The Correlated Appearance of Prolamellar Bodies, Protochlorophyll(ide) Species, and the Shibata Shift during Development of Bean Etioplasts in the Dark

The structure and physiology of the etioplast was investigated in developing primary leaves of 3- to 9-day-old dark-grown bean (Phaseolus vulgaris L. var. Red Kidney) seedlings. Increase in total protochlorophyll(ide) content followed that of leaf fresh weight. In 3- to 4-day-old bean leaves more than 50% of the protochlorophyll(ide) is in the form of protochlorophyll(ide) 628, which is nontransformable by light. Most of the transformable pigment is protochlorophyll(ide) 635, with smaller amounts of protochlorophyll(ide) 650. During leaf development from the 3rd to the 7th day phototransformable protochlorophyll(ide) with an absorbance maximum at 650 nm accumulates faster than nontransformable protochlorophyll(ide) or protochlorophyll(ide) 635. This increase in protochlorophyll(ide) 650 is correlated with the formation and enlargement of prolamellar bodies.The transformable protochlorophyll(ide) is converted by light directly to chlorophyll(ide) 672 in young leaves which do not yet have prolamellar bodies, and chlorophyll(ide) 672 may arise largely from the protochlorophyll(ide) 635. In older leaves the protochlorophyll(ide), largely protochlorophyll(ide) 650, is converted to chlorophyll(ide) 683, and a Shibata shift results in a change in the wavelength of absorption to 672 nm. The increase in protochlorophyll(ide) 650, the formation of prolamellar bodies, and the presence of the Shibata shift appear to be closely correlated. A model is briefly presented to provide a unified interpretation of these findings, including certain similarities between dark-grown Euglena cells and 3- to 4-day-old etiolated bean leaves.

The effect of water stress on mitochondria of root cells: a biochemical and cytochemical study

Water loss from root cells of Zea mays induced by exposure to severe water stress, caused a reduction in the respiratory rate (O(2) consumption) and at the same time an increase in activity of the mitochondrial cytochrome oxidase (histochemical oxidation of diaminobenzidine). The connections between these changes and the changes in the fine structure of the mitochondria occuring in the stressed roots are discussed.

Changes in Fine Structure of Root Cells from Maize Seedlings Exposed to Water Stress

As previously reported (Nir et al. 1969) changes in the ultrastructure of meristematic cells were induced by exposure of detached maize root tips to water stress. The question remained whether similar fine structure changes would be induced if instead of isolated root tips, the whole seedlings were exposed to water stress. Since knowledge of the behaviour of intact seedlings is important for the understanding of drought physiology, we investigated the changes which occur in the fine structure of root cells when whole seedlings are exposed to drought.

Effeot of Moisture Stress on Submicrosoopic Struoture of Maize Roots

The effect of dehydration on root behaviour and its submicroscopic structure was studied. Root segments were dehydrated above sodium chloride solutions of various concentrations and the degree of dehydration was expressed as percentage loss of weight. Loss of more than 70% of initial weight proved lethal. On loss of 60-70% some of the roots preserved their ability to resume growth on rehydration.

Studies of Fine Structural and Biochemical Changes in Cotyledons of Germinating Soybeans

Ultrastructural changes have been observed in the soybean cotyledon during early germination and subsequent seedling growth. Concurrently measurements were made of fresh and dry weight, chlorophyll and protein content, and porphyrin and protein synthesis.