Morphology of the Crease Region in Relation to Assimilate Uptake and Water Loss During Caryopsis Development in Barley and Wheat

1983 ◽  
Vol 10 (6) ◽  
pp. 473 ◽  
Author(s):  
MP Cochrane
Keyword(s):  
Water Loss ◽  
Grain Filling ◽  
Wall Material ◽  
Wall Structure ◽  
Primary Wall ◽  
Xylem Parenchyma ◽  
Filling Water ◽  
Phenolic Substances ◽  
Electron Lucent ◽  
Days After Anthesis

Changes take place about 35 'days' after anthesis in the wall structure of the chalazal cells in caryopses of barley cv. Midas and wheat cv. Sicco grown in conditions where the number of 'days' from anthesis to harvest-ripeness is 60. The primary wall becomes lignified and is separated from the symplast by a layer of suberin. Massive deposits of electron-lucent wall material are laid down between the primary wall and the plasma membrane. From 15 'days' after anthesis increasing amounts of phenolic substances are found in the chalazal cell contents. Xylem parenchyma cells in the crease have some of the characteristics of gland cells and it is suggested that they may function in the control of the water content of the endospem. The cell wall modifications in the chalaza are interpreted as providing a means whereby, during the later stages of grain-filling, water loss from the endosperm can take place without interrupting the supply of assimilates to starchy endospem cells.

Ultrastructural observations on Helvellaceae (Pezizales, Ascomycetes). IV. Ascospore ontogeny in selected species of Gyromitra subgenus Discina

1990 ◽  
Vol 68 (2) ◽  
pp. 317-328 ◽  
Author(s):  
James W. Kimbrough ◽  
Chi-Guang Wu ◽  
Jack L. Gibson
Keyword(s):  
Key Words ◽  
Secondary Wall ◽  
Spore Wall ◽  
Wall Material ◽  
Wall Structure ◽  
Primary Wall ◽  
Spore Ornamentation ◽  
Wall Formation ◽  
Secondary Wall Formation ◽  
Definition Of

The ultrastructure of ascospore ontogeny and spore wall microchemistry are described in three sessile, discoid species of Gyromitra previously placed in Discina. Silver proteinate and barium permanganate were used as poststains to enhance the definition of various wall layers and spore organelles. Early stages of ascosporogenesis and primary wall formation are similar to those described in other species of Pezizales. Secondary wall formation, which results in characteristic spore ornamentation, is similar in Gyromitra brunnea, Gyromitra leucoxantha, and Gyromitra perlata. Mature spores of these species differ in the size and shape of translucent lacunae within the secondary wall, and in the morphology of apiculi. The lacunae originate through blebbing of primary wall material through the epispore into the secondary wall, resulting in the isolation of electron-translucent primary wall clumps within the electron-dense secondary wall. These and other ultrastructural observations of apothecial tissues support the maintenance of the Helvellaceae (sensu lato) to include taxa of the tribes Helvelleae, Discineae, and Rhizineae. Phylogenetic linkages of these taxa to other families of Pezizales are suggested. Key words: ascosporogenesis, ascospore wall structure and microchemistry, discomycete systematics and phylogeny.

scholarly journals Cell wall biosynthesis and the molecular mechanism of plant enlargement

2009 ◽  
Vol 36 (5) ◽  
pp. 383 ◽  
Author(s):  
John S. Boyer
Keyword(s):  
Cell Wall ◽  
Critical Level ◽  
Turgor Pressure ◽  
Chara Corallina ◽  
Wall Material ◽  
Primary Wall ◽  
Terrestrial Plants ◽  
Green Plants ◽  
Wall Deposition ◽  
Wall Growth

Recently discovered reactions allow the green alga Chara corallina (Klien ex. Willd., em. R.D.W.) to grow well without the benefit of xyloglucan or rhamnogalactan II in its cell wall. Growth rates are controlled by polygalacturonic acid (pectate) bound with calcium in the primary wall, and the reactions remove calcium from these bonds when new pectate is supplied. The removal appears to occur preferentially in bonds distorted by wall tension produced by the turgor pressure (P). The loss of calcium accelerates irreversible wall extension if P is above a critical level. The new pectate (now calcium pectate) then binds to the wall and decelerates wall extension, depositing new wall material on and within the old wall. Together, these reactions create a non-enzymatic but stoichiometric link between wall growth and wall deposition. In green plants, pectate is one of the most conserved components of the primary wall, and it is therefore proposed that the acceleration-deceleration-wall deposition reactions are of wide occurrence likely to underlie growth in virtually all green plants. C. corallina is one of the closest relatives of the progenitors of terrestrial plants, and this review focuses on the pectate reactions and how they may fit existing theories of plant growth.

