ISSN:
1615-6102
Keywords:
ATPase
;
Acid phosphatase
;
Cytochemistry
;
Phloem loading
;
Plasma membrane
;
Sieve tube
;
Zea leaf phosphatase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary The cytochemical localization of phosphatase activity has been carried out on small and intermediate vascular bundles and contiguous tissues of the leaf ofZea mays L. Similar localization patterns were obtained with the nucleoside triphosphates ATP, CTP, GTP, ITP, and UTP, and with ADP and β-GP. Reaction product (lead deposits) was observed on the plasma membrane of all cell types. It was invariably heavier on the plasma membranes of the bundle-sheath cells, vascular-parenchyma cells, and the thin-walled sieve tubes and their associated companion cells than on those of the mesophyll cells. Within the bundles, the heaviest lead deposits frequently were found on the plasma membranes of the thin-walled sieve tubes and the least amount (often lacking) on those of the thick-walled sieve tubes. Formation of reaction product was suppressed by NaF, vanadate, and molybdate but not by PCMBS (p-chloromercuribenzene sulfonic acid). The results of the substrate-specificity and inhibitor-sensitivity studies indicate that a nonspecific acid phosphatase was probably responsible for the deposition of the reaction product and not the plasma membrane H+-ATPase. These results, in addition to an evaluation of the pertinent literature, lead us to conclude that H+-ATPase activity has yet to be demonstrated unequivocally in association with the plasma membrane of phloem cells with lead precipitation procedures. Nevertheless, the differences in amounts of reaction product generally associated with the plasma membranes of the thick- and thin-walled sieve tubes of the maize leaf indicate that the two types of sieve tube differ from one another physiologically.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01354294
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