Stomatal responses to CO2 during a diel Crassulacean acid metabolism cycle in Kalanchoe daigremontiana and Kalanchoe pinnata

To investigate the diurnal variation of stomatal sensitivity to CO₂, stomatal response to a 30 min pulse of low CO₂ was measured four times during a 24 h time-course in two Crassulacean acid metabolism (CAM) species Kalanchoe daigremontiana and Kalanchoe pinnata , which vary in the degree of succulence, and hence, expression and commitment to CAM. In both species, stomata opened in response to a reduction in p CO₂ in the dark and in the latter half of the light period, and thus in CAM species, chloroplast photosynthesis is not required for the stomatal response to low p CO₂. Stomata did not respond to a decreased p CO₂ in K. daigremontiana in the light when stomata were closed, even when the supply of internal CO₂ was experimentally reduced. We conclude that stomatal closure during phase III is not solely mediated by high internal p CO₂, and suggest that in CAM species the diurnal variability in the responsiveness of stomata to p CO₂ could be explained by hypothesizing the existence of a single CO₂ sensor which interacts with other signalling pathways. When not perturbed by low p CO₂, CO₂ assimilation rate and stomatal conductance were correlated both in the light and in the dark in both species.     

Toward a plant-based proxy for the isotope ratio of atmospheric water vapor

Atmospheric water vapor is a major component of the global hydrological cycle, but the isotopic balance of vapor is largely unknown. Here, using models and observations, we show that the leaf water δ¹⁸O in the tropical Crassulacean acid metabolism (CAM) epiphyte Tillandsia usneoides is controlled by the δ¹⁸O of atmospheric water vapor in a predictable manner, irrespective of precipitation inputs. By taking the leaf‐water‐atmospheric signature as recorded in plant organic material, we have reconstructed the atmospheric water vapor δ¹⁸O signature for Miami, FL, USA between 1878 and 2005 using contemporary and herbarium specimens. T. usneoides ranges from Virginia, USA southwards through the tropics to Argentina, and the CAM epiphytic lifeform is widespread in other species. Therefore, there is significant potential for using epiphytes to reconstruct the isotope ratio of atmospheric water (both δ¹⁸O and δD) for spatial scales that span over 60° of latitude and temporal scales that cover the last century of global temperature increase.     

The Upper Carboniferous Hamilton Fossil-Lagerstätte in Kansas: a valley-fill, tidally influenced deposit

A diverse assemblage of unusually well-preserved marine, euryhaline, freshwater, and terrestrial fossils (invertebrates, vertebrates, and plants) occurs within an Upper Carboniferous (Stephanian) Konservat Fossil-Lagerstätte near Hamilton, Kansas, USA. The Lagerstätte occurs within a paleovalley that was incised into the surrounding Carboniferous cyclothemic sequence during a time of low sea level, and was then filled-in during a subsequent transgression. The stratigraphically lowest and most voluminous facies within the valley is a cross-bedded, polymictic limestone conglomerate that contains caliche clasts and charcoal fragments as well as some normal-marine fossils apparently in situ. The origin of the conglomerate is enigmatic, but it was probably deposited by a migrating tidal channel. Overlying and interbedded with the conglomerate is an ostracode wackestone that contains plants (primarily seed ferns and ferns), eurypterids, shrimp, brachiopods, bivalves, and rare fish. The ostracode wackestone was deposited in a low-energy, marginal-marine environment. A thin sequence (<1 m thick) of interbedded laminated limestone and mudstone overlies the conglomerate in a small area. This facies contains a well-preserved mixed assemblage of terrestrial (conifers, insects, myriapods, reptile), freshwater (ostracodes), aquatic (amphibians, reptile), brackish or euryhaline (ostracodes, eurypterids, spirorbids, fish), and marine (brachiopods, echinoderms) fossils. Many of the vertebrates are articulated and show no evidence of preburial decay, scavenging, or predation. A few vertebrates exhibit signs of flotation. Most articulated vertebrate specimens exhibit soft-tissue preservation in the form of dark-brown to black early-diagenetic microbialite body outlines (‘skin preservation’) containing fossil bacteria. Rhythmic patterns of lamination thickness variation in the limestones and mudstones indicate that this facies was deposited in a tidal environment. High sedimentation rate and variable salinity (and therefore exclusion of bioturbators and invertebrate scavengers) are interpreted as key elements that led to the excellent preservation of the fossils in this ancient estuarine environment. □Lagerstätte, taphonomy, estuarine, tidal bedding, paleovalley, Carboniferous, Kansas.     

A Comparison of Cortical Proteins in Tetrahymena vorax Microstomes and Macrostomes1

Proteins of surface membranes and surface-related cytoskeletons in Tetrahymena vorax microstomes and macrostomes were compared by one-dimensional SDS polyacrylamide gel electrophoresis to see if protein differences could be detected that correlate with the transformation from one phenotype to the other. Some differences were observed. However, these alterations appear to result from the heat-shock procedure used to synchronize the microstome-to-macrostome transition. The apparent lack of transformationspecific changes in cortical proteins is discussed. Similarities and differences between cytoskeletal proteins of T. pyriformis GL-C and T. vorax are also noted and discussed.     

A LABELED AFFECTIVE MAGNITUDE (LAM) SCALE FOR ASSESSING FOOD LIKING/DISLIKING1

The most widely used scale for assessing food liking or disliking is the 9‐pt hedonic scale. Unfortunately, this affective scale suffers from problems related to unequal scale intervals and the underuse of end categories, which results in a reduced ability to differentiate among extremely well liked or extremely disliked foods. Magnitude estimation avoids these problems while enabling ratio statements to be made about the data. However, it does not provide absolute ratings of liking/disliking and can be difficult for some consumers to use. We report here on the development of a labeled affective magnitude scale (LAM) scale that has advantages over both the 9‐pt hedonic scale and magnitude estimation. Forty‐four semantic labels were scaled for their affective meaning by subjects using modulus‐free magnitude estimation. The geometric mean magnitude estimates obtained for each semantic label were used to construct a series of labeled affective magnitude scales by spacing the labels along a visual analogue scale according to their obtained semantic values. Reliability and sensitivity studies were conducted to assess the effects of alternative semantic and numeric labels. The results of these studies led to the choice of a scale format that uses verbal labels that are consistent with the 9‐pt hedonic scale. The labeled affective magnitude (LAM) scale was compared to the hedonic scale and magnitude estimation in several food preference and acceptability tests. The LAM was shown to have equal reliability and sensitivity to the hedonic scale, provided somewhat greater discrimination among highly liked foods, and resulted in data that were similar to magnitude estimation in terms of the obtained ratios among rated stimuli. The LAM scale was also judged by consumers to be as easy to use as the 9‐pt hedonic scale and significantly less difficult than magnitude estimation.     

The Formation and Development of Adventitious Buds on Potato Sprouts

Potato tubers were pre-sprouted in trays at 10 C for 28 d.The scale leaves at the base of the sprouts were marked andtubers then planted in field soil. Twenty-eight days after plantingan average of three adventitious buds were present per sproutcompared with an average of six below-ground axillary buds.Ten per cent of adventitious buds formed stolons compared withalmost 100 per cent of axillary buds. Similar responses wereseen with tubers pre-sprouted either in the light or dark.