Observations with cytochemistry and ultracryotomy on the fine structure of the expanding walls in actively elongating plant cells

1975 ◽  
Vol 19 (2) ◽  
pp. 239-259
Author(s):  
J.C. Roland ◽  
B. Vian ◽  
D. Reis
Keyword(s):  
Fine Structure ◽  
Periodic Acid ◽  
Middle Lamella ◽  
Positive Control ◽  
Apium Graveolens ◽  
Wall Structure ◽  
Primary Wall ◽  
Environmental Signals ◽  
3 Dimensional ◽  
Complementary Techniques

Ultracryotomy with negative staining and cytochemistry (periodic acid - thiocarbohydrazide - silver proteinate test for polysaccharides, in conjunction with mild extractions) were used to study the architecture of the cell wall and its modifications during expansion. Those techniques were applied to the study in situ of the walls of actively elongating parenchyma of mung bean (Phaseolus aureus), and pea (Pisum sativum) root and of collenchyma of celery (Apium graveolens) petioles. These complementary techniques provide information on the 3-dimensional disposition and fine structure of the subunits of the wall. In all the examples examined, the bulk of growing primary wall appears well-ordered and no progressive evolution from a transverse texture near the plasmalemma to a scattered texture near the middle lamella was observed. It seems unlikely that the development of the wall structure in relation to growth could be explained mechanically by a passive shift of the fibrillar elements in response to cellular stress. There is no evidence for an inert change in fibrillar orientation in the major part of the wall. If such occurs the process is limited to the outermost and senescent part of the wall. Thus, the texture observed does not agree with the classical multinet growth hypothesis but rather with the idea of an ordered structure of the primary wall. With the latter, the components should be able to respond in different ways to specific growth regulators and other environmental signals and thus exert a more positive control over the processes of oriented cell growth.

Corrigendum - Effects of a water stress on the photosynthesis and respiration of wheat ears

1980 ◽  
Vol 31 (5) ◽  
pp. 857
Author(s):  
B Marshall ◽  
RH Sedgley ◽  
PV Biscoe
Keyword(s):  
Carbon Dioxide ◽  
Water Stress ◽  
Maximum Rate ◽  
Dark Respiration ◽  
Light Response ◽  
Grain Filling ◽  
Response Curves ◽  
Rectangular Hyperbola ◽  
Wheat Leaves ◽  
Days After Anthesis

An experiment was conducted on Huntsman winter wheat to investigate the effects of a water stress applied at anthesis on the carbon dioxide exchange of the ears during grain filling. The water stress was created by excluding rain from the soil, not the foliage, of plants growing in the field. Control plants were well watered throughout the period when the treatment was imposed. At intervals for 32 days after anthesis, detailed measurements were made of the photosynthetic rate of ears at different irradiances and rates of ear dark respiration. The measurements were analysed by using the photosynthesis-light response model developed by Marshall and Biscoe (1980) for wheat leaves with a modification for the pathway of respiration from the grains to the glumes. The model is a non-rectangular hyperbola and uses four parameters: Pn,max (maximum rate of net photosynthesis), Rd (rate of dark respiration), � (photochemical efficiency at low light), and F (ratio of physical to total resistance to diffusion of carbon dioxide). Analysis showed that in wheat ears during grain filling, photosynthesis can be treated as occurring predominantly in the glumes and respiration in the grains. The shape of the photosynthesis-light response curves for ears from both treatments were similar, but differed from those for wheat leaves because the maximum rates of photosynthesis were reached more gradually with increasing irradiance. However, the measured response curves were still better fitted by the model than a rectangular hyperbola which has often been used in the past. The water stress at anthesis decreased the maximum rate of ear photosynthesis by 0.8 g carbon dioxide m-2 h-1 throughout the grain-filling period. Initially, the rates of ear respiration were the same, but 32 days after anthesis the treatment had decreased ear respiration rate from 0.04 to 0.01 g carbon dioxide h-1/grain.

