摘要:

Diurnal variations in the leaf oils of Valencia oranges [Citrus sinensis(L.) Osbeck] were studied over a period of 4 years. Depending on the season of harvest, a twofold diurnal change in amount of oil can be observed. A quiescent period between flushes was observed in June. The amount of the main individual components varies with the total oil so that the composition of oil shows only small variations. One suggested function for the oil could be as a precursor for higher isoprenoid biosynthesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06203.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Early gametophyte ontogeny was quantitatively distinct for Olympic Peninsula, Alaskan, and disjunct Idaho populations of the homosporous fernBlechnum spicant(L.) J. Sm. Although variable, gametophyte sex expression was shown to have a genetic component. Statistically different patterns of sex expression characterize each population. The Olympic Peninsula populations were distinct from each other but consistent in having a predominantly unisexual pattern. The disjunct Idaho population was predominantly bisexual at the time when comparable field collected gametophytes bear sporophytes. Preliminary experiments suggest that an antheridogen operates in this species. Increased sowing density favors maleness, and an extract from soil cultures of gametophytes shifts cultures to an exclusively male pattern after a dramatic suppression of growth. Mating experiments revealed that all populations are interfertile, although fertility was highest when the test Idaho population underwent intergametophytic‐selfing. The Idaho population evidenced a low level of genetic load consistent with predictions based on its sex expression. Although Olympic Peninsula populations evidenced apparent high genetic load in some experiments, failure to produce abundant sporophytes in other experiments suggested that additional cultural factors operated to reduce sporophyte formation. Moderate density mating experiments produced single sporophytes that were comparable to field collections. Isolated gametophytes underwent polyembryony after a time delay and gametophyte proliferation. Cultural conditions which allow sporophyte formation on isolated gametophytes without this delay or proliferation must be sought before further genetic analysis is undertaken.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06204.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Cluster analysis by four methods, ordination by principal component analysis (PCA) and simulation of evolutionary trees (Wagner Trees) were performed on morphological data from 43 characters of eight species of the South American genusBulnesia(Zygophyllaceae). The results of cluster analysis and principal component analysis in general agree and show that there are three pairs of taxa that appear, or obviously are, closely related. These are the pairsB. arborea–B. carrapo, B. foliosa–B. schickendantziiandB. retama–B. chilensis. These methods also indicate that the southern speciesB. bonariensisoccupies an intermediate position between the pair of northern tropical species (B. arborea, B. carrapo)and the remaining southern species. From the beginning it was assumed that these three multifoliolate species with large flowers may be rather primitive. The Prim network indicates that these three species are closely related among themselves. Also in two of the three Wagner Trees they are placed in a group. In all casesB. sarmientoiis shown as the more remote and isolated of all species. It is regarded as a unique, specialized arboreal species showing extreme reduction in number of leaflets and carpels, leaf and flower size, etc. All graphic representations (Fig. 1–3) show the phenetic similarity or the close phylogenetic relationships of the pairsB. foliosa–B. schickendantziiandB. retama–B. chilensisto each other. These four species would represent a rather advanced group. The most xerophytic speciesB. retamaandB. chilensisare regarded as the most advanced taxa and the most specialized histophysiologically. These occupy extreme and distant positions in PCA diagrams and Prim network, and top positions in the Wagner Trees.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06205.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Anthers of inbred F44fertile (N) and cytoplasmic male‐sterile (T) corn plants (Zea maysL.) were compared cytologically. No differences between fertile and sterile anthers were observed in size and number of mitochondria or plastids until after the start of anther degeneration. A rapid division of mitochondria was observed, however, in the tapetum and sporogenous cells of both fertile and sterile anthers during early growth stages. This rapid increase in mitochondrial numbers per cell (some 20‐to 40‐fold) preceded tapetal breakdown in sterile anthers and did not occur in other anther cells or in plastids. Limited observations on the megagametophyte and nucellus revealed that mitochondria in ovules remain relatively constant in size and number during gametogenesis and do not undergo degeneration.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06206.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

An abundance of circumstantial evidence has led earlier workers to believe that apomixis was a common phenomenon in North AmericanCrataegus. However, direct proof was lacking. In this paper, working with accessions ofCrataegus pruinosa(Wendl.) K. Koch,sens. lat., a common and rather variable species of eastern North America, we present cytological proof of apomixis. This paper demonstrates the existence of apospory and documents the development of the aposporous embryo sac. Pseudogamy is inferred.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06207.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

