Translocation of Nocturnally Fixed 14C in the Crassulacean Acid Metabolism Epiphyte Tillandsia Usneoides L.

This is the publisher's official version, also available electronically from: http://www.jstor.org/stable/10.2307/2474371.Strands of the Crassulacean acid metabolism (CAM) epiphyte Tillandsia usneoides L. (Spanish moss) were exposed to 14C02 in situ at night and were collected immediately and at intervals of up to 4 0 days. Autoradiographs of the exposed strands were made. The tissue was separated into parts, oxidized, and counted in a liquid scintillation counter. The entire surface of labeled portions of the plant took up 14CC>2. There was very little translocation of 1 4C out of the labeled portion of the strand at 4 0 days. Translocation within the labeled portion occurred from leaves and stems to nodal (meristematic) regions. The results are similar to those found with several other CAM plants

Book review of "Life Strategies of Succulents in Deserts with Special Reference to the Namib Desert"

This is the published version

Growth and Morphological Responses to Irradiance in Three Forest Understory Species of the C4 Grass Genus Muhlenbergia

This is the publisher's version, also available electronically from: http://www.jstor.org/stable/2995468.Three species of the C4 grass genus Muhlenbergia—M. frondosa, M. sobolifera, and M. schreberi— were collected from forest understory sites in northeastern Kansas and grown in a growth chamber at 1,500, 150, and 15-25 fjimol m~2 s - 1 photosynthetic photon flux density (PPFD). Leaf, stem, root, and total biomasses and several morphological and anatomical characteristics were measured after 35-38 days. Results were compared with similar measurements for M. cuspidata collected from exposed prairie sites. Although all species grew maximally at the highest PPFD, M. sobolifera grew equally well at medium PPFD. Few anatomical changes were correlated with changes in PPFD except leaf thickness, which increased with increasing PPFD. The results indicate that, while the understory species of Muhlenbergia can adjust morphologically to some extent to shaded environments, they produce more biomass at higher PPFD

Photosynthetic Responses to Irradiance in Three Forest Understory Species of the C4 Grass Genus Muhlenbergia

This is the publisher's official version, also available electronically from: http://www.jstor.org/stable/2995345Three species of the C4 grass genus Muhlenbergia—M.frondosa, M. sobolifera, and Af. schreberi—were collected from forest understory habitats in Kansas and grown in a growth chamber at 1,500, 150, and 15- 25 |xmol m"2 s"1 photosynthetic photon flux density (PPFD). Assimilation (A), conductance to C02 , intercellular C02 concentration, chlorophyll (chl) concentrations, and photosystem I electron-transport capacity were determined and compared with results for Af. cuspidata, which occurs only in open, prairie areas. All of the shade species exhibited more shade tolerance than the prairie species: they had lower maximum A, saturation of A, and photosystem I electron transport with respect to PPFD, higher quantum yields that increased with decreasing growth PPFD, and increasing chl concentrations with decreasing PPFD

Functional Stomata of the Atmospheric Epiphyte Tillandsia Usneoides L.

This is the publisher's version, also available electronically from: http://www.jstor.org/stable/10.2307/2474260.Although stomatal opening in Tillandsia usneoides is not detectable by light microscopy, the guard cells swell in the dark and in the light in buffers known to stimulate stomatal opening. Abscisic acid or phenylmercuric acetate substantially reduced subsequent nocturnal C 0 2 uptake. Potassium ions were more concentrated in the guard cells in the dark than in the light. The stomata of this CAM epiphyte appear functional: open at night and closed throughout most of the day

Photosynthetic pathway variation in leafy members of two subfamilies of the Cactaceae

Patterns of 24‐h CO2 exchange and diel fluctuations in tissue acid concentrations were measured in leafy and leafless shoots of 10 species in the Pereskioideae and eight species in the Opuntioideae (Cactaceae). The species were selected to represent a range of phylogenetic histories. Leafy shoots of all species in the Pereskioideae exhibited C3 patterns of gas exchange, and net CO2 exchange of leafless stems in all but one species was negative during the day and night. Although nighttime CO2 uptake was not observed in shoots or stems of any of the pereskioid taxa, tissue acidity increased at night to a small degree in leaves of six species and stems of five species, indicative of low levels of CAM‐cycling. In contrast, in leafy shoots of nearly all species in the Opuntioideae, CO2 uptake occurred during the day and the night. Gas‐exchange rates were typically greater during the day. As is typical of CAM, nighttime maximal water use efficiency often greatly exceeded daytime values. Tissue malic acid concentrations increased overnight in leaves and stems of all eight opuntioid species. Examination of the data from a phylogenetic perspective illustrates evidence of low levels of CAM scattered among the primarily C3 members of the more ancestral Pereskioideae. Furthermore, such consideration of the taxa in the more derived Opuntioideae (comparing the genera from most ancestral to most derived, that is, Austrocylindropuntia → Quiabentia → Pereskiopsis → Cylindropuntia) revealed that CAM became increasingly less important in the leaves of the various taxa, whereas this water‐conservative pathway of photosynthesis became increasingly more important in the stems. The results of this study indicate that members of the Pereskioideae should be restricted to moister habitats or must restrict the timing of growth to wet seasons, whereas the observed combinations of the C3 and CAM pathways in the opuntioid taxa should prove beneficial in conserving water in the sporadically arid tropical and subtropical habitats of these plants

C3 Photosynthesis and Crassulacean Acid Metabolism in a Kansas Rock Outcrop Succulent, Talinum calycinum Engelm. (Portulacaceae)

