摘要:

The peculiar secondary growth inDoxantha unguis‐catiprovides several developmental problems concerning cambial activity. One of the most interesting of these problems is the presence of both unidirectional and bidirectional arcs of cambium within the same stem. This investigation reports the ontogenetic development of these two kinds of cambial arcs. The first cambial divisions are observed in the fascicular regions of the 11th to 16th internodes from the shoot tip. This event is initiated after internode elongation is completed. In the initial stages, secondary tissues have a cylindrical configuration, but subsequently four grooves become apparent. These grooves signify the first evidence of unidirectional cambial activity. The four unidirectional arcs occur near the four major vascular strands to which all of the leaf traces connect. As secondary growth continues, the bidirectional and unidirectional arcs of cambium become separated and radial fissues can be seen between the furrows of phloem and the lobes of secondary xylem. Additional furrows originate either as sets of four between the original set of four or as single furrows to either or both sides of an existing furrow. All furrows are bordered by multiseriate rays. The initials of the bidirectional and unidirectional cambial arcs are non‐stratified and are similar in size and appearance. The phloem produced within the furrow differs in several respects from that produced by the bidirectional arcs. The two types of cambial activity and the precise locations of the unidirectional cambial arcs in the stem (i.e. near the four major strands) suggests that transported products from the leaves are involved in the control of unidirectional cambial activity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10022.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The ontogeny of the upper Pennsylvanian age gymnospermous ovule,Callospermarion pusillum, is described from petrifaction specimens collected at the Berryville locality in Illinois. Ovules exhibit a wide range of dimensional and structural features that indicate an extensive developmental sequence. Specimens range from ovules with indistinct zonation of the thin‐walled integument to those with thick‐walled cells of the sclerotesta. The apex of the fleshy nucellus in some specimens is preserved as a cellular mound, while in others a well‐formed cellular pollen chamber is present; still other ovules are characterized by a papery‐thin nucellus and pollen chamber wall. The megagametophyte of most specimens is represented by a hollow megaspore membrane that may be restricted to the base of the nucellus, or occupy the entire seed cavity. In a few specimens cellular gametophytes are preserved, and in one ovule archegonia with supposed eggs are also present. Variability in each of the features is compared with ontogenetic changes in comparable structures of living gymnospermous ovules and is correlated with ovule size. A developmental sequence for the fossil ovules is proposed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10023.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Isoenzyme patterns of acetone‐extracted proteins revealed a close similarity betweenChlamydomonas eugametosandC. moewusiibut a distant relationship between the two andC. reinhardtii. Chlamydomonas eugametosandC. moewusiihad identical banding patterns of malate dehydrogenase (MDH) and leucine aminopeptidase (LAP) in starch gels. These two species exhibited the same MDH distribution spectrum in analytical disc polyacrylamide gels but neither species showed definitive LAP or glutamate dehydrogenase (GDH) activity. There were differences in the starch gel alpha esterase (α‐EST) patterns ofC. eugametosandC. moewusiidue to an additional weak band at Rf 0.75 in the latter species and a slight variation in the position of another band at Rf 0.80–0.82. Some variations between the two species also occurred in the α‐EST banding in disc gels at Rf 0.70–0.85 and at Rf 0.06–0.14 withC. moewusiiexhibiting the greatest number of bands.Chlamydomonas reinhardtiidisplayed patterns of all four enzymes but the band characteristics were distinctively different from those ofC. eugametosandC. moewusii. There appeared to be no obvious isoenzyme difference between mating types of either species. It is concluded thatC. eugametosandC. moewusiiare not identical species but are closely related in regard to the enzymes assayed. Isoenzyme analysis is considered to be a useful approach to algal systematics.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10024.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Petunia (Petunia hybridaVilm. cv. ‘Snowstorm') plants were grown in saline solution (NaCl, MgCl2, and/or CaCl2) of 0, 1, 2, and 3 bars osmotic pressures. Pollen viability was tested by tetrazolium chloride staining and by germination (by the hanging drop method, using 15 % sucrose and 0.01 % boric acid as the nutrient medium, at 27 ± 1 C). Pollen viability decreased with increased salinity. Pollen from plants grown in single salt solutions of NaCl, MgCl2, and CaCl2(each at 0, 1, 2, or 3 bars osmotic pressure) was germinated in base culture medium. Pollen viability decreased more with NaCl than with MgCl2or CaCl2. In vitro studies of the effects of three salts, viz., NaCl, MgCl2, and CaCl2, on pollen germination and tube growth showed that NaCl inhibited germination and pollen tube growth more than did MgCl2or CaCl2. MgCl2was least injurious, and even promoted tube growth at 0.5 and 0.75 bars osmotic pressure. Adding low concentrations of MgCl2reduced the toxic effect of NaCl and increased the percentage of germination. CaCl2reduced the effect of NaCl less than did MgCl2. We conclude that specific ion effects were more important than osmotic pressure.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10025.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Spores of the heterotrichous mossPylaisiella selwyniiKindb. were sown in a defined inorganic liquid culture medium and incubated at 27 C with a 16‐hr photoperiod. They germinated at 7–10 days, and formed a few caulonemal buds at 27–30 days which developed into gametophores by 40 days. Bud formation and gametophore development followed a pattern common to many mosses. Addition of a virulent strain ofAgrobacterium tumefaciens(B6) to the moss cultures increased bud formation and hastened the time of their appearance by 5–6 days. With 109or more bacteria per ml of moss culture medium the percentage of plants with gametophores at day 35 after the spores were sown was 96 % or greater, as opposed to 0–24 % in the controls. The mean number of gametophores per responding plant was also increased from one per plant in controls to 4–6 per plant in inoculated cultures. Addition of the bacterium at day 17–18 of culture was as effective as early additions of the bacterium, suggesting that the moss must become ready to bud before the bacterium can influence its development. The promotion of gametophore formation was directly related to the number of bacteria added and depended upon the presence of viable bacteria. The supernatant from bacterial cultures did not promote gametophore formation. The changes induced byA. tumefacienswere similar to those reported for cytokinins.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10026.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The haplord chromosome numbers ofn= 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species ofMelampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series ofx2 = 9, 10, 11, and 12. Of these four groups of species, thex= 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base inMelampodium. A comparison of morphological and cytological data from the closely related genera,AcanthospermumandLecocarpus, indicates that the latter are probably on a common base ofx= 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10027.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

