Plastid ultrastructures

Simkin AJ, Gaffe J, Alcaraz J-P, Carde J-P, Bramley PM, Fraser PD, Kuntz M (2007) Fibrillin influence on plastid ultrastructure and pigment content in tomato fruit. Phytochemistry 68 1545-1556... 

Thomson, W.W., Platt, K. Plastid ultrastructure in the barrel cactus, Echinocactus acan-thodes. New Phytol. 72,791-797 (1973)... 

Experiment 5. Observation under transmission electron microscope We compared the TEM ultrastructure of the seed coat and endosperm of control and rue-treated seeds The palisade layer of treated seed appears thicker than in the control (Figs 6A and 7A), while comparison between aleuronic cells of the control and treated cells (Figs. 6B and 7B), reveals that the cells of the control are healthy with some evident organelles such as the nucleus and the rough endoplasmic reticulum and other structures, the plastid, the plasmodesmata, conspicous constrictions, protein bodies and... 

Figure 4 shows a typical ultrastructure of hairy root cells observed under an electron microscope. In the case of photomixotrophic hairy roots, a plastid with a chloroplast-like structure was observed in the light-grown root cells, being associated with thylakoid membranes and grana stacks the particles in the vi-... 

The order Caryophyllales embraces families which have a characteristic ultrastructure of their sieve-element plastids, namely, the P-III subtype (104). In addition, the widespread occurrence of C4 photosynthesis as well as DNA-RNA hybridization data support this taxonomic treatment (23). Within this order, the occurrence of betalains is restricted to nine of the eleven families of the Caryophyllales. The two exceptions, Caryophyllaceae and Molluginaceae, produce anthocyanins instead. There is controversy regarding the phylogenetic importance of this phenomenon (105). It has been suggested that a division of the Caryophyllales into two phylogenetic lines is possible, the betalain-producing Chenopodiineae and the anthocyanin-producing Caryophyllineae (103) (see Scheme 9). The presence of betalains has been an important criterion in the classification of questionable taxa as demonstrated by various examples (13). 

Although all eukaryotic cells have much in common, the ultrastructure of a plant cell differs firom that of the typical mammalian cell in three major ways. First, all living plant cells contain plastids. Second, the plasma membrane of plant cells is shielded by the cellulosic cell wall, preventing lysis in the naturally hypotonic environment but making preparation of cell fractions more difficult. Finally, the nucleus, cytosol, and organelles are pressed against the cell wall by the tonoplast, the membrane of the large, central vacuole that can occupy 80% or more of the cell s volume. 

The 8-h lag period after GA addition is followed by a 16-(or more) h period of rapid a-amylase synthesis (Fig. 7.1 A). More ultrastructural changes are said to occur in the aleurone cells during this time [66]. These include further proliferation of the RER, distention of the RER cisternae, continued reduction in the size of the aleurone grains, decreases in the number of oil bodies, an increase in the number of plastids, and loss of the phytin globoid. 

Figure 1. EM ultrastructure of (a) unadapted, (b) PEG-adapted and (c) PEG-shocked potato cells. CW, cell wall In, infolding of cell wall LD, lipid droplet M, mitochondria NL, nucleus P, pro-plastid S, starch V, vacuole.

Fig. 7. Model for the subcellular localization of reactions of purine synthesis and ureide biogenesis in nodules of ureide-exportlng legumes. The model is based on results of subcellular fractionation and ultrastructural studies. The processes (shown in the hatched boxes) involved in ureide biogenesis (i.e., nitrogen fixation, ammonium assimilation, precursor synthesis, purine synthesis, energy-yielding metabolism, and purine oxidation and catabolism) may occur in more than one subcellular compartment. The location of the enzymes involved in the conversion of IMP to xanthine is not certain. We have proposed that in soybean nodules these reactions [shown in bold-face type with bold arrows] occur in the plastid while in other species such as cowpea these reactions may take place in the ground cytoplasm. In all cases the intermediate exported from the plastid is uncertain. This uncertainty is indicated with the dashed lines and question marks.

Fig. 8. Ultrastructure of a soybean nodule. The electron micrographs presented in this figure were kindly provided by Professors E. Newcomb, M. A. Webb, and their colleagues in the Department of Botany, University of Wisconsin, Madison, Wisconsin. B, Bacteroid P, plastid Ps, peroxisome M, mitochondria. (A) Cross-section of the central infected region of a soybean root nodule containing infected (1) and uninfected (U) cells. (B) Cross-sectional view showing contact of uninfected cells with at least one infected cell. (C) Concentration of peroxisomes and endoplasmic reticulum (ER) in uninfected cells and plastids and mitochondria in infected cells at contact points around intercellular spaces are quite evident as shown in this micrograph. (D) Gold labeling of peroxisomes using anti-uricase antibody appears only in uninfected cells.

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