Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA‐DAPI complex in nuclei released from different fresh and formaldehyde‐fixed pea (Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue.
The ability of ascorbic acid to induce cell proliferation of non‐cycling cells was investigated in quiescent embryo root of Pisum sativum L. cv. Lincoln, as well as in the active plantlet root meristem, where a minor portion of the cells is non‐proliferating. Quiescent embryo cells speeded up the G0–G1 transition during germination in the presence of ascorbic acid. In addition, proliferating cells present in the root tip of 3‐day‐old plantlets, arrested at the G1/S boundary by hydroxyurea, resumed the cycle earlier than the control, when treated with ascorbic acid. In contrast, ascorbic acid was unable to induce the proliferation of non‐cycling cells present in the active meristem. Therefore, these data suggest that the ability of ascorbic acid lo induce cell proliferation depends on the physiological status of the cell. In particular the data indicate that ascorbic acid is involved in cell proliferation as a factor necessary to enable already competent cells to progress through the cell cycle phases, but not as a factor able to induce non‐competent cells to overcome proliferation arrest.
SUMMARYMicroHuorimetric and flow cytometric analyses were used in nuclei of cortical cells of roots in the endomycorrhizal system Allium porrum L. + a Glomus sp., strain E., (from Rothamsted Station), in an attempt to explain nuclear hypertrophy. No variation of DNA content in comparison with the controls was observed in mycorrhizal roots. An increase of fluorescence (about 25 "o) vvas observed in mycorrhizal root nuclei stained with an undersaturating concentration of DAPI. This can be explained by a greater accessibility of DNA to Huorochromes owing to a lower degree of chromatin condensation, as confirmed by ultrastructural data.Our results suggest a possible explanation of nuclear hypertrophy and, further, show that variations of chromatin condensation can occur in mature plant cell nuclei, even though this, in differentiated plant cells, is generally considered to be independent of the cellular functions.
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