摘要:

Surface area of wood and bark is an important dimension of forests, with implications for respiration rate, energy exchange, and water and mineral budgets. Surface area of stem wood and bark can be estimated effectively from linear regressions on conic surface (one‐half basal circumference times tree height) or from regressions of the logarithm of area on the logarithm of diameter at breast height. Branch surface can be estimated from a formula using branch basal diameter, length, and number of current twigs, and from logarithmic regressions of branch bark surface on basal diameter of branches and breast‐height diameter of trees. In temperate deciduous forests several square meters of plant surface occur above each square meter of ground surface; these plant surfaces include 0.3–0.6 m2of stem bark, 1.2–2.2 m2of branch bark, and 3.0–6.0 m2of leaf blades. Branch bark surface increases more rapidly than leaf surface with increasing size of branches and trees. Growth and aging of trees, and maturation of forests, imply increasing ratios of bark (and wood) surface to the photosynthetic leaf surface which supports its growth and respiration.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10717.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

One of the criteria sometimes used in distinguishing species in the genusPandanushas been the number of carpels which make up each phalange of the fruit. An investigation of the dependability of this criterion yielded results which do not invalidate its use, but its applicability is restricted. In addition a more precise method of obtaining the information required for the use of the criterion is described, involving counts of carpels‐per‐phalange and phalanges‐per‐cephalium based on whole‐cephalium samples. Graphs illustrate some of the variation with respect to carpel number in certain species of the genus. A specific example of the application of the criterion is provided, as are several other examples without detailed data. Cautious use of and limited dependence on the criterion are suggested, and some cases of variation in carpel number within one species are cited. Like all other taxonomic criteria, it should be used in conjunction with all other data and its applicability evaluated for each particular taxonomic case rather than depended upon for quick solutions to taxonomic problems.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10718.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

The most obvious external effect of trifluralin on the primary root was an increase in the amount of radial expansion near the root tip. The initial radial expansion of the treated roots occurred in the region of maximum elongation. With increased duration of treatment there was a gradual decrease in the extent of the meristematic tissue zone because of progressive vacuolation and subsequent differentiation. Although trifluralin disrupted the mitotic process, no one type of mitotic figure prevailed. Mitotic activity was not affected in all of the cells, some of which appeared to be undergoing a perfectly normal mitosis. Rates of trifluralin application sufficient to inhibit lateral root emergence without interfering with development of the primary root affected the pericycle and portions of the endodermis. The pericyclic cells were much enlarged in. the regions opposite the protoxylem and had undergone some of the initial phases of lateral root formation. These enlarged pericyclic cells correspond to what have been called primordiomorphs.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10719.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

