Fig 1
A cross section of a leaf of Potamogeton lucens in the mid-rib region (upper; • 135) and one enlarged sheath cell (lower; x 1350) as seen in the light-microscope after staining with neutral-red, e.w., cell wall; chlor, chloroplast; vae, vacuole.
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Transport is an important feature of the contact between plants and their environment. In many lower plants, the plant body, or the population of cells is predominantly of a single type and this cell type mediates all the exchanges between the plant and its environment. This is partly the reason why certain algal cells (Part A, Chap. 6) and fungal hyphae (Part A, Chap. 7) have become standard systems for study of transport processes (e.g. Chara, Chlorella, Neurospora).
Grown under saline conditions, Suaeda maritima accumulates Na(+) and Cl(-) into its leaves, where individual mesophyll cells behave differently in their compartmentation of these ions. Measurements of ion concentrations within selected subcellular compartments show that freeze-substitution with dry sectioning is a valuable preparative technique for analytical electron microscopy of highly vacuolate plant material. Using this approach, absolute estimates were made of Na(+), K(+) and Cl(-) concentrations in the cytoplasm, cell walls, chloroplasts and vacuoles of leaf mesophyll cells.
The mutual effects of several inorganic elements on their X-ray yields were calculated for a theoretical biological sample. These effects were less than 10% for Ca, K, Cl, S, P, Ka radiations. The influence of changes in thickness and density of the specimen on X-ray yields was also calculated. This influence was very large, especially for specimens of thicknesses which were less than half the mean electron range in the material.RésuméLes effets mutuels de plusiers éléments minéraux sur leur rendement de production de rayons X ont été calculés en théorie pour un échantillon biologique. Ces effets étaient inférieurs à 10% pour des radiations Ka de Ca, K, Cl, S et P. L'influence des variations d'épaisseur et de densité des échantillons fut également calculée. Elle se révèla être considerable dans le cas d'échantillons d'épaisseurs inférieures à la moitié du parcours des électrons dans le matériau en question.ZusammenfassungDie Wechselwirkungen einiger anorganische Elemente auf ihren RÖntgenertrag wurden für eine theoretische biologische Probe berechnet. Für Ca, K, Cl, S und P Ka-Strahlungen war die Wirkung geringer als 10%. Der Einfluβ von Dicken- und Dichtenveränderungen in der Probe auf Röntgenerträge wurde auch berechnet. Dieser war sehr groβ besonders bei Proben, deren Dicke kleiner war als die Durchschnittsdurchlässigkeit von Elektronen in diesem Material.
The effects of NaCl on the carboxylating activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were investigated in the presence of two proline-related analogues found in Tamarix jordanis. N-methyl-L-proline ameliorated the inhibition of the activity of Rubisco by NaCl. Full amelioration was reached at 200 mM of this protectant. Protection by N-methyl-trans-4-hydroxy-L-proline was less effective. Significant differences in the Rubisco protein content from different populations of Tamarix jordanis were observed. Moreover, higher carboxylation rates were obtained for Rubisco preparations from plants that had been grown in saline media. These results are discussed with respect to the adaptation strategies of Tamarix jordanis to saline conditions.
A new technique for preparation of plant material for electron probe microanalysis and microautoradiography is described.
Frozen sections are treated with cold (−20°C) xylene drops and frozen-dried at the same temperature. Such treatment preserves
the cellular details of the sections, and avoids the distortions usually caused by fast freeze-drying. This procedure permits
the precise localization of the elements within different subcellular compartments of plant material.
The effects of putrescine on germination and seedling growth of Atropa belladonna plants under the influence of NaCl were studied. Rate of germination, seedling growth, endogenous putrescine and alkaloids content decreased when seeds were subjected to salt stress. Presoaking seeds in 10−2 mM putrescine and treatment with NaCl reduced the net accumulation of sodium and chloride ions in different organs of the plant. Thus, presoaking seeds in 10−2 mM putrescine can alleviate the adverse effect of NaCl during germination and early seedling growth of A. belladonna and increase alkaloids as well as endogenous putrescine.