An underground biomass profile and productivity study involved year‐long sampling programs in 18 stands of salt marsh plants in Georgia, Delaware, and Maine. As the result of the monthly or bimonthly marsh coring program three types of underground biomass profiles were found. In the first, the concentration of macro‐organic matter (MOM) was uniform with depth; the notable example of this type was creekbankSpartina alterniflorain the southern part of the coast. A second type had a high MOM concentration at the surface which decreased with depth. This, the most common type of profile, was exemplified bySpartina patens, S. alterniflorafrom the high marsh along the southern coast (Georgia), and creekbankS. alterniflorafrom the northern part of its range (Maine). The third type of profile was seen where a large rhizome mat developed 15–20 cm below the surface.Spartina cynosuroidesandPhragmites communiswere typical examples of this type of profile, resulting in a low biomass at the surface, a higher biomass somewhat below the surface, and a low concentration at depth. The annual maxima and minima of MOM biomass were used to calculate annual increments, which can be considered minimum annual production values. These productivity values ranged from a low of 80 g C/m2for creekheadS. alterniflorain Maine to a high of 1690 g C/m2forJuncus gerardiin Maine. The mean for all plant stands was 650 g C/m2. Since the average carbon content of the MOM was 35.3%, this corresponds to 1850 g dry weight/m2per year. As a measure of the relative activity of the total pool of macro‐organic material in the soil, turnover times were calculated by dividing the total macro‐organic matter by the annual increments. Within the MOM pool there are several components with turnover times varying from days to years. The turnover time for the entire pool ranged from 18 months in two Georgia salt marsh plant stands to 224 months for one in Maine. In the two instances where values for a species could be compared between Maine and Georgia, the turnover time was shorter at the more southerly site. These results can probably be attributed to slower microbial decay rates in the cooler climate. In Georgia and Maine where the turnover values for a species were determined for two elevations, the time was shorter at the lower elevation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06208.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The pollen morphology of eight species ofNigella(Ranunculaceae) was examined by scanning and transmission electron microscopy. The exomorphology of all species was identical: 3‐colpate, spinulose, and punctate, but thin sections revealed two structural patterns. The ektexine structure ofNigella integrifolia, consisting of thickened foot layer, columellae, and thin tectum, is typical for the family as well as the order Ranunculales in general. In contrast, the remaining seven species,N. arvensis, N. damascena, N. elata, N. hispanica, N. sativa, N. segetalis, andN. stellaris, have an ektexine with an additional unit, a horizontal layer with shorter columellae, placed between the foot layer and tectum. Of all genera examined in the Ranunculaceae, onlyNigellahad this unusual stratification. This difference in the exine structure would add support to the treatment ofN. integrifoliaas a monotypic genus,Komaroffia integrifolia(Regel) Lemos Pereira.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06209.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Fifty‐seven Iranian collections ofHordeum violaceumBoiss.&Huet, a perennial forage grass, contained diploid (2n= 14), tetraploid (2n= 28), and hexaploid (2n= 42) chromosome races. All collections came from moderate to high elevations in the Alborz and Zagros mountains and adjacent plateau areas of Iran. Each chromosome race had a discrete distribution, and the hexaploids were the most widespread. The diploids were cytologically regular, except for a chromosome interchange that occurred in about half of the plants. The tetraploids and hexaploids behaved cytologically as autopolyploids. The hexaploids were taller, coarser and later‐flowering than the diploids and tetraploids, and they had fewer but thicker culms and larger seeds. The tetraploids were the leafiest and most productive, making them the most desirable from an agronomic standpoint. All races were more or less self‐sterile, a characteristic that setsH. violaceumapart from most otherHordeumspecies. The taxonomic status ofH. violaceumand its closest relatives,H. turkestanicumNevski andH. brevisubulatumLink, is uncertain because of close morphological similarities and the occurrence of chromosome races in each taxon.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06210.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Original chromosome counts are reported from 91 populations and 73 taxa distributed among 46 genera. Most of these were obtained from meiotic material and are first reports. Some of the more interesting counts are from genera with amphitropical distributions such asGaillardiaandHelenium. When appropriate, systematic implications of the data are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06211.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The premitotic rhizoid stage (corona stage) ofP. vittatagametophytes was pulsed in radioactive uridine for 5, 15, or 30 min and the data analyzed quantitatively by autoradiography. After 5 min, only the nucleoplasmic compartment is labelled significantly, suggesting that this short pulse is insufficient time for labelled precursor to be fixed in the nucleolus or to be transported from the nucleus to the cytoplasm. Since after 15 and 30 min, all compartments are labelled, with the greatest proportional increase over the nucleolus, it is concluded that cytoplasmic labelling is nuclear in origin and that nucleolar RNA activity is relatively high in this stage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06212.x

出版商:Wiley    

年代:1979

数据来源: WILEY