Characterization of gonidial zone of Cycas revoluta coralloid roots by means of microelectrodes

Microelectrodes 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

SELF INCOMPATIBILITY MECHANISMS IN THE CROCUS SATIVUS AGGREGATE (IRIDACEAE): A PRELIMINARY INVESTIGATION

Two molecular mechanisms responsible for SI (Self-Incompatibility) in dicotyledons were tested in the C. sativus L. aggregate. RNase and peroxidase activity assays were carried out on crude extract from un-, self- and cross-pollinated styles of C. sativus (male-sterile), C. thomasii Ten. (outfertile) and C. cartwrightianus Herb (out-fertile). Results on RNase activity indicate that in the Crocus species studied the rejection mechanism of SI is not based on stylar RNase. Data on peroxidase activity indicate a relationship between pollen tube presence in the style and stylar peroxidase activity. Stylar peroxidase activity increase is related to pollen tube presence but does not stop tube growth. Compatible and incompatible pollen tubes grow along the style and their discrimination occurs in another region of the gynoecium

Latent virus infections in Crocus sativus and Crocus cartwrightianus

In over two decades, while studying saffron reproductive biology, we frequently found ultrastructural alterations typical of potyvirus infection in stigmas, styles and leaves of Crocus solicits (saffron) and C. cartwrightianus (wild and ornamental species, a putative ancestor of saffron) from different provenance. This suggests that these viruses are widely diffused in cultivated Crocus spp., possibly causing latent infections. The few data found in literature, while highlighting the general lack of attention given by plant virologists to Crocus spp., nevertheless confirm that potyviruses, particularly Bean yellow mosaic virus (BYMV), can cause asymptomatic infections in these host species. The reasons and possible implications of widely distributed potyvirus latent infections in Crocus spp. are reported and discussed, with the aim of increasing general awareness of these viruses, and of encouraging sanitary selection programs focused on saffron, that could improve the quantity and quality of yields of the most expensive spice commodity grown

CYTOPLASMIC RESERVES IN GENERATIVE AND VEGETATIVE CELLS OF HERMODACTYLUS TUBEROSUS MILL.: CYTOCHEMISTRY, ESI AND EELS ANALYSES

This 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