Ovule and seed development in Pinus radiata: postmeiotic development, fertilization, and embryogeny

1976 ◽  
Vol 54 (18) ◽  
pp. 2141-2154 ◽  
Author(s):  
Barbara S. Lill
Keyword(s):  
Seed Development ◽  
Pinus Radiata ◽  
Vascular Tissue ◽  
Small Cells ◽  
Dense Cytoplasm ◽  
Procambial Strand ◽  
Embryo Maturity

Development of ovule tissues in Pinus radiata after meiosis, fertilization, and embryogeny is comparable with that of other pines, but P. radiata takes longer to develop. Fertilization occurs 15 months after pollination and morphological embryo maturity is reached 5 months later. In ovules harvested in spring after meiosis, a curved band of small cells with dense cytoplasm extends from the chalazal end of the ovule to the vascular tissue of the ovuliferous scale. It is interpreted as a procambial strand, which in the next year, differentiates basipetally into elongated, thick-walled cells with degenerated nuclei.

The opening and shedding mechanism of the female cones of Pinus radiata

1964 ◽  
Vol 12 (2) ◽  
pp. 125 ◽  
Author(s):  
R Allen ◽  
AB Wardrop
Keyword(s):  
Pinus Radiata ◽  
Radial Growth ◽  
Secondary Wall ◽  
Vascular Tissue ◽  
Middle Layer ◽  
Cell Axis ◽  
Vascular Connection ◽  
Differential Shrinkage ◽  
Longitudinal Cell ◽  
Cone Scale

The opening of the female cones of P. radiata has been shown to result from differential shrinkage between the adaxial vascular tissue and the abaxial sclerenchyma of the cone scale. The organization of the secondary wall of the tracheids typically consists of three helically organized concentric layers. In the outer and inner layers the microfibrillar orientation is approximately transverse, and in the middle layer the helix makes an angle of c. 40° with the longitudinal cell axis. In the sclerenchyma the secondary wall consists of wide layers in which the microfibrils of the lamellae are almost transverse to the longitudinal cell axis, alternating with narrow layers in which the microfibrils of the lamellae are almost parallel to the cell axis. Opening is preceded by a severance of the vascular connection between the cone and the stem or branch by the occlusion of the lurnina of the tracheids of the peduncle with resin. As radial growth of the stem proceeds, small fissures develop between the xylem of the stem or branch and that of the cone peduncle. The fissures become filled with resin and there is a progressive erosion of the tracheids of the peduncle until ultimately the xylem of the peduncle is separated from that of the stem or branch.

True dichotomies in seedlings of Pinus radiata

1976 ◽  
Vol 54 (9) ◽  
pp. 1020-1022
Author(s):  
Richard T. Riding
Keyword(s):  
Shoot Apex ◽  
Pinus Radiata ◽  
Vascular Tissue

Histological observations of bifurcating seedlings of Pinus radiata revealed that this phenomenon resulted from a dichotomy of the shoot apex into two meristems. Vascular tissue passed equally into the two branches of the dichotomy.

Improving initiation, genotype capture, and family representation in somatic embryogenesis of Pinus radiata by a combination of zygotic embryo maturity, media, and explant preparation

2009 ◽  
Vol 39 (8) ◽  
pp. 1566-1574 ◽  
Author(s):  
Cathy L. Hargreaves ◽  
Cathie B. Reeves ◽  
Jens I. Find ◽  
Keiko Gough ◽  
Puthiyaparambil Josekutty ◽  
...  
Keyword(s):  
Somatic Embryogenesis ◽  
Pinus Radiata ◽  
Zygotic Embryo ◽  
Embryogenic Tissue ◽  
Zygotic Embryos ◽  
Embryogenic Tissues ◽  
Preparation Techniques ◽  
Embryo Maturity ◽  
Collection Time ◽  
Excised Embryos

The principal aim of this investigation was to improve somatic embryogenesis initiation and to enhance representation of families and genotypes within those families of Pinus radiata D. Don. A total of 19 open-pollinated seed families, many with unrelated and weakly related parents, were tested. Optimum stage of cone maturity for initiation success was tested by five collections made at 1 week intervals, spanning the developmental period from pro-embryo to cotyledonary embryos. Two media were compared; embryo-development media (EDM6) and a modified Litvay medium (Glitz). Two zygotic embryo explant-preparation techniques were tested; embryos with retained megagametophytes and excised embryos. Proliferating embryogenic tissues were obtained from all four treatments (2850 explants per treatment, 570 per collection time) for the 19 families. The best initiation rates were achieved with a combination of Glitz medium with excised zygotic embryos, with 55% of explants from all collections and all families combined giving rise to proliferating embryogenic tissue. At the optimal collection time for each of the families, this treatment gave a range of 47%–97% initiation success with an average of 70% per family.