Evaporation of Gravity- and Gas Flow-Driven Thin Liquid Films in Micro- and Minigrooves

2004 ◽  
Author(s):  
T. Gambaryan-Roisman ◽  
P. Stephan
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Gas Flow ◽  
Thin Liquid Film ◽  
Flow Region ◽  
Wave Theory ◽  
Liquid Films ◽  
Wall Material ◽  
Wall Structure ◽  
Ultra Thin Film

Using microstructured wall surfaces may improve the heat transfer performance of falling film or shear-driven film cooling devices enormously. The advantages of the structured surface include the prevention of the formation of dry patches on hot surfaces, the promotion of ultra-thin film evaporation, and a wavy motion of the film that enhances mixing of the liquid. We develop a model describing the hydrodynamics and heat transfer by evaporation of gravity- and gas flow-driven liquid films on grooved surfaces. For low Reynolds numbers or low liquid mass fluxes the heat transfer is governed by the evaporation of the ultra-thin film at a micro region, in the vicinity of the three-phase contact line. We investigate the hydrodynamic stability of the film flow using the long-wave theory. In addition to the films completely covering the wall structure, we study the stability characteristics of a thin liquid film partly covering the grooved wall, so that the flow region is bounded by contact lines. Two cases are analyzed: fully wetting liquids and liquids which form a small but finite contact angle with the wall material.

scholarly journals The Cell Wall Structure of Xylem Parenchyma

1952 ◽  
Vol 5 (2) ◽  
pp. 223 ◽  
Author(s):  
AB Wardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Secondary Cell Wall ◽  
Primary Cell Wall ◽  
Wall Structure ◽  
Xylem Parenchyma ◽  
Cell Axis ◽  
X Ray ◽  
Ray Methods ◽  
Longitudinal Cell

The fine structure of the cell wall of both ray and vertical parenchyma has been investigated. In all species examined secondary thickening had occurred. In the primary cell wall the micellar orientation was approximately trans"erse to the longitudiJ)aI cell axis. Using optical and X-ray methods the secondary cell wall was shown to possess a helical micellar organization, the micelles being inclined between 30� and 60� to the longitudinal cell axis.

Azygosporogenesis in Mucor azygosporus

1977 ◽  
Vol 55 (21) ◽  
pp. 2712-2720 ◽  
Author(s):  
K. L. O'Donnell ◽  
J. J. Ellis ◽  
C. W. Hesseltine ◽  
G. R. Hooper
Keyword(s):  
Wall Material ◽  
Primary Wall ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Outer Primary ◽  
Structural Aspects ◽  
Cytoplasmic Continuity

Light microscopic and scanning and transmission electron microscopic observations were obtained on azygosporogenesis in Mucor azygosporus Benjamin. Terminal gametangia are delimited by centripetally growing septa but plasmodesmata maintain cytoplasmic continuity between the azygophores and gametangia. Warts develop as regularly spaced patches of electron-opaque wall material on, and ultimately within, the inner primary wall. The mature complex azygosporangium wall is composed of (1) remnants of the membranous outer primary wall, (2) the ornamented layer of electron-opaque, stellate, confluent warts, and (3) a fibrillar, electron-opaque, tertiary layer. A homogeneous, hyaline azygospore wall (quaternary layer or endospore) with stellate warts is laid down within the azygosporangium. A comparison of the fine structural aspects of zygosporogenesis and azygosporogenesis in the Mucorales is presented.

scholarly journals (472) Yeast Expressed Tomato β-Galactosidases 1, 4, and 5 Have Activity against Synthetic and Plant-derived Cell Wall Substrates

