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K Esau

Publications and source records attributed to K Esau.

At least 19 recordsLinked to original sources
PubMed1983

Nuclear crystalloids in sieve elements of Boraginaceae: a protein digestion study.

Nuclear crystalloids have been found in sieve elements of several Boraginaceae. Nuclei of differentiating sieve elements of Echium and other genera except Amsinckia contain one or more crystalloids composed of thin rods densely packed in parallel arrangement. After the nuclei disintegrate in the maturing sieve element the crystalloids are released into the cell lumen where they persist intact. In Amsinckia the crystalloid consists of two components: a dense component, similar to the crystalloid in the other genera and a loosely arranged paracrystalline component. The proteinaceous nature of the nuclear crystalloids and their possible similarity to P-protein was investigated by enzyme digestion techniques. Three proteolytic enzymes were employed in this study: protease, pepsin and trypsin. Successful digestion of the dense crystalloid in both Echium and Amsinckia was obtained with each enzyme tested. P-protein plugging the sieve plate pores was also digested. The loose component in Amsinckia and the aggregated and dispersed P-protein were not affected by the enzyme digestion procedures. These results seemed to indicate that the density or compactness of the proteinaceous inclusions may play a role in the differential response.

Cell Nucleus↗
PubMed1979

A crystalline inclusion in sieve element nuclei of Amsinckia. I. The inclusion in differentiating cells.

The presence of usually single, elongated, compound crystalloids in nuclei of sieve elements is an outstanding characteristic of the phloem of Amsinckia douglasiana A. DC. (Boraginaceae). The crystalloid consists of two components forming alternating panels, or blocks, that extend through the entire length of the crystalloid and radiate from the centre where one of the components predominates. Three to seven panels for each component were recorded. One component consists of 4-sided tubules closely packed in highly ordered aggregates, the other of wider 6-sided tubules rather loosely arranged in paracrystalline aggregates. The crystalloid arises at the beginning of sieve element differentiation. Aggregates of 4-sided tubules appear first. In plants infected with the curly top virus, the crystalloids do not differ from those in non-infected controls in structure and conformation. But because the phloem in infected plants is hyperplastic, with most of the cells differentiating as sieve elements, the crystalloids are far more abundant in diseased than in healthy plants.

Cell Differentiation↗
PubMed1979

A crystalline inclusion in sieve element nuclei of Amsinckia. II. The inclusion in maturing cells.

The compounds crystalloids formed in sieve element nuclei of Amsinckia douglasiana A. DC. (Boraginaceae) during differentiation of the cell become disaggregated during the nuclear breakdown characteristic of a maturing sieve element. The phenomenon occurs in both healthy and virus-infected plants. The crystalloid component termed cy, which is loosely aggregated, separates from the densely aggregated component termed cx and disperses. The cx component may become fragmented, or broken into large pieces, or remain intact after the cell matures. After their release from the nucleus both crystalloid components become spatially associated with the dispersed P-protein originating in the cytoplasm, but remain distinguishable from it. The component tubules of P-protein are hexagonal in transections and are somewhat wider than the 6-sided cy tubules. The cx tubules are much narrower than the P-protein or the cy tubules and have square transections. Both the P-protein and the products of disintegrated crystalloids accumulate at sieve plates in sieve elements subjected to sudden release of hydrostatic pressure by cutting the phloem. The question of categorizing the tubular components of the nuclear crystalloid of a sieve element with reference to the concept of P-protein is discussed.

Cell Division↗
PubMed1975

An ultrastructural study of acid phosphatase localization in cells of Phaseolus vulgaris phloem by the use of the azo dye method.

The localization of acid phosphatase was studied in the sieve elements and companion cells in the phloem tissue of the bean, Phaseolus vulgaris L. The various organelles in the two kinds of cell showed fine granules of the azo dye as the final reaction product. The aggregated smooth endoplasmic reticulum displayed the dye particularly consistently. The dye was also present in the plasmodesmata and in the contents of the sieve plate pores. The reaction product was conspicuous in the cell walls and tended to be concentrated in the middle lamella and in the nacreous wall layer of the differentiating sieve elements.

Acid Phosphatase↗
PubMed1975

An ultrastructural study of acid phosphatase localization in Phaseolus vulgaris xylem by the use of an azo-dye method.

The localization of acid phosphatase during xylem development has been examined in the bean, Phaseolus vulgaris. The azo dye, the final reaction product, is initially prominent in the dictyosomes, vesicles apparently participating in secondary wall formation, and in the middle lamella of the young vessel element. Final reaction particles are also present in mitochondria, chloroplasts, and certain vacuoles and are sparsely scattered in the cytoplasm. At a later stage of vessel differentiation, the azo dye is concentrated in the disintegrating cytoplasm and along the fibrils of the partially hydrolysed primary wall and middle lamella. In the mature vessel element, the azo dye is still present along the disintegrated primary wall at the side of the vessel and covers the secondary wall. In the parenchyma cell adjacent to the vessel element, acid phosphatase localization is found in the dictyosomes, endoplasmic reticulum, mitochondria, small vacuoles, and the middle lamella. The controls from all stages of vessel element development were free of azo dye particles. The concentration of acid phosphatase along the secondary walls of the mature vessels and in the middle lamella between other cells indicates that this enzyme has other functions besides autolysis of the cytoplasm and primary cell wall. Acid phosphatase may participate in the formation of the secondary wall and may also have a role in the secretion and transport of sugars.

Acid Phosphatase↗