Identification of opal phytoliths bonded to the enamel surface of the teeth of Gigantopithecus blacki indicates that this extinct ape had a varied diet of grasses and fruits. By using the scanning electron microscope at magnifications of 2000-6000x specific opal phytoliths were observed and photographed on the fossilized teeth of an extinct species. Since opal phytoliths represent the inorganic remains of once-living plant cells, their documentation on the teeth of Gigantopithecus introduces a promising technique for the determination of diet in extinct mammalian species which should find numerous applications in the field of paleoanthropology as well as vertebrate paleontology.Since the discovery of extinct species, the determination of diet from fossilized teeth has remained a contentious issue. Early paleontologists often drew dietary conclusions from dental cusp patterns, crown height, and overall shape after detailed comparisons with the teeth of living species. Recent studies have focused on more empirical methodologies such as measurement of enamel thickness (1-3), examination of enamel wear striae (4, 5), and the relationship of cusp size, shape, and angulation to biomechanical stresses encountered during mastication (6). All of these techniques share one central theme: the dietary preferences of extinct species are inferred by comparison and analogy with extant species.An alternative technique based on the identification of opal phytoliths found bonded to the enamel surfaces of the teeth of extinct species allows for identification of the actual plant remains eaten by an animal prior to its death. Thus the vegetative dietary preferences of an extinct species no longer have to be inferred but can be demonstrated directly through the identification of phytoliths, the inorganic remains of plant cells, on the teeth of extinct species.Opal phytoliths are created when hydrated silica dissolved in ground water is absorbed through the roots of a plant and carried throughout its vascular system. This silica may be precipitated in the lumina, cell walls, and intercellular spaces of any plant organ, although aerial structures, including leaves, fruits, and inflorescence bracts, tend to accumulate solid silica more frequently than do subterranean organs (7,8). Recent studies have shown that plant families have a strong tendency either to accumulate or not to accumulate silica, and, contrary to traditional expectations, frequency of phytolith production is very high in dicotyledons and Pteridophytes as well as in monocotyledons (7). A marked constancy in both phytolith production and morphology has been demonstrated for many classes of phytoliths, indicating considerable genetic control over these attributes. Furthermore, it has also been shown that numerous woody and herbaceous plant species produce phytoliths identifiable to the familial and generic levels (7-11).Phytoliths have been shown to have numerous applications in archaeology and paleoecology (7,(9)(10)(11)(12). Baker et al. (13) showed in 1959 t...
Short-term (10 minutes) measurements of plasmalemma NO3-influx ( into roots of intact barley plants were obtained using 13NO3-. In plants grown for 4 days at various NO3-levels (0.1, 0.2, 0.5 millimolar), ,0. was found to be independent of the level of NO3-pretreatment. Similarly, pretreatment with Cl-had no effect upon plasmalemma 13NO3-influx. Plants grown in the complete absence of 13N03-(in CaSO4 solutions) subsequently revealed influx values which were more than 50% lower than for plants grown in NO3-. Based upon the documented effects of NO3-or Cl-pretreatments on net uptake of NO3-, these observations suggest that negative feedback from vacuolar NO3-and/or Cl-acts at the tonoplast but not at the plasmalemma. When included in the influx medium, 0.5 millimolar Cl-was without effect upon 13N03-influx, but N1H4 caused approximately 50% reduction of influx at this concentration.was based upon a form of 'pump and leak' system. Previous studies, particularly those of Jackson and his associates (13,15,16), have established that net NO3-efflux can be considerable under appropriate conditions. Through the use of '3NO3-, it is possible to test the above hypothesis directly and to investigate the effect of NO3-or Claccumulation upon plasmalemma NO3-influx. Using barley plants pretreated for 4 d at various NO3-levels and at a single Cl-level, plasmalemma 13NO3-influx values were found to be independent of pretreatment. While preliminary, the results of these experiments confirm the original conclusions regarding the insensitivity of influx to vacuolar [NO3 1. Likewise, it is evident that 13N03-influx is insensitive to prior loading with Cl-, a condition which has been clearly demonstrated to reduce net 7,19). These results are discussed in the context of current perceptions of the regulation of NO3-uptake in roots.
The timing of crop introductions, particularly of maize (Zea mays), has been of long-standing interest to archaeologists working in various regions of eastern North America. The earliest confirmed macrobotanical evidence for maize in New York is A.D. 1000. We report on the results of accelerator mass spectrometer (AMS) dating, phytolith analysis, and stable carbon isotope analysis of carbonized cooking residues adhering to the interior surface of pottery sherds from three sites in the northern Finger Lakes region of New York. Maize, squash (Cucurbita sp.), wild rice (Zizania aquatica), and sedge (Cyperus sp.) were identified in phytolith assemblages dating to as early as the first half of the calibrated seventh century A.D. The results demonstrate that low δ13C values on cooking residues cannot be used to preclude the possibility that maize was cooked in vessels. Two of the maize-bean-squash crop triad were present in New York at least 350 years earlier than previously documented, and the Northern Flint Corn Complex was present in New York by at least the first half of the seventh century A.D. This research highlights the potential of cooking residues to provide new insights on prehistoric plant-based subsistence.
ABSITRACrAn improved method of counting acostic emissiou (AE) events from water-stressed stems of cedar (Tkutja occideatalis L.) is prented. Am The AE detection technique is used extensively in the engineering sciences to detect the onset of structural failure in metals and other solids under mechanical stress (5). However, it is uncertain what kind of structural failure is being measured in cedar sapwood. As a whole shoot dehydrates in air the tension (= -I',p) on the xylem water columns increases and the xylem cell walls also experience a compressive force because the ambient air is at a higher pressure than the fluid in the xylem conduits. The structural failure events which generate AEs could originate from the water columns breaking (= cavitations) or from breaking of cellulose fibers in the xylem cell walls. It is important to know which is the case in order to test the hypothesis that ultrasonic AEs are reliable indicators of cavitation events.
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