Effect of Light on the Volume and Ion Relations of Chloroplasts in Detached Leaves of Elodea Densa

Fillippis, LF De; Pallaghy, CK

doi:10.1071/bi9731251

Cited by 17 publications

(10 citation statements)

References 18 publications

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“…The apparent absence of chloride in such cells in dark samples suggests that this ion was either leached out of these cells or that it was absorbed from vascular cells by the mesophyll and bundle sheath cells via a dark-stimulated transport mechanism. The latter suggestion would be consistent with the higher Cl : K ratios in the tissue of dark-treated samples, and the fact that dark-induced swelling of chloroplasts in Elodea densa causes a marked increase in their chloride content (De Filippis and Pallaghy 1973). Large xylem vessels appeared to be empty (Fig.…”

Section: (B) Distribution Of Ions In Leaf Sectionssupporting

confidence: 72%

“…This situation was used to advantage by embedding freezesubstituted leaf sections in Spurr's medium and comparing the chlorine X-ray emission (by spot analysis) of an area external to the tissue with that for potassium within the tissue in the same section, thus avoiding the necessity to measure section thicknesses. Using this technique and making the assumption that the X-ray detector is equally sensitive to potassium and chlorine (De Filippis and Pallaghy 1973), the following results were obtained for a leaf section (2 by O' 5 mm) floated on distilled water for 2 hr in darkness:…”

Section: (E) Calibration Of X-ray Detectormentioning

confidence: 99%

“…It is known that bundle sheath chloroplasts are deficient in photosystem II (Polya and Osmond 1972). Other explanations are also possible-there is evidence suggesting that during light-induced shrinkage of chloroplasts in leaves of Elodea, the concentration of ions in the chloroplasts may rise even though there is a net efflux of ions from chloroplasts (De Filippis and Pallaghy 1973). If we assume that light induces a similar net efflux of ions from both bundle sheath and mesophyll chloroplasts, we might expect the concentration of ions to decrease in mesophyll chloroplasts on the basis of their small reduction in volume upon illumination.…”

Section: (D) Differences In Ion Relations Between Bundle Sheath and Mmentioning

confidence: 99%

“…The relative count rates for potassium and chloride were estimated from the corresponding peak heights in the X-ray spectrum after subtraction of background as judged by eye. De Filippis and Pallaghy (1973) reported that the calibration curves for chloride and potassium were almost linear for X-ray spectra analysed on the basis of peak heights. The range of count rates observed for bundle sheath chloroplasts in the light ranged from 800 to 1300 counts/400 sand depended on section thickness.…”

Section: (B) Electron Probe Microanalysismentioning

confidence: 99%

“…All handling of the sample must be carried out under the most stringent anhydrous conditions (using activated molecular sieve~Union Carbide, type 3A PLTS) right up to the point of introduction of the sample into the vacuum chamber of the scanning electron microscope. Fisher (1972), Fisher andHousley (1972), andPallaghy (1973) have shown that migration of water-soluble substances will occur if the samples are not maintained in an anhydrous state for each step of the preparation procedure. The molecular sieve used in the present study was always activated by heating in a Pyrex tube, under vacuum, over a bunsen flame.…”

Section: (B) Preparation A/tissue (I) Generalmentioning

confidence: 99%

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Electron Probe Microanalysis of Potassium and Chloride in Freeze-Substituted Leaf Sections of Zea Mays

Ck¹

1973

Aust. Jnl. Of Bio. Sci.

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Small sections of leaves were floated on distilled water under either light or dark conditions, and were freeze-substituted in a 1 % solution of osmium tetroxide in acetone at -78°C followed by embedding in an epoxy resin. Approximately I-11m-thick sections were cut using a dry diamond knife and examined by scanning transmission electron microscopy. The relative concentrations of potassium and chloride in subcellular compartments were determined using an energy dispersive X-ray analyser. The concentration of sodium in the leaf (1·7 m-equivjkg of wet tissue) was too low to be detected by this method. The spatial resolution of this technique was sufficient to distinguish between concentrations in the chloroplasts, cytoplasm, vacuole, and nuclei. The concentration of chloride in stomata and some other epidermal cells was very much higher than in either mesophyll or bundle sheath cells. The potassium concentration in some vascular cells was at least two-to threefold higher than that in mesophyll or bundle sheath cells. The Cl : K ratio in mesophyll and bundle sheath cells resembled that in the solution (0 ·10) used for growing the plants. The concentration of chloride in the "free" cytoplasm of mesophyll cells was always very low. Significant differences were found in the "ion" relations of mesophyll and bundle sheath cells. Whereas the ratio of potassium concentration between the vacuole and chloroplasts of mesophyll cells was high (1 ·19) in the light and low (0·65) in the dark, the opposite was true for bundle sheath cells-O· 65 and 0·86 respectively. The ratio of potassium concentration between the vacuo les of mesophyll and those of bundle sheath cells was 1 ·48 in the light, but only 0·76 in the dark. These concentration gradients are discussed in relation to a possible transfer of organic acid salts of potassium between these two cell types.

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Section: (B) Distribution Of Ions In Leaf Sectionssupporting

confidence: 72%

Section: (E) Calibration Of X-ray Detectormentioning

confidence: 99%