivatives of the shell zone initiate the internodal elongation between the flower or inflorescence and the shoot apex, ultimately shifting the bud to an extra‐axillary position on the internode.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10140.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Benzylaminopurine, indoleacetic acid, and the auxin inhibitors transcinnamic acid, triiodobenzoic acid, and dinitrophenol were employed to elucidate the role of apical dominance and hormones during regeneration of thalli and gemmae ofMarchantia polymorphaL. The cytokinin suppressed normal gemma germination and led to the development of nodular, callus‐like growths. When removed from the influence of benzylaminopurine, the site and magnitude of normal thallus outgrowths varied with the length of time that the tissue had remained on the cytokinin‐containing medium. This aberrant germination was not influenced by the incorporation of indoleacetic acid into the medium. Exogenous auxin neither accelerated nor inhibited the regeneration of normal thallus growth on excised vegetative discs. Transcinnamic acid and dinitrophenol inhibited regeneration. Auxin reversed this suppression. Triiodobenzoic acid did not significantly affect regeneration. Autoradiographs demonstrated a pronounced accumulation of labelled auxin in the midribs and the acropetal regions of excised thallus discs. This evidence suggests that there is an endogenous, basipetal auxin gradient inMarchantia;that the maintenance of this gradient is vital to normal growth and regeneration of the thallus; and that high endogenous concentrations of cytokinin destroy this polarity by increasing the auxin‐synthesizing capacity of the tissue.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10141.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Ethylene (50 ppm) and 2,4‐D (1 mm) inhibit xylogenesis and completely prevent fiber lignification in the third internode of etiolated pea seedlings(Pisum sativumvar. Alaska) during 96–240 hr of treatment. When ethylene is removed after 72 hr, normal differentiation resumes; thus the gas causes no irreversible damage to the cells. A combined treatment with 50 ppm ethylene and 50 μm2,4‐D or treatment with 1 mm2,4‐D alone causes inhibition similar to that observed with 50 ppm ethylene, and 50 μm2,4‐D is partially effective. The inhibition of xylogenesis and fiber lignification caused by 2,4‐D is partly or wholly due to auxin‐induced ethylene production.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10142.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Ultraviolet reflectance properties of flowers in 26 East Mediterranean wild species and three cultivated species of the Cruciferae are surveyed. These properties were disclosed by photography of fresh or herbarium specimens through a visible‐light absorbin filter. The so‐revealed spectral polymorphism is related to the previously known visible flower colors. Ultraviolet floral patterns which act as nectar guides to pollinators are described. Hitherto unreported patterns were found to result from ultraviolet absorption by sepals, ultraviolet reflection from anther tips, and, in one case, ultraviolet absorption by a peripheral part of the corolla. In some cases patterns differ between closely related taxa and could therefore be of diagnostic value.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10143.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Quantitative changes in DNA, histone, RNA, and total protein have been measured in meristematic cells during floral evocation.2A single 22‐hr, long‐day exposure induced two‐month‐old vegetative plants ofSinapis albato flower. Periodic collections of shoot apices were made and stained with Schiff's reagent (DNA), azur B (RNA), alkaline fast green (histone), and naphthol yellow S (total protein). The two‐wavelength method was used for DNA and histone measurements and the one‐wavelength, two‐area procedure was chosen for RNA and total protein determinations. The DNA and histone amounts per cell decreased to a minimum value 34 hr after treatment, and most of the nuclei shifted from 4C to 2C values. DNA and histone quantities paralleled each other from 34–46 hr, after which time the histone values continued to increase and the DNA values decreased. The RNA values increased rapidly after treatment as did the total protein quantities, after a slight decrease at 34 hr concurrent with the 4C to 2C cell population shift. The significance of these events is discussed in relation to the changes which were previously described in the shoot apex ofSinapisin transition to flowering.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10144.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