The Tropical West African‐Congolese spinyCleomepreviously referred to the neotropical“C. spinosa”is the indigenous, distinct, here newly describedC. afrospina, most closely related to the southern South AmericanC. trachycarpaof the otherwise endemic neotropical SectionTarenaya.Early collections (from 1816) and widespread distribution in wet forests and riversides also indicate it to be indigenous and not adventive. Related also is the widespread Brazilian‐ArgentinianC. hasslerianaChod. (“C. spinosa”auct. non Jacq.;“C. pungens”auct. non Willd.?), the commonly cultivated “Spider Flower,” once recently collected in the Congo (cultivated?). As the only indigenous spiny Old WorldCleome, C. afrospinais a remarkable neotropical element in the African flora. Historical explanations for such disjunctions (continental drift, land bridges) are rejected. Avian long‐distance dispersal is indicated by semi‐aquatic successional habitats of high ecological receptivity, generally annual habit, other highly disjunct vicariads, and self‐compatibility within the group. Similar disjunctions occur in the distribution patterns of many aquatic birds (e.g., whistling ducks—Dendrocygna) and of various tropical plants of ecologically receptive “open” habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10720.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Polysomatism inNicotiana tabacumL. ‘Wisconsin 38‘ was confirmed. Pith samples from the region of the stem 3.5–10.5 cm below the apex contained nearly equal proportions of diploid and tetraploid cells and samples obtained further down, 15.5–22.5 cm, showed predominantly tetraploid (circa 70%) and smaller proportions of diploid (9%), octaploid (16%), and aneuploid (5%) cells. Cultures of the callus from pith explants showed no evidence of diploid cells after 1 year, but did show roughly half 4nand 8neuploid and half‐aneuploid cells. The callus after 6 years in vitro consisted entirely of aneuploid cells. The attainment of this predominance of aneuploid cells could account for the decline of callus growth and organ formation of tobacco tissue cultures. Tobacco tissue cultures started from single cells disclosed that totipotentiality was not restricted to diploid cells but was possessed by and expressed with apparently equal ease by tetraploid cells. The morphogenetically depressed situation was associated with a highly variable aneuploidy. With increase in somatic age the frequency of aneuploid cells increased and the level of ploidy among the aneuploid cells shifted from sub‐tetraploidy to above tetraploidy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10721.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Anther removal from stamens whose filaments are 1–3 mm long restricts filament elongation to approximately 60% of the normal length. Removal of one‐third to one‐half of the anthers affects only the antherless filaments and does not appear to inhibit the growth of the other organs of the flower. Filament growth inhibition induced by anther removal involves both an inhibition of epidermal cell elongation along the length of the filament and also an inhibition of cell division. There is no evidence that the inhibition of filament growth is a response to damage caused by anther removal. Rather, it is suggested that anther removal severs a normal hormonal relationship existing between the anther and the developing filament. The application of gibberellic acid (GA3) in lanolin paste stimulated the elongation of the antherless filaments to achieve an average of 87% of the filament length of adjacent intact stamens. The closer a filament is to having attained its final number of cells before anther removal, the closer does its length come to reaching the final length of filaments in intact stamens. The elongation of these antherless filaments with the application of GA3was accompanied by elongation of the epidermal cells of the filament to normal, or in some cases greater than normal, lengths. There is no evidence that GA3application affected the inhibition of epidermal cell devision induced by anther removal. The results of this study support the suggestion of Plack that emasculation‐induced inhibition in the growth of floral organs and its reversal by GA3is a general phenomenon.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10722.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Previously described procedures which permitted the alteration of the culture medium during the course of development were used to investigate the effects of hydroxy‐l‐proline (hypro) on the gametophytic ontogeny ofScapania nemorosa(L.) Dum. Depending upon the time this compound was supplied during ontogeny, hypro at an initial concentration of 5 × 10–5mdelayed leafy shoot development from protonemata and killed or damaged shoots which had already developed. More significantly, hypro was found to influence morphogenesis profoundly in plants that developed subsequent to treatment. Resulting phenovariations included: modifications in branching pattern, in the size, shape, mode of insertion, and degree of overlapping of lateral leaves; and the unprecedented formation of ventral leaves (underleaves, amphigastria). The finding that low concentrations of exogenous hypro can evoke such modifications is considered to be significant to liverwort taxonomy. The range of phenovariation which occurred in response to hypro, especially the formation of amphigastria, suggests that this compound may be influencing an area, or areas, of metabolism of cardinal importance to speciation and phylogeny in succubous leafy liverworts.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10723.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Petrified seeds of Upper Mississippian age (Chester Series) are described from sediments from northwestern Arkansas. Specimens ofRhynchosperma quinniigen. et sp. n. are radially symmetrical and range in length from 1.2 to 2.2 cm and 1.0 to 1.3 cm at the greatest diameter. The seeds are ovate with a tapered apex having 8–10 integumentary ribs and a broadly rounded chalaza. The integument is two‐parted, consisting of an outer presumably soft tissue with secretory canals and an inner layer constructed of longitudinally oriented thick‐walled cells. Nucellus and integument are confluent, but they diverge near the seed midlevel with the free portion of the nucellus forming a dome‐shaped pollen‐receiving structure. Additional features such as vasculature and the structure of well‐preserved megagametophytes are described. The petrified specimens are compared with taxa instituted for casts and impressions which includeRhynchogoniumandBoroviczia.The ovulate versus cupulate nature of these genera which has remained uncertain until now appears to be settled in favor of an ovular identity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10724.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Circles inOenotheraare normally composed of even numbers of chromosomes. Two cases of trisomic hybrids with closed circles containing an odd number of chromosomes are here reported. The first of these appeared to containβ Trois Pistoles IandhMateoand had a closed circle of 5, an open chain of 8, and a pair; or chains of 9 and 4 plus a pair. The second hybrid seemed to containα Trois Pistoles IIandβ Palmer Lakeand had a closed circle of 5 and an open chain of 10. It was possible to analyze in considerable detail the situation in the first of these. The chromosome 5·12 or 11·6 of orTrois Pistoles Iwas present in this trisomic, which arose either through the simple addition of 5·12 or 11·6 to theβ Trois Pistoles Icomplement contributed through the egg, or through double non‐disjunction. If it were a trisomic of the former type it contained only one chromosome ofα Trois Pistoles I.If it arose through double non‐disjunction, the minimum it could have had would be the equivalent of twoα Trois Pistoles Ichromosomes, and it might theoretically have had up to the equivalent of 5 chromosomes. It showed, however, no influence ofα Trois Pistoles Iin its phenotype, although the twoTrois Pistoles Icomplexes produce very different phenotypes. It is probable, therefore, that the trisomic arose as a result of simple addition of 5·14 or 11·6 ofα Trois Pistoles Ito theβ Trois Pistoles Icomplex received from the mother.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10725.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

The single specimen from the Falling Run Member of the Sanderson Formation is interpreted as a segment of a petiole from a region just proximal to a major branching of the frond. The specimen is characterized, basally, by a four‐lobed primary xylem strand. Following stelar branching there are two outer papilionoid strands that produce alternate traces bilaterally and two inner clepsydroid strands, oriented at right angles to the plane of the frond. The frond, which appears to be a morphologically flattened and modified lateral branch system, is probably of calamopityean or pteridosperm affinity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10726.x

出版商:Wiley    

年代:1967

数据来源: WILEY