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1092B-1092 ◽  
Author(s):  
Megumi Ishimaru ◽  
David L. Smith ◽  
Kenneth C. Gross
Keyword(s):  
Cell Wall ◽  
Tomato Fruit ◽  
Wall Material ◽  
Wall Structure ◽  
Fruit Softening ◽  
Pectic Polysaccharides ◽  
Wide Range ◽  
Fruit Pericarp ◽  
Galactosyl Residues

Fruit softening occurs by several mechanisms, including modifications of cell wall structure by wall degrading enzymes. The most prominent change in tomato fruit pericarp wall composition is the loss of galactosyl residues throughout development and especially during ripening. In order to understand the role of galactosyl turnover in fruit softening, we successfully produced three recombinant tomato β-galactosidase/exo-galactanase (TBG) fusion proteins in yeast. TBG1, 4 and 5 enzyme properties and substrate specificities were assessed. Optimum pH of TBG1, 4 and 5 was 5.0, 4.0, and 4.5 and optimum temperature was 40∼50, 40, and 40 °C, respectively. The K ms for TBG1, 4 and 5 were 7.99, 0.09, and 2.42 mm, respectively, using p-nitrophenyl-β-D-galactopyranoside as substrate. Using synthetic and plant-derived substrates, TBG1 and 5 released galactosyl residues from 1 → 4 linkages. TBG4 released galactosyl residues from a wide range of plant-derived oligosaccharides and polysaccharides. Using tomato fruit cell wall material, TBG1, TBG4 and TBG5 released galactosyl residues from a variety of fruit stages and cell wall fractions. TBG4 released the most galactosyl residues from the ASP fraction and especially the ASP fraction from fruit at the turning stage. Interestingly, even though walls from Turning fruit stage contain less total galactosyl residues than at the Mature Green stage, TBG4 released 3–4 fold more galactose from the CSP and ASP fractions from Turning fruit. These results suggest that changes in structure of wall pectic polysaccharides leading up to the Turning stage may cause the wall to become more susceptible to hydrolysis by the TBG4 product.

Effects of a water stress on the photosynthesis and respiration of wheat ears

1980 ◽  
Vol 31 (5) ◽  
pp. 857
Author(s):  
B Marshall ◽  
RH Sedgley ◽  
PV Biscoe
Keyword(s):  
Carbon Dioxide ◽  
Water Stress ◽  
Maximum Rate ◽  
Dark Respiration ◽  
Light Response ◽  
Grain Filling ◽  
Response Curves ◽  
Rectangular Hyperbola ◽  
Wheat Leaves ◽  
Days After Anthesis

An experiment was conducted on Huntsman winter wheat to investigate the effects of a water stress applied at anthesis on the carbon dioxide exchange of the ears during grain filling. The water stress was created by excluding rain from the soil, not the foliage, of plants growing in the field. Control plants were well watered throughout the period when the treatment was imposed. At intervals for 32 days after anthesis, detailed measurements were made of the photosynthetic rate of ears at different irradiances and rates of ear dark respiration. The measurements were analysed by using the photosynthesis-light response model developed by Marshall and Biscoe (1980) for wheat leaves with a modification for the pathway of respiration from the grains to the glumes. The model is a non-rectangular hyperbola and uses four parameters: Pn,max (maximum rate of net photosynthesis), Rd (rate of dark respiration), � (photochemical efficiency at low light), and F (ratio of physical to total resistance to diffusion of carbon dioxide). Analysis showed that in wheat ears during grain filling, photosynthesis can be treated as occurring predominantly in the glumes and respiration in the grains. The shape of the photosynthesis-light response curves for ears from both treatments were similar, but differed from those for wheat leaves because the maximum rates of photosynthesis were reached more gradually with increasing irradiance. However, the measured response curves were still better fitted by the model than a rectangular hyperbola which has often been used in the past. The water stress at anthesis decreased the maximum rate of ear photosynthesis by 0.8 g carbon dioxide m-2 h-1 throughout the grain-filling period. Initially, the rates of ear respiration were the same, but 32 days after anthesis the treatment had decreased ear respiration rate from 0.04 to 0.01 g carbon dioxide h-1/grain.

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