Biomedical subjects

C E Hartt

Publications and source records attributed to C E Hartt.

16 recordsLinked to original sources

PubMed1972

Translocation of carbon-14 in sugarcane plants supplied with or deprived of phosphorus.

Translocation of radioactive carbon from the fed part of a blade to the rest of the plant was impaired by a deficiency in phosphorus only when the level of phosphorus was low enough to decrease growth.Phosphorus deficiency decreased the percentage of inorganic phosphorus more than that of organic phosphorus, indicating little effect of phosphorus deficiency upon phosphorylation.Thus phosphorus deficiency did not reduce phosphorylation enough to affect translocation. Evidence for the involvement of phosphorylation in translocation obtained from studies with potassium deficiency, light intensity and quality, 3-(p-chlorophenyl)-1, 1-dimethylurea and 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, and carbon dioxide suggests that noncyclic photosynthetic phosphorylation provides the energy for phototranslocation.

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PubMed1970

Effect of Potassium Deficiency upon Translocation of C in Detached Blades of Sugarcane.

The translocation of radioactive photosynthate was studied in blades detached from plants which had been grown in nutrient solution with and without potassium. Basipetal translocation decreased in the blades of plants deprived of potassium, even when deficiency symptoms were not visible. In such slightly potassium-deficient leaves, translocation was decreased in the light but not in the dark. More severe potassium deficiency decreased translocation both in darkness and in light. Potassium deficiency decreased translocation at light intensities giving no difference in rate of photosynthesis between plus and minus potassium leaves and even at light intensities at which there was no net fixation of carbon dioxide. At all levels of deficiency, the relative decrease in translocation was greater than the relative decrease in photosynthesis. Translocation was affected at potassium deficiency levels which had no effect upon photosynthesis.Potassium deficiency decreased translocation relatively more than it decreased moisture content. There was a much better correlation between the decrease in potassium and translocation than between the decrease in moisture and translocation.An experiment with radioactive phosphorus indicated an upset in phosphorylation in the stems of potassium-deficient plants.

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PubMed1970

Effect of Nitrogen Deficiency upon Translocation of C in Sugarcane.

Withholding nitrogen decreased the percentages of nitrogen and chlorophyll in the blades; reduced the total fixation of radioactive carbon dioxide at 15, 37, and 178 seconds; and changed the relative composition of fixation products. Translocation of radioactive photosynthate from the fed part down the attached blade and into the stalk was less in the plants deprived of nitrogen than in the control plants supplied with nitrogen. Both the percentage of total activity translocated and the velocity of transport were decreased by nitrogen deficiency. During a translocation period of 90 minutes the minus nitrogen blade retained more (14)C-sucrose than the control in the fed part and the blade below the fed part, but it sent less (14)C-sucrose to the sheath of the fed leaf. Thus translocation decreased with nitrogen deficiency not for lack of sucrose but for some other reason. Although withholding nitrogen decreased translocation of labeled carbon in and from attached blades, there was no effect upon transport in detached blades. The effect of nitrogen deficiency upon translocation may be indirect and secondary to the effect upon growth of the plant as a whole.

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PubMed1969

Effect of potassium deficiency upon translocation of C in attached blades and entire plants of sugarcane.

A deficiency in potassium decreased the translocation of labeled photosynthate from the leaf to the rest of the plant. Translocation was inhibited in blades which exhibited no visible symptoms of potassium deficiency and in which no decrease in photosynthesis was detected. In more severe deficiency both the rate of photosynthesis and the conversion of intermediates to end products decreased. The rate of respiration in deficient blades increased. The decrease in translocation caused by potassium deficiency is considered to be a primary effect and not secondary to the development of the well-known symptoms of potassium deficiency.

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PubMed1967

Translocation of C in the sugarcane plant during the day and night.

The time-course of translocation of (14)C from the blades of the sugarcane plant was investigated by analysis and radioactive counting of successive samples punched from a single blade. In 1 experiment, the time-course was studied by determining the specific activity of the carbon dioxide respired by the roots.The rate of translocation, expressed as percentage, was highest immediately after the application of the radioactive carbon dioxide. Morning-made photosynthate translocated a higher percentage during the morning than during the afternoon in 90-minute periods in the light. Afternoon-made photosynthate translocated as well or better than morning-made photosynthate for the first hour in the light.The leaf-disk data and the specific activity of the carbon dioxide respired by the roots corresponded by showing lower rates of translocation by night than by day for several successive days. Also, the translocation of (12)C sucrose was slower at night.The (14)C sucrose translocated by day was made primarily by photosynthesis; the sucrose translocated by night was made primarily by the conversion of other labeled compounds, e.g. organic acids, organic phosphates, and insoluble residue.The radioactive constituent of the residue, which was converted to sucrose, was tentatively identified as a glucose-xylose-glucuronic acid hemicellulose, with most or all of the (14)C in the glucose moiety.Translocation of sucrose may be triggered by different mechanisms during the night than the day. The conversion of insoluble residue to sucrose by increasing the osmotic potential at the source would favor a pressure-flow mechanism for nocturnal translocation; whereas translocation by day is thought to be a process of phototranslocation, a photoactivation of the translocation mechanism.

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PubMed1967

Effect of Moisture Supply upon Translocation and Storage of C in Sugarcane.

Low moisture supply, controlled by 3 methods (adding NaCl to a complete nutrient solution, allowing a cut stalk to wilt, or withholding irrigation in the field), decreased the velocity and percentage rate of translocation of (14)C-photosynthate. The surplus sucrose not used in growth moved more slowly in the phloem and was stored in the stalk.Low moisture supply depressed translocation of (14)C-photosynthate more severely than it curtailed formation of (14)C-photosynthate in the same leaf: therefore, the effect of moisture supply upon translocation was primary.Low moisture supply retarded profile development in the stem, and a loss in moisture gradient was associated with a steepened slope of the profile. These results indicate a flow mechanism of translocation rather than diffusion.Results reported now and previously point to the operation of a slow pressure-flow mechanism particularly during the night but also during the day; superimposed upon this general mass transport is the more rapid process of phototranslocation which is independent of sugar gradients and which can cause the accumulation of sucrose at the storage-sink.During ripening, storage of sucrose in the stalk may be increased by withholding water because less sucrose is hydrolyzed in transit, less is used in growth, and the slowly moving sucrose has more time for transfer from the phloem to the storage parenchyma.

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PubMed1966

Translocation in colored light.

The translocation of (14)C-photosynthate in detached blades of sugarcane was studied under illumination from red, green, blue, and cool-white fluorescent lamps; under far-red illumination from the sun, and from incandescent lamps; and in total darkness.The percentage of basipetal translocation and the accumulation against the concentration gradient were stimulated by light from the red or blue lamps more than by green or cool-white fluorescent illumination.Basipetal translocation took place equally well in red light lacking blue irradiation and in blue light. Since the action spectrum for light-induced change in viscosity is a typical blue-type spectrum, the effect of light upon translocation is not due merely to changes in the physicochemical properties of protoplasm.Basipetal translocation took place in red light lacking blue irradiation better than in cool-white fluorescent light, which may suggest a red stimulation of translocation.Illumination in the far-red region of the spectrum did not support basipetal translocation but acted like total darkness.Because of the wide emission characteristics of the fluorescent lamps employed, it is impossible to decide whether a chlorophyll-like system or some other pigment is involved in the light stimulation of phototranslocation.Whatever the activating wavelength and whatever the pigment system involved, these results show that the phototranslocation of sucrose in the phloem is influenced by the quality of illumination.

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PubMed1965