Another View of the Ultrastructure of Cucurbita Phloem

Evert, Ray F.; Murmanis, Lidija; Sachs, Irving B.

doi:10.1093/oxfordjournals.aob.a084097

Cited by 58 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This particular phenomenon does not strictly separate the sieve elements with dispersing and nondispersing P-protein bodies. The displacement of P-protein bodies toward the sieve plates may occur in sieve elements with the usual ontogeny of the P-protein bodies (e.g., see references 2,8). The dispersal or nondispersal of the P-protein bodies can be related to the position of the sieve elements in the complex phloem system of Cucurbita.…”

Section: Discussionmentioning

confidence: 99%

P PROTEIN IN THE PHLOEM OF CUCURBITA

Cronshaw

Esau

1968

The Journal of Cell Biology

View full text Add to dashboard Cite

During maturation of sieve elements in Cucurbita maxima Duchesne, the P-protein bodies (slime bodies) usually disperse in the tonoplast-free cell. In some sieve elements the P-protein bodies fail to disperse. The occurrence of dispersal or nondispersal of P-protein bodies can be related to the position of the sieve elements in the stem or petiole. In the sieve elements within the vascular bundle the bodies normally disperse; in the extrafascicular sieve elements the bodies often fail to disperse. Extrafascicular sieve elements showing partial dispersal also occur. The appearance of the sieve plate in fixed material is related to the degree of dispersal or nondispersal of the P-protein bodies. In sieve elements in which complete dispersal occurs the sieve plate usually has a substantial deposit of callose, and the sieve-plate pores are filled with P protein. In sieve elements containing nondispersing P-protein bodies the sieve plate bears little or no callose, and its pores usually are essentially "open." The dispersed P-protein components may aggregate into loosely organized "strands," which sometimes extend vertically through the cell and continue through the sieve-plate pores; but they may be oriented otherwise in the cell, even transversely.

show abstract

Section: Discussionmentioning

confidence: 99%

P PROTEIN IN THE PHLOEM OF CUCURBITA

Cronshaw

Esau

1968

The Journal of Cell Biology

View full text Add to dashboard Cite

show abstract

“…However, callose formation during pore development may nonetheless be important in determining the flow characteristics of the pore. Some authors have noted that deposition of callose on the face of the end wall where the pore will form is associated with the cessation of wall thickening at that point, so that in the mature sieve plate, the pore openings are in slight depressions in the face of the wall (Evert et al, 1966;Deshpande, 1974Deshpande, , 1975. It is proposed that callose actually restricts wall growth.…”

Section: The Callose Lining May Determine the Flow Characteristics Ofmentioning

confidence: 99%

“…Others reject the idea that callose replaces original cell wall material and propose that pore formation involves degradation of the original material as well as some callose. According to this view, the main function of callose deposition is to restrict wall thickening in the region in which the pore will form (Evert et al, 1966;Deshpande, 1974Deshpande, , 1975.…”

mentioning

confidence: 99%

Callose Synthase GSL7 Is Necessary for Normal Phloem Transport and Inflorescence Growth in Arabidopsis

et al. 2010

View full text Add to dashboard Cite

One isoform of callose synthase, Glucan Synthase-Like7 (GSL7), is tightly coexpressed with two isoforms of sucrose synthase (SUS5 and SUS6) known to be confined to phloem sieve elements in Arabidopsis (Arabidopsis thaliana). Investigation of the phenotype of gsl7 mutants of Arabidopsis revealed that the sieve plate pores of stems and roots lack the callose lining seen in wild-type plants. Callose synthesis in other tissues of the plant appears to be unaffected. Although gsl7 plants show only minor phenotypic alterations during vegetative growth, flowering stems are reduced in height and all floral parts are smaller than those of wild-type plants. Several lines of evidence suggest that the reduced growth of the inflorescence is a result of carbohydrate starvation. Levels of sucrose, hexoses, and starch are lower in the terminal bud clusters of gsl7 than in those of wild-type plants. Transcript levels of "starvation" genes expressed in response to low sugars are elevated in the terminal bud clusters of gsl7 plants, at the end of the night, and during an extended night. Pulse-chase experiments with 14 CO 2 show that transport of assimilate in the flowering stem is much slower in gsl7 mutants than in wild-type plants. We suggest that the callose lining of sieve plate pores is essential for normal phloem transport because it confers favorable flow characteristics on the pores.

show abstract

“…Specific solute transporters mediate SE composition (for review, see Lalonde et al, 2003;Sauer, 2007), and their specificities and patterns of expression ensure a qualitative control on the phloem sap composition of a particular sieve tube (ST). Sap exchange between adjacent STs in a vascular bundle, however, is possible, as lateral sieve areas have been observed in angiosperms (Esau and Cheadle, 1959;Evert et al, 1966;Walsh and Melaragno, 1976), and osmolytes can also be exchanged between SEs by unloading and subsequent reloading of the SE (Thorpe and Minchin, 1987). The composition of phloem sap is not constant and can vary between day and night, for example, in barley (Hordeum vulgare; Winter et al, 1992), grapevine (Vitis vinifera; Gholami et al, 2004), and Ricinus (Smith and Milburn, 1980).…”

mentioning

confidence: 99%

A Diurnal Component to the Variation in Sieve Tube Amino Acid Content in Wheat

et al. 2008

View full text Add to dashboard Cite

We have used high-sensitivity capillary electrophoresis coupled to a laser-induced fluorescence detection method to quantify 16 amino acids in wheat (Triticum aestivum) sieve tube (ST) samples as small as 2 nL collected by severing the stylets of feeding aphids. The sensitivity of the method was sufficient to determine a quantitative amino acid profile of individual STs without the need to bulk samples to produce larger volumes for analysis. This allowed the observation of the full range of variation that exists in individual STs. Some of the total concentrations of amino acids recorded are higher than those reported previously. The results obtained show variation in the concentrations of phenylalanine (Phe), histidine/valine (His/Val), leucine/ isoleucine (Leu/Ile), arginine, asparagine, glutamine, tyrosine (Tyr), and lysine (Lys) across the ST samples. These could not be explained by plant-to-plant variation. Statistical analyses revealed five analytes (Tyr, Lys, Phe, His/Val, and Leu/Ile) that showed striking covariation in their concentrations across ST samples. A regression analysis revealed a significant relationship between the concentrations of Tyr, Lys, Phe, Leu/Ile, His/Val, asparagine, arginine, and proline and the time of collection of ST samples, with these amino acids increasing in concentration during the afternoon. This increase was confirmed to occur in individual STs by analyzing samples obtained from stylet bundles exuding for many hours. Finally, an apparent relationship between the exudation rate of ST sap and its total amino acid concentration was observed: samples containing higher total amino acid concentrations were observed to exude from the severed stylet bundles more slowly.

show abstract

Another View of the Ultrastructure of Cucurbita Phloem

Cited by 58 publications

References 0 publications

P PROTEIN IN THE PHLOEM OF CUCURBITA

P PROTEIN IN THE PHLOEM OF CUCURBITA

Callose Synthase GSL7 Is Necessary for Normal Phloem Transport and Inflorescence Growth in Arabidopsis

A Diurnal Component to the Variation in Sieve Tube Amino Acid Content in Wheat

Contact Info

Product

Resources

About