Pennsylvanian shark-cephalopod predation: a case study

A well-preserved portion of a body chamber of a coiled nautiloid (taxon uncertain) from the Kendrick Shale (Lower Pennsylvanian) of Floyd County, Kentucky, U.S.A., exhibits three comparatively large, nearly circular punctures and a circular indentation in the shell. These punctures are interpreted as representing an attack on the nautiloid by a cladodontid shark, most likely by the large symmoriid shark, Symmorium reniforme. We conclude that the punctures in the nautiloid body chamber were inflicted by three teeth in a single tooth file in the lower jaw of a specimen of 5. reniforme that was approximately 2.5 meters long. This nautiloid specimen is the first Paleozoic record of a chondrichthyan-cephalopod/ predator-prey relationship. We suggest, however, that this relationship was perhaps a common one and that other examples probably exist in collections of late Paleozoic ccphalopods. ?Paleozoic, Pennsylvanian, Symmorium reniforme, cephalopod. predation.     

Separate Oscillations of the Electrogenic Pump and of a K+ -Channel in Nitella as Revealed by Simultaneous Measurement of Membrane Potential and of Resistance

In Nitella oscillations of membrane potential with periods ofabout 15 min and of about 1 h can be observed. The comparisonof the related changes in resistance and in potential showsthat the 1-h oscillation controls a carrier-type transporter,probably an electrogenic pump with a stoichiometry of 1 H⁺/1ATP. The control loop related to the 1-h oscillation can bestimulated by internal pH as changed by butyrate or procaine.IV-curve studies show that the 15-min oscillation modulatesthe conductivity of a K⁺ -channel. No way has been found toinfluence the spontaneously occurring 15-min oscillation whichprobably is generated in the chioroplasts. The oscillationsseem to provide a means of exerting a selective influence onone transporter. Correspondence to: Institut für Angewandte Physik, NeueUniversität, Haus N61A, D-2300 Kiel, F.R.G. Key words: H⁺-pump, IV-curves, Nitella, oscillations, pH-regulation, potassium channel, stoichiometry     

14C-Studies on Apple Trees. VII. The Early Seasonal Growth in Leaves, Flowers and Shoots as Dependent upon Current Photosynthates and Existing Reserves

The young leaves' consumption proper of photosynthates and their contribution to the growth of flowers, fruits and shoots by exposing spurs and shoots to ¹⁴CO₂ at the earliest stages of the growth period in apple trees (Malus X domestica) were studied. By a parallel determination of the growth intensity in various organs an attempt is made to evaluate their relative dependence on current photosynthates and on reserves from inside the tree. The proper fixation of ¹⁴C by growth in the exposed leaves is high in the earliest phases of growth. The fixation of ¹⁴C is considerable in the flowers, including the petals, immediately prior to flowering, in intensely growing fruits, and in the woody parts of the current year's shoots, when the main part of the terminal growth has been completed. Under conditions of high intensity of growth in an organ, the total fixation by growth in the parts studied may amount to as much as 80–90% of the ¹⁴C absorbed. Only in the very earliest phases of development does the growth of flowers and shoots appear to be based to a greater extent on materials supplied from reserves than from current photosynthesis. Quantitatively the greater part by far of the total new growth in fruits and shoots appears to be based on materials from current photosynthesis.     

Histological Changes of the Peanut (Arachis hypogaea) Gynophore and Fruit Surface During Development, and their Potential Significance for Nutrient Uptake

Histological changes in gynophores and fruits of Arachis hypogaeaL.cv. White Spanish were examined, utilizing scanning electronmicroscopy as well as light microscopy. The epidermis of theabove ground parts of gynophores is characterized by the presenceof stomata, lenticels and multicellular trichomes. Below groundportions of the same plant organ exhibit unicellular root-hair-likestructures. These protuberances of the epidermal cells can reacha very high density and length (up to 0.75mm) . Identical structurescan be found on the developing pod and are most prominent atthe reproductive stages R5-R6. In later developmental stagesthe hairs degenerate and the presence of large lenticels becomesthe obvious external feature of the pod. It is suggested thatthe substantial increase in surface area due to the hairs maywell be an anatomical adaptation for nutrient and water uptake. Arachis hypogaea, peanut fruit development, nutrient uptake