This is the publisher's official version, also available electronically from: http://www.plantphysiol.org/content/73/3/718.full.pdf+html.The potential for Crassulacean acid metabolism (CAM) was investigated in the sandstone outcrop succulent Talinum calycinum in central Kansas. Field studies revealed CAM-Iike diurnal acid fluctuations in these plants. These fluctuations persisted under all moisture and temperature regimes in the laboratory. Despite this CAM-Iike acid metabolism, simultaneous gravimetric determinations of day- and nighttime transpiration rates indicated the presence of a d gas exchange pattern. Subsequent analyses of diurnal CO; and H2O exchange patterns under wellwatered conditions and after 3, 5, and 7 days of drought confirmed these findings, though low rates of nocturnal CO, uptake were observed on the fifth night after continuous drought. Finally, the 6 I 3 C / "C value of this succulent, - 27.8%c, emphasizes the insignificance of any nocturnal CO.. uptake in the lifelong accumulation of carbon in this species. Thus, it is proposed that T. calycinum is a ( \ plant with some C AM characteristics, including the ability to re-fix respiratory COj at night under all moisture regimes, potentially resulting in a conservation of carbon, and occasionally to fix atmospheric CO. at night. These findings may prove to be common among rock outcrop succulents

Correlation Between CAM-Cycling and Photosynthetic Gas Exchange in Five Species of Talinum (Portulacaceae)

This is the publisher's official version, also available electronically from: http:/​/​dx.​doi.​org/​10.​1104/​pp.​96.​4.​1118Photosynthetic gat exchange and malic acid fluctuations were monitored in 69 well-watered plants from five morphologically similar species of Talinum in an investigation of the ecophysiological significance of the Crassulacean acid metabolism (CAM)- cycling mode of photosynthesis. Unlike CAM, atmospheric C03 uptake in CAM-cycling occurs exclusively during the day; at night, the stomata are closed and respiratory C 0 2 is recaptured to form malic add. All species showed similar patterns of day-night gas exchange and overnight malic acid accumulation, confirming the presence of CAM-cycling. Species averages for gas exchange parameters and malic acid fluctuation were significantly different such that the species with the highest daytime gas exchange had the lowest malic acid accumulation and vice versa. Also, daytime CO2 exchange and transpiration were negatively correlated with overnight malic acid fluctuation for all individuals examined together, as well as within one species. This suggests that malic acid may effect reductions in both atmospheric CO: uptake and transpiration during the day. No significant correlation between malic acid fluctuation and water-use efficiency was found, although a nonsignificant trend of increasing water-use efficiency with increasing malic acid fluctuation was observed among species averages. This study provides evidence that C 0 2 recycling via malic acid is negatively correlated with daytime transpirational water losses In well-watered plants. Thus, CAM-cycling could be important for survival In the thin, frequently desiccated soils of rock outcrops on which these plants occur

Physiological and Anatomical Responses to Water Deficits in the CAM Epiphyte Tillandsia Ionantha (Bromeliaceae)

Although physiological responses to drought have been examined in several species of epiphytic bromeliads, few have included a comprehensive methodological approach to the study of the carbon and water relations of a single species undergoing drought stress. Thus, physiological and anatomical responses to an imposed drought treatment were examined in the atmospheric Crassulacean acid metabolism (CAM) epiphyte Tillandsia ionantha. From 0 through 20 d without water, nocturnal malic acid accumulation and CO2 uptake rates did not change despite a 17% reduction in relative water content. In addition, water potentials averaged -0.40 MPa and, unlike leaf water content, did not decline. The avoidance of further declines in leaf water content was attributed to the restriction of stomatal opening to the night (a characteristic feature of CAM), to low stomatal densities and small stomatal pores, and to a thick boundary layer resulting from a dense foliar trichome cover. The maintenance of high physiological activity during the first 20 d of the drought treatment was most likely a result of the high water potentials in the chlorenchyma, which were attributed, in part, to water movement from the water-storage parenchyma (= "hydrenchyma") to the chlorenchyma. Nocturnal malic acid accumulation and the rate of net CO2 exchange declined in a linear fashion from 30 to 60 d without water, as did leaf water potential and osmotic potential. During this time, CO2 recycling increased from ca. 20% to nearly 75%. Though declining throughout this later stage of the drought treatment, metabolic activity remained relatively high, possibly as a result of the observed osmotic adjustment as well as a potentially high cell wall elasticity

Unusual Water Relations in the CAM Atmospheric Epiphyte Tillandsia Usneoides L. (Bromeliaceae)

This is the publisher's version, also available electronically from: http://www.jstor.org/stable/2995179.Past studies have reported two unusual aspects of the water relations of the atmospheric CAM epiphyte Tillandsia usneoides L. (Bromeliaceae): a drought stimulation of nocturnal C02 uptake, and nocturnal absorption of water vapor. Contrary to past reports, a 10-d drought did not stimulate nocturnal C02 uptake in this species. On the other hand, previous reports of nocturnal water vapor absorption were confirmed in situ throughout a year, although tissue hydration from this source was insufficient to offset daytime water loss. Deposition of dew on the plants was never observed in the field. It is hypothesized that the unusual nature of the water relations of T. usneoides is attributable to the interactions between two "pools" of water and the external atmosphere. The dense indumentum of trichomes obscuring the surface of this epiphyte comprises one pool and is most likely responsible for rapid hydration early in the night and dehydration early in the day. In addition, stomata control water loss from the living mesophyll cells, the second pool, for the remainder of the night. The high rates of water loss observed throughout the day when stomata are closed probably result from leakage through the trichomes