The distribution and ultrastructure of chloroplasts in leaves differing in photosynthetic carbon metabolism. II. Atriplex rosea and Atriplex hastata (Chenopodiaceae)

1969 ◽  
Vol 47 (6) ◽  
pp. 915-919 ◽  
Author(s):  
W. J. S. Downton ◽  
T. Bisalputra ◽  
E. B. Tregunna

Some aspects of chloroplast development for parenchymatic bundle sheath cells and mesophyll cells of Atriplex rosea leaves are described. The mesophyll chloroplasts begin to degenerate when the bundle sheath chloroplasts have reached a stage of maximum development. These events are related to the changing roles of the two types of chloroplasts in carbon dioxide assimilation. Leaves of Atriplex rosea are similar to those of tropical grasses in leaf anatomy, photosynthetic carbon metabolism, and CO2 compensation value. Atriplex hastata differs from A. rosea in leaf anatomy and is photosynthetically similar to the temperate grasses. There is a lack of parenchymatic sheath development and the chloroplasts which surround the vascular bundle are ultrastructurally identical with those in the rest of the mesophyll.

1969 ◽  
Vol 47 (1) ◽  
pp. 15-21 ◽  
Author(s):  
T. Bisalputra ◽  
W. J. S. Downton ◽  
E. B. Tregunna

The ultrastructure of the chlorenchymatous tissues around the vascular bundles of three different types of grass leaves is described. In the temperate grass leaf, as exemplified by wheat, the inner mestom sheath contains proplastids. Normal chloroplasts are found only within the mesophyll cells. Smaller chloroplasts occur in cells of the ill-defined parenchymatic bundle sheath. This type of leaf has the photosynthetic pathway described by Calvin and a high carbon dioxide compensation value. In the tropical grasses, Sorghum and Aristida, the new photosynthetic pathway proposed by Hatch et al. and low carbon dioxide compensation are correlated with development of the parenchymatic bundle sheath. Cytological evidence indicates that cells of the bundle sheath are much more active than the surrounding mesophyll tissue. The specialized chloroplasts of the bundle sheath cells may be responsible for the physiological and biochemical differences between leaves of tropical and temperate grasses.


Development ◽  
1998 ◽  
Vol 125 (10) ◽  
pp. 1815-1822 ◽  
Author(s):  
E.A. Kinsman ◽  
K.A. Pyke

Bundle sheath cells form a sheath around the entire vascular tissue in Arabidopsis leaves and constitute a distinct leaf cell type, as defined by their elongate morphology, their position adjacent to the vein and by differences in their chloroplast development compared to mesophyll cells. They constitute about 15% of chloroplast-containing cells in the leaf. In order to identify genes which play a role in the differential development of bundle sheath and mesophyll cell chloroplasts, a screen of reticulate leaf mutants of Arabidopsis was used to identify a new class of mutants termed dov (differential development of vascular-associated cells). The dov1 mutant clearly demonstrates a cell-specific difference in chloroplast development. Mutant leaves are highly reticulate with a green vascular pattern. The underlying bundle sheath cells always contain normal chloroplasts, whereas chloroplasts in mesophyll cells are abnormal, reduced in number per cell and seriously perturbed in morphology at the ultrastructural level. This demonstrates that differential chloroplast development occurs between the bundle sheath and mesophyll cells in the Arabidopsis leaf.


1974 ◽  
Vol 52 (9) ◽  
pp. 2017-2021 ◽  
Author(s):  
Nels R. Lersten ◽  
Kathryn A. Carvey

Leaves of ocotillo, a shrub of southwestern North America, lack xeromorphic features. After rain, a few leaves at each node expand and function for a short period, then abscise. This cycle may be repeated several times each year. Palisade layers occur interior to both epidermal surfaces, and the spongy mesophyll is reduced. Venation is camptodromous, with many vein endings. In the distal lamina half, sclerified bundle sheath cells ("veinlet elements") become increasingly common in minor veins and vein endings. Near the leaf tip, adjacent mesophyll cells also become sclerified, to such an extent that some areoles appear filled with these cells ("accessory veinlet elements"). Phloem is conspicuous because it stains intensely and occupies more volume than xylem in most bundles. In minor veins and vein endings, sieve tube members become increasingly more slender than associated phloem cells, and xylem frequently changes its position, becoming parallel with, or even abaxial to, the phloem. Phloem mostly ends before, less commonly with, the xylem.


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