Die Bedeutung der Gerstengranne für die Kornentwicklung II. Anteil der Grannen an der Photosynthese der Ähren

Zusammenfassung Die Photosyntheseintensität von intakten und entgraunten Gerstenähren im Blühstadium wurde gemessen und aus beiden Werten die Photosyntheserate der Grannen ermittelt. Der Anteil der Grannen an der Photosynthesetätigkeit der gesamten Ähre betrug bei der zweizeiligen Sommergerste Haisa über 70%, bei der sechszeiligen Wintergerste Peragis Mittelfrühe fast 80% und bei der weißspelzigen Mutanteeburata etwa 85%. Die entgrannten Ähren voneburata gaben auch im Licht CO₂ ab.

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Summary The photosynthetic rate of flowering barley ears was measured before and after detaching the awns and from both values the photosynthetic rate of the awns calculated. The contribution of awns to the photosynthetic activity of the intact ear was about 70 per cent in Haisa, about 80 per cent in Peragis Mittelfrühe, and in the mutanteburata with white glumes and green awns about 85 per cent. The awnless ears ofeburata showed a CO₂-output in light.

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m ¶rt;u . . , , 70%, - — 80%, eburata — 85%. eburata CO₂ .

     

Effect of Short‐Term Scrotal Hyperthermia on Spermatological Parameters,Testicular Blood Flow and Gonadal Tissue in Dogs

The objective was to assess the effect of a short‐term scrotal hyperthermia in dogs on quantitative and qualitative ejaculate parameters, testicular blood flow and testicular and epididymal histology. After a control period, the scrotum of seven normospermic adult beagle dogs was insulated with a self‐made suspensory for 48 h. Nine weeks later, two animals were castrated, while in five animals, scrotal hyperthermia was repeated. Dogs were castrated either 10 or 40 days thereafter. In each phase of scrotal insulation, average scrotal surface temperature increased by 3.0°C. Semen was collected twice weekly throughout the experiment. Total sperm count did not change after the first hyperthermia, but it slightly decreased after the second (p < 0.05). Profiles of sperm morphology and velocity parameters (CASA) rather indicated subtle physiological variations in sperm quality than effects of a local heat stress. Chromatin stability of ejaculated spermatozoa as indicated by SCSA remained constant throughout the experiment. Perfusion characteristics of the gonads, that is, systolic peak velocity, pulsatility and resistance index at the marginal location of the testicular artery, did not change due to hyperthermia (p > 0.05). Histological examination of excised testes and epididymides for apoptotic (TUNEL and activated caspase‐3) and proliferating cells (Ki‐67 antigen) indicated only marginal effects of scrotal insulation on tissue morphology. In conclusion, a mild short‐term scrotal hyperthermia in dogs does not cause substantial changes in sperm quantity and quality. In contrast to other species, canine testes and epididymides may have a higher competence to compensate such thermal stress.     

A Comparison of SIR-B Synthetic Aperture Radar Data with Ocean Internal Wave Measurements

An image from the Shuttle Imaging Radar-B (SIR-B) synthetic aperture radar (SAR) shows internal wave features in an area south of Long Island, New York Coincident oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected SAR image intensity modulations associated with the internal waves. There is reasonable agreement between the predicted and observed internal wave signatures.     

The genetic basis of singlet oxygen-induced stress responses of Arabidopsis thaliana

Plants under oxidative stress suffer from damages that have been interpreted as unavoidable consequences of injuries inflicted upon plants by toxic levels of reactive oxygen species (ROS). However, this paradigm needs to be modified. Inactivation of a single gene, EXECUTER1, is sufficient to abrogate stress responses of Arabidopsis thaliana caused by the release of singlet oxygen: External conditions under which these stress responses are observed and the amounts of ROS that accumulate in plants exposed to these environmental conditions do not directly cause damages. Instead, seedling lethality and growth inhibition of mature plants result from genetic programs that are activated after the release of singlet oxygen has been perceived by the plant.     

Intrageneric hybrids within the genusFlaveria Juss. (Asteraceae)

Summary The genusFlaveria contains C₃- as well as C₄- and C₃–C₄ intermediate photosynthesis species. This makes it an interesting genus for studies of the evolution of the C₄-pathway of photosynthesis. Hybrids between species offer the possibility for studies of the inheritance of C₄ traits. Four such cross combinations are described with regard to their morphology, leaf anatomy and CO₂ gas exchange properties.

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Intragenerische Hybriden in der GattungFlaveria Juss. (Asteraceae)

Zusammenfassung In der GattungFlaveria kommen C₃-, C₄- und C₃–C₄-intermediäre Arten bezüglich des Photosynthesetyps vor. Das macht die Gattung interessant für Untersuchungen zur Evolution des C₄-Weges der Photosynthese. Arthybriden eröffnen die Möglichkeit zur Untersuchung der Erblichkeit von C₄-Merkmalen. 4 Arthybriden werden in bezug auf Morphologie, Blattanatomie und CO₂-Gaswechsel beschrieben.

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Flaveria Juss. (Asteraceae)

Flaveria , C₃-, C₄- C₃–C₄-. , ¶rt; ¶rt; C₄-. C₄. 4 , CO₂.