摘要:

A general account of the stem apex organization in ferns is presented in support of the classical single apical cell concept. The range in variation of apical cells and of their modes of division are described. Evidence is brought out to indicate probable directing effects of the apical cell on modes of division of surrounding cells and on the leaf mother cell. Initiation of and eventual establishment of a stabilized apex in fern leaves is described. Of the more than 50 genera studied, the leaves of all are traceable to a single mother cell from which the leaf apical cell is cut out. Apical dichotomies are described in a number of genera as well as their effect on early leaf development. Results are discussed in a phylogenetic and morphogenetic context of leaf appendicularization.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15712.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Potato tuber discs were examined as a possible quantitative bioassay for studying tumor induction byAgrobacterium tumefaciens. Discs from two potato varieties, Pontiac and Russett Burbank, were inoculated and cultured on water agar plates. Tumors appeared within 10 days. Both the number and weight of tumors per disc increased linearly for inoculum concentration between 1 × 107–1 × 109cells per ml. Polarity, position of the disc relative to tuber epidermis, potato variety and the light conditions did not influence the tumor formation. The simplicity of the procedure and the homogeneity of the tissue, together with the fact that it is a quantitative bioassay, makes the potato tuber disc an ideal system for the investigation of biochemical step(s) associated with the transformation process.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15713.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Fifty‐six randomly selected bear oak trees were moved into growth chambers to determine the influence of relative humidity at the time of flowering on fruit set. The effect of humidity greater than 61 % was to greatly reduce fruit set. Trees which were kept in a chamber where relative humidity was less than 50 % had significantly higher fruit set.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15714.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Pennisetumsect.Pennisetumincludes two reproductively isolated species.Pennisetum purpureumSchumach. is a tetraploid (2n= 28) perennial species which occurs throughout the wet tropics of the world.Pennisetum americanum(L.) Leeke is a diploid (2n= 14) annual species, native to the semi‐arid tropics of Africa and India, and contains three morphologically diverse subspecies. Subspeciesamericanumincludes the wide array of cultivated pearl millets. Subspeciesmonodiifrom the Sahel of West Africa is identified as the wild progenitor of pearl millet. Subspeciesstenostachyumis morphologically intermediate between subsp.americanumandmonodiiand includes the mimetic weeds often associated with the cultivation of pearl millet.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15715.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

The pollen organFeraxothecagen. n. is described from Pennsylvanian age coal balls from the Lewis Creek, Kentucky, locality. The fructifications consist of bilaterally symmetrical synangia composed of a basal pad supporting elongate sporangia that are laterally appressed for the entire length of the sporangial cavities. Sporangial tips extend over the center of the synangium and delimit a small open area, while the bases arise from a parenchymatous cushion that is bounded by short tracheid‐like cells. Each synangium is borne on the surface of an expanded pinna tip and is surrounded by a small amount of laminar tissue that envelopes the base of the synangium. Ultimate pinnae are rectangular in transverse section, possess an elliptical vascular bundle surrounded by canals containing a yellow froth‐like substance, and have a cortex of elongate cells that radiate from the center of the axis. Sporangia contain small (40–64μm), radial, trilete spores ornamented by regularly spaced coni or blunt tipped grana.Feraxothecais compared with the compression genusCrossothecaand some new ideas are advanced concerning the morphology of this compression genus. The obvious differences betweenFeraxothecaand other lyginopterid pollen organs strongly suggests that the Lyginopteridaceae, as it is currently interpreted, is an unnatural family.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15716.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

A new trichome type for the genusLycopersiconis described inL. esculentumMill. It is a short (0.03–0.08 mm), pendant, glandular hair with a club‐shaped head consisting of 8–12 cells. Two previously described “hairless” mutations were examined microscopically. One,hl, does not affect the frequency of hairs nor the number of cells per hair, but causes abnormal enlargement of the stalk cells of all hair types, and thus produces shortened, extremely bent and twisted hairs. Observations on the time of action of this gene indicate that in trichome development two to four cell divisions occur prior to any appreciable cell enlargement. The second mutation,h, affects only the large type of trichome. This mutation effects a developmental shift from trichome to stomatal apparatus at the apex of the multicellular base normally supporting the large trichomes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15717.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Roots ofP. virgatumseedlings have been found to be associated invariably with a symbiotic bacterial species. These bacteria were found both on the surface of, and buried in, the outer walls of the more basal elongating epidermal cells. Often the morphology of the wall‐associated bacteria suggested that they were infected with a virulent phage. Other observations included the sudden appearance of virus‐like particles in the cytoplasm of these basal elongating epidermal cells. Since the appearance of phage‐infected bacteria was found to coincide with the appearance of the cytoplasmic virus‐like particles, and since these two events also coincided with the culmination of the ontogeny of large epidermal cytoplasmic inclusions (ECI) in these cells, it has been suggested that these three events may be related.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15718.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

The morphological and vascular characteristics of the nectaries of the species of the Monotropoideae (Ericaceae) reflect the morphology and declination of the flowers. These, in turn, are related to the pollination systems of the species. The nectaries of members of the Monotropoideae exhibit a range in form from slender, elongate projections, to short, stout ones, or to low ridges between the staminal bases.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15719.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

The morphology and anatomy of the shoot apex in germinatingPinus banksianaseeds is described by using scanning and transmission electron microscopy and microspectrophotometry, with special attention given to events preceding the appearance of the first leaf primordia at about 72 hr post‐imbibition. The 2C nuclei begin DNA synthesis at about 43 hr. RNA increases until 52 hr and is followed by a reduction related to cytokinesis. Protein drops after 36 hr, apparently related to digestion of storage protein bodies, which by 48 hr are about 50% digested. The resulting protein body vacuoles do not enlarge. Starch is digested just prior to appearance of the leaves and may be mediated by α‐amylase production from stacks of endoplasmic reticulum. Heterochromatin increases in the nuclei during germination and coincides with an increase in repeated nucleotide sequences. Golgi bodies increase in number after the first mitoses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15720.x

出版商:Wiley    

年代:1977

数据来源: WILEY

摘要:

Material described by Graham asCyathotrachus bulbaceusis believed to represent a new genus that is a common constituent of Upper Pennsylvanian coal balls. The sessile synangia ofAcaulangiumgen. n. are borne in a row on either side of the pinnule midrib and are composed of four to six short, tapering, laterally appressed sporangia. The sporangia have extended tips which curve over the inside of the synangium distally and delimit a small open area inside the synangium. The outer facing walls of the sporangia are two to three cells thick throughout while the inner facing walls are uniseriate. During dehiscence the sporangia separate laterally and spore release results from the rupture of a row of elongate cells along the inner sporangium midline. Among species ofScolecopteristhe new genus resemblesS. illinoensisandS. minorvar.parvifoliabut differs in its sessile synangial attachment. The additional parenchyma present between sporangial cavities in the synangia ofAcaulangium, and the tendency toward bilateral symmetry suggests an early stage in the evolution of a bivalve synangium such as is present inMarattia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1977.tb15721.x

出版商:Wiley    

年代:1977

数据来源: WILEY