The structure of the Royal Ann cherry cuticle (Prunus aviumL.) was determined and interpreted in the light of its possible significance to cuticular penetration by a SO2‐calcium bisulfite brine. The morphology of the cuticle was determined by standard histological and histochemical techniques. The surface structure of the cuticle was found to have a smooth to granular sheet or layer of surface wax, which when removed revealed a porous sponge‐like surface. The cuticular surface showed intermittent birefringence, which increased as the fruit matured. Ectodesmata were found to occur over anticlinal walls and in guard cells on both sides of the fruit, with more on the side opposite the suture. Both sides had stomata with more occurring on the suture side. Secondary bleaching was found to alter the structure and permeability of the cuticle.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10145.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Details of organogenesis, anatomy, and some aspects of histogenesis are described for the inflorescence units and flowers of the mangrove palm,Nypa fruticans. The genus is of special interest in evolutionary studies because of its disjunct morphology and substantial fossil record. The inflorescence is an erect monopodial axis bearing 7–9 lateral branches and ending in a pistillate head. The lowest of the lateral branches bears up to six orders of branches, the next ones progressively fewer, and the uppermost is usually unbranched. Lateral branches of all orders end in thick spicate, staminate rachillae. The rachillae and the pistillate head consist of spirally inserted sessile flowers, each borne in the axil of a bract. Staminate and pistillate flowers are similar in structure. Both have three separate sepals and three separate petals, which are loosely closed in bud. Staminate flowers have no pistillodes; nor are there any staminodes in the pistillate flower. The androecium consists of a stalk bearing three anthers distally and is shown to represent three stamens with filaments congenitally fused and anthers connate by the ventral faces of the connectives. The pistillate flower has three separate carpels, which expand rapidly so that by anthesis they much exceed the perianth. Each carpel is cupulate in shape, with a two‐crested distal opening, and receives ca. 150 vascular bundles, many of which may branch dichotomously. No dorsal or ventral bundles can be definitely distinguished, but a ventrally open ring of 10–12 bundles surrounding the locule matures first. Allometric growth clearly accounts for much of the morphological disjunction in the reproductive organs ofNypacontrasted with those of other palms. Resemblances to coryphoid, ceroxyloid, arecoid, and cocosoid palms are indicated by these studies. Different combinations of characters and several distinctive features justify a separate major taxonomic category for this genus within the Palmae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10146.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Excised cultured roots ofRaphanus sativusL. cv. White Icicle elongate and produce a few lateral roots but do not increase in diameter. Lateral expansion is effected when both an auxin (indoleacetic acid or naphthaleneacetic acid) and a cytokinin (benzyladenine) are applied at the cut end of the root. The growth regulator effects are apparent first in the pericycle and subsequently in the procambium. Both of these groups of cells divide, producing large numbers of secondary derivatives. The increase in number of cells is reflected in an increase in root diameter. When cultured roots are treated with auxin only, a limited number of pericycle cells divide and lateral roots develop. When roots are treated with cytokinin only, all pericycle cells divide and a multiseriate zone of pericycle‐derived cells develops. The procambium is not markedly affected by application of a single growth regulator. The distinct and separable responses of pericycle cells to different regulators suggest that the pericycle can be characterized in a functional, as well as a topographic, sense.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10147.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Aqueous extracts of fresh roots and shoots ofAndropogon virginicus(broomsedge) were found to be inhibitory to the growth of seedlings ofAmaranthus palmeri, Bromus japonicus, Aristida oligantha, andAndropogon scoparius. The first two species are often important in the pioneer stage of old‐field succession in eastern Oklahoma,Aristidais prominent in the second stage, andAndropogon scopariusis important later in succession including the climaxQuercus stellata–Quercus marilandicasavanna. Sterile dilute extracts of roots and shoots of broomsedge were inhibitory to two test species ofAzotobacter, a free living nitrogen fixer, and to two species ofRhizobium, a symbiotic nitrogen fixer. Small amounts of decaying shoots of broomsedge (1 g per 454 g of soil) were very inhibitory to the growth of the four test species listed above and toAmaranthus retroflexus, another species often important in the first stage of succession. Similar amounts of decaying material in soil also significantly inhibited growth and nodulation of the two most important species of legumes in old‐field succession in eastern Oklahoma,Lespedeza stipulaceaandTrifolium repens. Broomsedge is known to compete vigorously and grow well on soils of low fertility, so the inhibition of nodulation of legumes could help keep the nitrogen supply low and give broomsedge a selective advantage in competition over species that have higher nitrogen requirements. The combined interference of broomsedge against other species resulting from competition and allelopathy could help explain why it invades old fields in 3–5 yr after abandonment from cultivation and remains so long in almost pure stands.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10148.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

The majority of the seeds of the winter annualDraba vernaL. require light for germination, but light can be given before they are fully after‐ripened and as long as 4 months before temperature and moisture conditions are favorable for germination. Seeds that are exposed to light in late spring, or in late spring and early summer, and then removed to darkness can germinate under favorable temperature and moisture conditions in autumn, even after passing through a long unfavorable (for germination) wetting and drying period at high summer temperatures in darkness. The light requirement for germination probably is not an important factor restrictingD. vernato open, well‐lighted habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10149.x

出版商:Wiley    

年代:1972

数据来源: WILEY