摘要:

The vascular system of the leaf ofPopulus deltoidesBartr. ex Marsh, was examined quantitatively, and plasmolytic studies were carried out to determine the solute concentrations of sieve‐tube members at various locations in the leaf. Both the total number and total crosssectional area of each cell type decreases with decreasing vein size. Although the proportion of phloem occupied by sieve tubes varies considerably from location to location, a linear relationship exists between cross‐sectional area of the vascular bundles and both total and mean cross‐sectional area of sieve tubes. Collectively, the cross‐sectional area of all tertiary and minor veins feeding into a secondary exceeds the total cross‐sectional area of sieve tubes at the base of that secondary. Moreover, the total volume of sieve tubes in the “catchment area” of a secondary vein is much greater than the total sieve tube volume of the secondary itself. Both tracheary elements and sieve‐tube members undergo a reduction in both total and mean crosssectional area in the constricted zone at the base of the leaf. The plasmolytic studies revealed the presence of positive concentration gradients in sieve tubes of the lamina from the minor veins and tips of the secondaries to the bases of the secondaries and their associated subjacent midvein bundles and from the upper to lower portions of the median bundle of the midvein.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08301.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

A new lyginopterid pollen organ is described based upon specimens occurring in a single coal ball from the Providence, Kentucky locality. Seven to nine beaked sporangia are fused together at their proximal ends forming a common synangial chamber; synangia are joined together in clusters of two or three. In situ prepollen is similar toCyclogranisporitesandVerrucosisporitessporae dispersae. The thick exine has a lamellate nexine and a prominent alveolate sexine.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08302.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The fate of the pine dwarf shoot (DS) apex after needle initiation has been controversial. Dwarf shoot primordia ofPinus longaevawere examined to determine the developmental basis for DS with and without interfoliar buds. Interfoliar buds are microscopic buds derived from the original terminal apex of the DS. In October, all the DS primordia are similar in size and appearance. However, as the needles elongate in the following June the apices of more proximal DS decrease in size, such that by July there is a clear diminishing size gradient of apical domes in going from the most distal to the most proximal positions. The distal DSs start to form bud scales in July and have fully formed interfoliar buds by mid‐August. In contrast, those DS apices lacking protective bud scales at needle maturity become suberized and can never proliferate into long shoots. The distal placement of interfoliar buds may be due to a group effect, where each developing DS inhibits the more proximal DSs in the long shoot terminal bud.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08303.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The resprouting ability following cutting of the chaparral shrubBaccharis pilularisssp.consanguinea(DC) C. B. Wolf was investigated following the felling of individuals of various ages. Numbers of resprouts and resprout biomass were low in 1‐yr‐old shrubs, increased to a maximum in shrubs 3–4 yr old, and declined to zero in shrubs<8 yr old. Numbers of leaves produced were also lower in 1‐yr‐old shrubs. The results are interpreted on the basis of the internal origin of resprout buds and the increasing extent of the shrub's root system as it matures.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08304.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

This new species is based on a single semifusinized cone from the Late Cretaceous (Cenomanian) of New Jersey. The cone is flattened but essentially complete. It is 55 mm long and 8 by 13 mm in diam. Scale apices are thin, rounded, and entire, lacking evidence of an umbo or spine. The vascular cylinder of the cone axis is organized as a series of separate strands. The scale is made up of a basal portion that stands out nearly perpendicular to the cone axis and a sharply upturned distal portion. The bract base has a pronounced abaxial keel. Bract and scale traces diverge from the vascular cylinder of the cone axis separately from one another. A poorly developed interseminal ridge is present at the chalazal end of the seeds. An unusual feature of the cone is the presence of a trichome‐bearing epidermis on the cone axis, bract‐scale complex, and near the scale apex. Resin canals diverge into the bract‐scale complex abaxial to the scale trace with branches becoming adaxial to the scale trace outward. A number of features of the new species occur in cones ofAbies, Cedrus, Keteleeria, Larix, Picea, Pseudolarix, Pseudotsuga, andTsugaas well as in the extinct genusPseudoaraucaria. Features ofPinusare absent. This suggests thatPseudoaraucariamay have served as an ancestral source for modern genera other thanPinuswithPityostrobus pubescensrepresenting an evolutionary intermediate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08305.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Wind tunnel analyses ofSimmondsia chinensis(Link) Schneider or “jojoba” were conducted to quantify the behavior of airborne pollen grains around individual branches and leaves and near individual carpellate flowers. Field data (wind velocity) were used to ensure a correspondence between wind tunnel and natural conditions. Based upon the visualization of individual pollen grain trajectories, it is concluded that pollen deposition on stigmatic surfaces is influenced by large‐scale aerodynamic patterns, generated by foliage leaves, and small‐scale airflow patterns, formed around and by floral parts and stigmas. Leaves are seen to deflect airborne pollen grains into trajectories that can intersect ambient airflow at 90° angles, showering decumbent carpellate flowers with pollen. Similarly, flowers can deflect pollen upward and downwind, toward other flowers. The extent of floral bract and sepal recurvature is shown to influence the extent of pollen deposition by determining the characteristic airflow pattern around stigmas.Available evidence concerning the relatively recent evolutionary transition to anemophily inSimmondsiais interpreted within the context of morphological adaptations and exaptations favoring wind pollination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08306.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The pollen grain ofHymenocallis quitoensisHerb, is examined with scanning and transmission electron microscopy. The very large, monosulcate grain is characterized by a coarsely reticulate exine surface and solid, auriculate appendages at the equatorial facies. Surface morphology of the pollen grain ofH. quitoensisis compared with other representative species ofHymenocallisand supports the inclusion ofH. quitoensiswithin the genus. Meridional exine dimorphism in other species ofHymenocallisis interpreted as a reduction from the well‐defined auriculae ofH. quitoensis. Surface morphology of the pollen grain ofHymenocallissects.ArtemaTraub andElisena(Herb.) Traub exhibits divergence from that of sects.HymenocallisandIsmene(Herb.) Traub. Phylogenetic and paleobotanical implications of the auriculate pollen grain are briefly discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08307.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