Floral development of Alisma triviale

1972 ◽  
Vol 50 (3) ◽  
pp. 619-627 ◽  
Author(s):  
V. Singh ◽  
R. Sattler
Keyword(s):  
Floral Development ◽  
Vascular Tissue ◽  
Radial Symmetry ◽  
Early Growth ◽  
Stages Of Development ◽  
The Third ◽  
Lack Of Fusion ◽  
Stamen Primordia ◽  
Procambial Strand ◽  
The Many

The primordia of the floral appendages are initiated in acropetal order. They develop in the same order in which they appear but for the petals, which are retarded in their early growth and mature rapidly shortly before anthesis. While the sepal primordia are dorsiventral from their inception, the primordia of other appendages are of nearly radial symmetry and become more or less dorsiventral in their later stages of development. Each petal primordium together with the primordia of a stamen pair arise on one common petal–stamen (CA) primordium. The many pistil primordia arise on three antesepalous gynoecial bulges and the area between them. Thus, in its development the flower exhibits primarily a tricyclic trimerous plan. The floral apices have a two-layered tunica up to the stage of pistil inception. The initiation of all floral appendages occurs by periclinal divisions in the second layer. The third layer (corpus) may contribute, especially in the case of the petal–stamen primordia and the gynoecial bulges. The development of procambium is acropetal. Each primordium receives a single procambial strand shortly after its initiation. Thus, procambial differentiation occurs as a response to primordial inception and not according to the principle of the conservatism of vascular tissue. Additional procambial strands may differentiate as a response to increase in size. The relationships of Alisma to some ranalian families are discussed. Since the floral pattern of Alisma may be considered as a secondary derivation from a trimerous pattern, it does not appear primitive at all. Other primitive features such as apocarpy and lack of fusion of pistil margins are however retained. Thus, Alisma is a good example for heterobathmy.

Floral nectar production in Helleborus foetidus: an ultrastructural study

Botany ◽  
2012 ◽  
Vol 90 (12) ◽  
pp. 1308-1315 ◽  
Author(s):  
J.L. Vesprini ◽  
E. Pacini ◽  
M. Nepi
Keyword(s):  
Cell Wall ◽  
Vascular Tissue ◽  
Proximal Part ◽  
Amorphous Structure ◽  
Small Cells ◽  
Outer Cell ◽  
Basal Region ◽  
Floral Nectar ◽  
Nectar Production ◽  
Helleborus Foetidus

The floral nectaries of Helleborus foetidus L. were studied using scanning and transmission electron microscopy, as well as light microscopy. Nectaries are tubular and consist of an external epidermis, a photosynthesizing parenchyma, large branches of vascular tissue, a nectar-producing parenchyma, and an internal epidermis. The external epidermis is characterized by thick outer walls and a thin cuticle. Cells of the photosynthesizing parenchyma are characterized by chloroamyloplasts. The nectar-producing parenchyma consists of small cells with lobed nucleus, several small vacuoles, and numerous undifferentiated elongated plastids. These cells contain lipid bodies, Golgi membranes, and rough endoplasmic reticulum and are connected by numerous plasmodesmata. Parenchyma cells around sieve elements contain some amyloplasts. The outer cell wall of the internal epidermis displays a central thinned area containing a depression. The cuticle is very thick with amorphous structure, especially evident in its proximal part. Secretion takes place only in the inner basal region of the nectary cup. The surface of the internal epidermis is devoid of secreting structures. Nectar is released by fracture of the cuticle and underlying cell wall; however, epidermal cell death is not apoptotic. This holocrine secretion is coupled with a more common merocrine secretion through which nectar accumulates in subcuticular spaces. This combined secretion mode produces an enriched “nectar soup” crucial for interactions with pollinators and yeasts during winter flowering.

Comparison of Choriocarcinoma and Normal Placenta

1971 ◽  
Vol 29 ◽  
pp. 324-325
Author(s):  
John C. Garancis ◽  
Roland A. Pattillo ◽  
Robert O. Hussa ◽  
Jon V. Straumfjord
Keyword(s):  
Cell Lines ◽  
Small Cells ◽  
Tissue Cultures ◽  
Glycogen Depletion ◽  
Cell Surfaces ◽  
Intercellular Spaces ◽  
Concomitant Increase ◽  
Gestational Choriocarcinoma ◽  
Cytoplasmic Glycogen ◽  
Normal Placenta

Two different cell lines (Be-Wo and Jar) of human gestational choriocarcinoma have been maintained in continuous tissue culture for a period of four and two years respectively without losing the ability to elaborate human chorionic gonadotropin (HCG). Tissue cultures, as revealed by electron microscopy, consisted of small cells with single nuclei. In some instances cell surfaces were provided with microvilli but more often the intercellular spaces were narrow and bridged by desmosomes. However, syncytium was not formed. Endoplasmic reticulum (ER) was poorly developed in both cell lines, except in some Be-Wo cells it was prominent. Golgi complex, lysosomes and numerous free ribosomes, as well as excessive cytoplasmic glycogen, were present in all cells (Fig. 1). Glycogen depletion and concomitant increase of ER were observed in many cells following a single dose of 10 ugm/ml of adrenalin added to medium (Fig. 2).

