摘要:

Ultrastructure in the symbiotic association inCornicularia normoerica, fixed in glutaraldehyde, was demonstrated by staining either with potassium permanganate or osmium tetroxide‐thiocarbohydrazide‐osmium tetroxide (OTO) procedures modified for lichen tissues. Channels were observed to originate within the chloroplast, cross the algal cell wall and flare to open space shared with fungal and other algal cells. Tubules within the channels were extensions of chloroplast vesicles. Deeply staining channel walls, tubule elements, spherical bodies within the chloroplast, and organelles of the fungal cytoplasm suggested lipoid substances. The OTO procedure delineated zones in the thick cell walls of both symbionts. Their exterior boundaries were without discernible cellular membranes. The inner zone of the fungal cell wall was finely layered and particulate. No invasive fungal haustoria or zones of dissolution between fungus and alga were seen in any preparation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07423.x

出版商:Wiley    

年代:1968

数据来源: WILEY

摘要:

The digestive gland of Venus's flytrap has been studied by light and electron microscopy. Cells of the gland contain dense protoplasm comprised of relatively large nuclei, granular endoplasmic reticulum, osmiophilic vacuolar inclusions and numerous mitochondria, Golgi bodies and plastids. The vacuolar inclusions are predominantly protein but are also sudanophilic, therefore containing some lipid material. They are similar in appearance to aleurone grains. The nuclear envelope is a porous, double‐membrane structure, the pores of which are approximately 900 A and have a dense granular appearance. Plastids contain dense fine‐grained stroma, several thylakoids, osmiophilic globules and a tubular complex. Gland cell walls have many complex‐shaped protuberances extending into the cytoplasm providing a very large internal surface area. The stalk and basal cells contain numerous lipid globules and the common wall between the two cells is traversed by numerous plasmodesmata. In general the digestive gland fine structure is discussed in relation to its function.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07424.x

出版商:Wiley    

年代:1968

数据来源: WILEY

摘要:

Cell fine structure of developing cotyledons and embryonic axes ofPhaseolus lunatusL. seeds was studied relative to stage of seed development and the ability of excised embryonic axes to grow and withstand desiccation. Two stages in the development of the seed were recognized: (a) a ripening stage, characterized by more rapid increase in dry weight than in fresh weight, resulting in a decrease in seed moisture to 60%, and (b) a maturation stage during which seeds lost water without increase in dry weight. Above 70% water, excised embryonic axes failed to grow. Complete potential for growth developed by the time the seed reached 55–50% water. The axes were able to grow before they developed the ability to withstand desiccation. In cells of the youngest axes the ribosomes tend to be grouped into polysome units which surround the endoplasmic reticulum. As the cells mature the polysomes disappear and free ribosomes appear in the cytoplasm. Mitochondria in young axes contain electron‐dense matrices and swollen cristae; with maturation the mitochondrial matrix becomes optically empty and the cristae less swollen. Chloroplasts in young cells contain grana which disappear as the seeds mature. Similar changes occur in the cells of cotyledons. The data suggest that changes in cell fine structure during maturation are not destructive changes caused by excessive loss of water, but they indicate physiological changes which may be necessary to prepare the cells to withstand desiccation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07425.x

出版商:Wiley    

年代:1968

数据来源: WILEY

摘要:

A cytogeographio survey of western AmericanRumex paucifoliusNutt. reveals that diploid (2n= 14) and tetraploid (2n= 28) populations occur within the Rocky Mountain var.paucifoliusand also within the California var.gracilescensRech. The meiotic behavior of the chromosomes, the occurrence of aneuploid individuals in the populations, and the occasional occurrence of higher polyploids in nature suggest that the tetraploids are substantially autopolyploid in origin. The two diploid populations are restricted in range and are known, respectively, from high elevations in the southern Sierra Nevada of California and the mountainous region at the headwaters of the Missouri River in Montana and Wyoming. They are patroendemics, for they represent the ancestral diploids from which the more abundant polyploids arose. Both the diploid and the tetraploid populations are dioecious. The available evidence supports the suggestion that sex determination follows an X/Y (Melandrium) scheme in inheritance, but no evidence of heteromorphic sex chromosomes was found.Rumex paucifoliusis cytologically and morphologically distinct from any other native North AmericanRumex. Its characters resemble theR. acetosellagroup of the subgenus Acetosella, as much as they resemble any known members of subgenus Acetosa. For this and other reasons, the subgenera Acetosa and Acetosella should be combined.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07426.x

出版商:Wiley    

年代:1968

数据来源: WILEY

摘要:

A living species of the fossil genusKakabekia, isolated from a soil sample secured at Harlech Castle, Wales, is described. It resembles the type speciesK. umbellataBarghoorn in all major respects: tripartite structure consisting of mantle, stiple and basal enlargement, and size range of 5–15 μ. Variations in the cultured form include mantle margin (entire to scalloped), mantle radial structure (6‐ to 8‐parted, but sometimes 5‐ to 9‐parted) and concentric rings. The nameK. barghoornianais proposed in recognition of the discoverer and author of the fossil genus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07427.x

出版商:Wiley    

年代:1968

数据来源: WILEY

摘要:

Observations are reported on the distribution and appearance of long‐ and short‐root apices of nursery seedlings and plantation trees. Only emerging lateral roots over 50% of the diameter of the mother roots become long‐roots, and only from 10 to 21% attain this initial size. Short‐roots have rounded apices with small, sharply delimited, hemispherical or lens‐shaped meristematic zones. Long‐roots have pointed apices with paraboloid‐shaped meristematic zones showing light‐absorbing zones near the apex as well as near the base of the paraboloid. In small‐diameter long‐roots, lateral short‐roots tend to be uniformly distributed throughout the increment, but in large‐diameter roots they are closer together at the two ends of the increment. Lateral roots may be missing completely in the largest‐diameter pioneer roots. Both long‐ and short‐roots are inhabited by various species of fungi, mycorrhizal and non‐mycorrhizal. The patterns of fungal distribution in long‐roots vary from the proximal to the distal ends of the seasonal growth increments, depending on root growth and morphology. Mycorrhizal‐forming fungal species appear to predominate during the growing season but non‐mycorrhizal species may become prominent during the dormant season. The reactivation of apical and lateral meristems following dormancy occurs somewhat in advance of growth resumption by the fungi. However, delay in growth of the fungi is usually not long enough to permit emerging laterals to escape infection from the developing Hartig net in the mother root. Very large first‐order laterals of 3–0 seedlings and large pioneer roots in the plantations may ultimately acquire a sufficiently rapid growth rate to escape the fungus. When this occurs lateral roots may be initiated from a fungal‐free zone in the mother root and may become infected later. A very sparse Hartig net suffices for a strong invasion of emerging laterals, because hyphal growth is stimulated in the vicinity of a developing lateral.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1968.tb07428.x

出版商:Wiley    

年代:1968

数据来源: WILEY