New specimens ofTriloboxylon ashlandicumMatten and Banks (1966) show additional features of the anatomy and morphology of the plant. The primary xylem has strands of parenchyma associated with trace formation. Secondary xylem and phloem are described for the first time. The outer cortex, previously unknown, contains hypodermal fiber strands. The ultimate appendages are much divided and planated. Specimens ofAneurophyton hallii(Arnold, 1940) were reexamined and newly prepared. They are transferred to the genusTriloboxylonasT. hallii. Triloboxylonis transferred from Pteropsida‐Incertae Sedis to the Aneurophytales. New information on the morphology and anatomy ofTelraxylopterisis presented and its identity toSphenoxylonis supported.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10028.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Frequency data for 21 species of corticolous macrolichens in 14 upland forest stands were analyzed in relation to a number of environmental variables, using correlation and ordination techniques. Results indicate the predominance of macroclimate—especially precipitation—in determining the frequency behavior of bark lichens within the limited area of this study. Less important, though significant, factors include the frequency of preferred host‐tree species, the age structure, and tree‐species composition of stands.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10029.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

A large collection of specimens, consisting primarily ofArchaeopteris macilenta, forms the basis for an anatomical and morphological study of the lateral branch systems. Emphasis is placed on the main axes of the branch systems, which are found to be characterized by a variable number of orthostichies of lateral appendages, ranging from 7 to probably 11. The number of orthostichies seems to correspond to the number of ribs of the stele. There may be an equal number of rows of leaves on either side of the plane in which the two rows of lateral branches lie, or one side may have one or two more leaf orthostichies than the other. In all specimens for which both part and counterpart were available, however, there is a greater density of leaves on one side (hypothesized to be the adaxial) than on the other, caused primarily by an apparent abortion of leaf primordia early in development on the side of least density. Leaves and branches occur in the same ontogenetic spiral and in one specimen comprise a ‘phyllotaxis’ of 2/9 and contact parastichies of 5 + 9. On both the main and lateral axes, leaves are characterized by long, decurren bases which essentially ensheath the axrs on which thay are borne. Phyllotaxis and the correlated stelar form apparently vary considerably withinArchaeopteris. It is suggested thatArchaeopteriswas more closely related to the coniferophytes than to any other gymnosperms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10030.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The simple, efficient method described here for the study of ovule and megagametophyte development in angiosperms provides for the extension of investigation beyond the limits imposed by the traditional but arduous section technique. Excised pistils previously fixed in FPA50and stored in 70 % ethanol are placed in a clearing fluid composed of lactic acid (85 %), chloral hydrate, phenol, clove oil, and xylene (2:2:2:2:1, by weight). After 24 hr, ovules dissected from the ovularies are transferred with some of the fluid to a slide, covered so that the cover glass is supported laterally by two permanently affixed covers, and examined with phase contrast optics. The unique action of the clearing fluid permits the study of cellular structure with the phase oil objective focused at any focal plane within the ovule. Downward focusing thus reveals a series of optical sections in the sagittal, frontal, or transverse plane depending on the orientation of the ovule. Orientation can be altered by a slight shifting of the cover glass on the lateral support mounts. The ovules become quite fragile in the clearing fluid. Pressure applied to the cover glass gradually breaks the ovule apart without disrupting the structural integrity of individual cells. This squash procedure provides for extending observations to cytological features of megasporocytes, megaspores, and megagametophytes previously identified in intact ovules. The new method is applied here to the study of ovule development in two unrelated species,Cassia abbreviataOliver var.graniticaBak. f. (Leguminosae) andLudwigia uruguayensis(Camb.) Hara. (Onagraceae). For best results, the ovules ofLudwigiamust be pretreated in lactic acid (85 %) for 24 hr prior to application of the clearing fluid. Other methods for pretreatment likely will be required as the technique is applied to a wider range of flowering plant species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb10031.x

出版商:Wiley    

年代:1971

数据来源: WILEY