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Biomedical subjects

J E Baker

Publications and source records attributed to J E Baker.

120 records · Page 7Linked to original sources
PubMed1970

Changes in Respiration and Cyanide Sensitivity of the Barley Floret during Development and Maturation.

The 6-week period of development and maturation of the barley (Hordeum vulgare L.) floret from anthesis to harvest is characterized by two phases: an early phase of rapid increase in respiration rate and dry weight, and a late phase during which respiration decreased rapidly whereas dry weight remained unchanged. Consumption of O(2) by the embryo changed little during the entire developmental period, whereas O(2) uptake by the endosperm and the lemma and palea decreased significantly during the late phase.Maximal inhibition of O(2) uptake by cyanide in whole florets and floret parts coincided with maximal respiration and growth rates. Differences in sensitivity of embryo and endosperm to cyanide, as the floret matured, appeared to be related to developmental differences between these two tissues. Electron micrographs of embryo and endosperm cells are presented to illustrate some of their ultrastructural features, both at early and late stages of development. Increases in O(2) uptake and cyanide sensitivity of the caryopsis after the lemma and palea were removed suggested that the lemma, palea, and pericarp contributed partly to the increased resistance of the mature floret to cyanide by acting as barriers to gas exchange, thus restricting the movement of both cyanide and oxygen into the caryopsis.

Journal Article↗
PubMed1968

Studies on ultrastructure and purification of isolated plant mitochondria.

Sweetpotato mitochondria, that showed respiratory control, were studied with respect to ultrastructure. If fixed in media containing sucrose at 0.4 M, the cristae were dilated and the matrix was highly condensed. A more orthodox ultrastructural form was observed when the mitochondria were fixed in a medium containing sucrose at 0.25 M, i.e., the matrix was more expanded, the cristae were less dilated, and peripherally, the inner membrane element lay adjacent to the outer membrane element. These results are discussed in terms of a sucrose-accessible space (space between outer and inner membrane elements including intracristal space), and a space relatively inaccessible to sucrose (matrix). Ultrastructural shifts were not observed with change in metabolic steady state of the mitochondria. High resolution electron micrographs showed that the ultrastructure of sweetpotato mitochondria is very similar to that of animal mitochondria.Purity and homogeneity of mitochondrial fractions were followed both by phase-contrast and electron microscopy. Preparations from sweetpotato, using older methods, were relatively homogeneous with respect to particle type and size, whereas avocado preparations contained a high proportion of chloroplasts and cellular debris. A method of purification involving sucrose-density-gradient centrifugation was developed. Purified mitochondria exhibited respiratory control and appeared similar to unpurified mitochondria under the electron microscope.

Journal Article↗