Ineffective Thrombopoiesis

1990 ◽  
Vol 48 (3) ◽  
pp. 266-267
Author(s):  
JM Radley ◽  
SL Ellis
Keyword(s):  
Microscopic Examination ◽  
Phosphate Buffer ◽  
Primary Myelofibrosis ◽  
Transient Increase ◽  
Major Difficulty ◽  
Adult Mice ◽  
Dense Cytoplasm

In effective thrombopoies is has been inferred to occur in several disease sates from considerations of megakaryocyte mass and platelet kinetics. Microscopic examination has demonstrated increased numbers of megakaryocytes, with a typical forms particularly pronounced, in primary myelofibrosis. It has not been documented if megakaryocyte ever fail to reach maturity in non-pathological situations. A major difficulty of establishing this is that the number of megakaryocytes normally present in the marrow is extremely low. A large transient increase in megakaryocytopoiesis can how ever be induced in mice by an injection of 5-fluorouracil. We have utilised this treatment and report here evidence for in effective thrombopoies is in healthy mice.Adult mice were perfused (2% glutaraldehyde in 0.08M phosphate buffer, pH 7.4) 8 days following an injection of 5-fluorouracil (150mg/kg). Femurs were subsequently decalcified in 10% neutral E.D.T.A. and embedded in Spurrs resin. Transverse sections of marrow revealed many megakaryocytes at various stages of maturity. Occasional megakaryocytes (less than 1%) were found to be under going degeneration prior to achieving full maturation and releasing cytoplasm as platelets. These cells were characterized by a peripheral rim of dense cytoplasm which enveloped a mass of organelles and vacuoles (Fig. 1). Numerous microtubules were foundaround and with in the organelle-rich zone (Fig 2).

Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips

1980 ◽  
Vol 38 ◽  
pp. 798-799
Author(s):  
Patrick Echlin ◽  
Thomas Hayes ◽  
Clifford Lai ◽  
Greg Hook
Keyword(s):  
Vascular Tissue ◽  
Lemna Minor ◽  
Atomic Weight ◽  
Companion Cell ◽  
Root Tips ◽  
Phloem Tissue ◽  
Cell Stage ◽  
Phloem Parenchyma ◽  
Parenchyma Cells ◽  
Xylem Element

Studies (1—4) have shown that it is possible to distinguish different stages of phloem tissue differentiation in the developing roots of Lemna minor by examination in the transmission, scanning, and optical microscopes. A disorganized meristem, immediately behind the root-cap, gives rise to the vascular tissue, which consists of single central xylem element surrounded by a ring of phloem parenchyma cells. This ring of cells is first seen at the 4-5 cell stage, but increases to as many as 11 cells by repeated radial anticlinal divisions. At some point, usually at or shortly after the 8 cell stage, two phloem parenchyma cells located opposite each other on the ring of cells, undergo an unsynchronized, periclinal division to give rise to the sieve element and companion cell. Because of the limited number of cells involved, this developmental sequence offers a relatively simple system in which some of the factors underlying cell division and differentiation may be investigated, including the distribution of diffusible low atomic weight elements within individual cells of the phloem tissue.

Clinical aspects of reactive oxygen and nitrogen species

2004 ◽  
Vol 71 ◽  
pp. 121-133 ◽  
Author(s):  
Ascan Warnholtz ◽  
Maria Wendt ◽  
Michael August ◽  
Thomas Münzel
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Risk Factor ◽  
Endothelial Dysfunction ◽  
Vascular Tissue ◽  
Rapid Development ◽  
Reactive Oxygen ◽  
Clinical Aspects ◽  
No Production ◽  
Oxygen Species

Endothelial dysfunction in the setting of cardiovascular risk factors, such as hypercholesterolaemia, hypertension, diabetes mellitus and chronic smoking, as well as in the setting of heart failure, has been shown to be at least partly dependent on the production of reactive oxygen species in endothelial and/or smooth muscle cells and the adventitia, and the subsequent decrease in vascular bioavailability of NO. Superoxide-producing enzymes involved in increased oxidative stress within vascular tissue include NAD(P)H-oxidase, xanthine oxidase and endothelial nitric oxide synthase in an uncoupled state. Recent studies indicate that endothelial dysfunction of peripheral and coronary resistance and conductance vessels represents a strong and independent risk factor for future cardiovascular events. Ways to reduce endothelial dysfunction include risk-factor modification and treatment with substances that have been shown to reduce oxidative stress and, simultaneously, to stimulate endothelial NO production, such as inhibitors of angiotensin-converting enzyme or the statins. In contrast, in conditions where increased production of reactive oxygen species, such as superoxide, in vascular tissue is established, treatment with NO, e.g. via administration of nitroglycerin, results in a rapid development of endothelial dysfunction, which may worsen the prognosis in patients with established coronary artery disease.

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