The number of leaves on the main culm was correlated with morphological changes in the wheat spike during development, up to the terminal spikelet stage. The developmental changes were divided into nine stages, which were compared with stages described by other investigators. Several environmental conditions were utilized to determine the consistency of morphological correlations. Although the different environments did influence the length of time required to reach the various stages, the relationship between leaf number and stage of spike development was consistent. Regardless of environmental conditions, all stages were evident. Vernalization period affected the number of spikelets. Plants vernalized 6 wk produced 17–19 spikelets, compared to 21–24 spikelets on plants vernalized 3 wk. There were three major morphological events during spike development: 1) the change from vegetative to reproductive growth, 2) lateral spikelet development, and 3) the initiation and development of the terminal spikelet.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08308.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Four soybean (Glycine maxL. Merr.) lines isogenic except for loci controlling male sterility (ms1) and nodulation (rj1) were developed to study the effects of reproductive development and nitrogen source on the nucleic acid and protein levels within the leaves. Changes in DNA, RNA, protein, and cellular viability were measured from flowering (77 days after emergence) until maturity (147 days after emergence) in leaves of nodulated and non‐nodulated male‐sterile and fertile soybean genotypes. Leaf nuclei from the sterile genotypes yielded DNA amounts that were significantly higher than those from the fertile lines. The average DNA values for the nodulated sterile and nodulated fertile lines at 147 days after emergence were 7.01 and 2.45 picograms, respectively. The average 2C DNA amount as determined from dividing root‐tip nuclei was 2.83 picograms, which indicated occurrence of endopolyploid mechanisms in the sterile lines and age‐related loss of DNA in fertile lines. Similar to DNA findings, the RNA and protein values in the sterile lines were significantly higher than those values observed in the fertile lines, suggesting an increased capacity to synthesize protein. The soybean leaf nuclear DNA declined, especially in the fertile lines in terms of the percent endopolyploid nuclei as well as the average DNA content during maturation. The DNA decline in leaves of fertile genotypes suggests that the leaves may be exporting nucleosides and phosphates to the seeds during embryo formation. In the sterile lines, due to the reduced pod‐set, these ready reserves of nucleosides and phosphates tended to accumulate in the chromatin of the leaf nucleus as manifested by the DNA specific Feulgen stain.By the end of the study (147 days after emergence), the nodulated fertile genotypes had experienced a dramatic loss in DNA, RNA, and protein. The nodulated sterile genotypes, however, indicated 65% more DNA, 59% more RNA, and 53% more protein as compared to the nodulated fertile genotypes at 147 days after emergence. The sterile lines also indicated the slowest increase in the death of cells, while the fertile lines indicated the fastest increase in nonviable cells, as shown by trypan blue staining. The fertile lines displayed normal monocarpic senescence throughout the study. The reproductive structures of fertile plants utilized the molecules in seed production, whereas in the sterile lines, these accumulated in leaf cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08309.x

出版商:Wiley    

年代:1985

数据来源: WILEY

摘要:

Tissue concentrations of 12 mineral elements (Al, Ca, Cu, Fe, K, Mg, Mn, amino‐N, Na, P, Si, and Zn) were measured in an autoparasitic mistletoe (Phoradendron californicum), the parasitic mistletoe on which it was growing (Phoradendron californicum), and the host tree (Cercidium floridum). Mineral concentrations in the autoparasite were typically 1.1–1.3 times higher than in the parasite. Mineral concentrations of all elements except Ca, Fe, Mg, Mn, and Si were higher in the parasitic mistletoe than its host. Mineral concentration differences are discussed relative to accumulation via the transpiration stream and translocation within the host via the phloem.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1985.tb08310.x

出版商:Wiley    

年代:1985

数据来源: WILEY