1,721,018 research outputs found
Characterization of gonidial zone of Cycas revoluta coralloid roots by means of microelectrodes
No full textMicroelectrodes were used for measurements of oxygen, ammonium, potassium and calcium concentrations within gonidial zones of Cycas revoluta coralloid roots. Gonidial zone segments contained an oxygen pressure of 85% with respect to its concentration in the atmosphere. Dissolved ammonium was detected in concentrations between × 10−3 M and 4 × 10−3 M. The highest ammonium concentration was in intermedial segments and it could cause the decrease of nitrogenase activity. Potassium concentration was in the range 5.5–9 × 10−3 M; calcium concentration was 10−6 M in apical and subapical segments, it reached 1–2 × 10−5 M in the intermedial and basal segments. Calcium concentrations could affect heterocyst differentiation, nitrogen fixation and mucilage composition of coralloid roots
Ultrastructure of chromoplasts and other plastids in Crocus sativus L. (Iridaceae)
No full textSaffron (Crocus sativus L. Iridaceae) chromoplasts and other plastids were studied by electron microscope to determine their structure, origin and pigment localization. Plastids from pistils of floral buds and flowers at anthesis, dried and decoloured stigmas, and green and senescent leaves were examined. Results indicated that mature saffron chromoplasts occur in the red parts of stigmas and have a reticulo-tubular structure. They contain a reticulum of tubules and plastoglobules. Tubules formed dilated vesicles mainly while plastoglobules appeared numerous and scattered on the whole chromoplast. Chromoplasts appeared in red stigma of very young floral buds. They originated from amyloplasts, the only plastids occurring in the colourless basal portion of style, as well as in the parenchyma of ovary and corm. Transition forms of plastid as amylo-chromoplast, occur in the yellow parts of stigma and style. Senescent leaves did not show plastids with structure similar to the chromoplast of red stigma. Red pigmented and scented stigmas might cooperate in saffron reproduction by attracting pollinator
CYTOPLASMIC RESERVES IN GENERATIVE AND VEGETATIVE CELLS OF HERMODACTYLUS TUBEROSUS MILL.: CYTOCHEMISTRY, ESI AND EELS ANALYSES
No full textThis study uses cytochemical tests, electron spectroscopic imaging and electron energy loss spectroscopy techniques
to identify and localize the reserves inside the generative cell of Hermodactylus tuberosus pollen. Cytochemical probes
applied to sections observed by light and transmission electron microscopy indicated that the generative cell contains
large osmiophilic bodies probably made of phytic acid rich in P and Ca. The significance of the rich granulations in
generative cells of Hermodactylus pollen is discussed in relation to floral biology and environmental conditions. In
comparison, the vegetative cytoplasm contains (a) lipid droplets formed by unsaturated lipids and related to vacuoles,
(b) lipid bodies with larger dimensions, irregular in shape and very rich in Ca, (c) bodies stained in polysaccharide
tests as well as lipid probes tentatively identified as glycolipid granulations, and (d) small granules very rich in P and
Ca interpreted as phytin granules
Sub-cellular localization of calcium in Azolla-Anabaena symbiosis by chlotetracycline, ESI and EELS
No full textThe subcellular localization of calcium in cells of symbiotic partners located within leaf cavities of Azolla was investigated by using chlorotetracycline, ESI and EELS analysis. Loosely membrane-bound calcium was evidenced by using CTC or EGTA and CTC, in cytoplasmic regions of Azolla hair cells and in cytoplasm of the cyanobiont. Tightly membrane-bound calcium revealed by CTC, and ESI and EELS analysis, was observed in cyanophycin granules and carboxysomes of the cyanobiont. A third calcium type, revealed by ESI and EELS analysis, was localized at the level of cell walls of simple and branched Azolla hairs, in the envelope of heterocysts, and in the cell walls of the cyanobiont
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