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Turgor and osmotic relations of the desert shrub Larrea tridentata (1986)

MEINZER, F. C. ; RUNDEL, P. W. ; SHARIFI, M. R. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 9 (1986), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract Leaf water relations characteristics of creosote bush, Larrea tridentata, were studied in view of previous reports that its leaves commonly experience zero or negative turgor under dry conditions. Leaf turgor loss point (〈inlineGraphic alt="inline image" href="urn:x-wiley:01407791:PCE467:PCE_467_mu1" location="equation/PCE_467_mu1.gif"/〉) was determined by a pressure-volume method for samples subjected to a hydration procedure and for untreated samples. Hydration caused 〈inlineGraphic alt="inline image" href="urn:x-wiley:01407791:PCE467:PCE_467_mu1" location="equation/PCE_467_mu1.gif"/〉 to increase by as much as 3 M Pa. Hydration of samples also caused changes in other leaf water relations characteristics such as symplastic solute content, tissue elasticity and symplasmic water fraction, but total leaf solute content was unchanged. Comparison of our field plant water potential data with values of 〈inlineGraphic alt="inline image" href="urn:x-wiley:01407791:PCE467:PCE_467_mu1" location="equation/PCE_467_mu1.gif"/〉 obtained by the two methods resulted in predictions of turgor loss during part or all of a diurnal cycle based on hydrated samples, and turgor maintenance (at least 0.3 MPa) based on untreated samples. Pooled data for 〈inlineGraphic alt="inline image" href="urn:x-wiley:01407791:PCE467:PCE_467_mu1" location="equation/PCE_467_mu1.gif"/〉 obtained from both partially hydrated and untreated samples showed that L. tridentata maintains fairly constant levels of turgor over a wide range of leaf water potential. Dilution of cell contents by apoplastic water introduced significant errors in psychrometric determinations of osmotic potential in both frozen and thawed leaf tissue and expressed cell sap. Use of these values of osmotic potential resulted in predictions of zero turgor at all plant water potentials measured in the field.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3040.1986.tb01762.x

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Effects of manipulation of water and nitrogen regime on the water relations of the desert shrub Larrea tridentata (1988)

Meinzer, F. C. ; Sharifi, M. R. ; Nilsen, E. T. ; [et al.]

Springer

Oecologia 77 (1988), S. 480-486

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ISSN: 1432-1939

Keywords: Larrea tridentata ; Water relations ; Nitrogen fertilization ; Stomata ; Canopy transpiration

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Water and nitrogen regimes of Larrea tridentata shrubs growing in the field were manipulated during an annual cycle. Patterns of leaf water status, leaf water relations characteristics, and stomatal behavior were followed concurrently. Large variations in leaf water status in both irrigated and nonirrigated individuals were observed. Predawn and midday leaf water potentials of nonirrigated shrubs were lowest except when measurements had been preceded by significant rainfall. Despite the large seasonal variation in leaf water status, reasonably constant, high levels of turgor were maintained. Pressure-volume curve analysis suggested that changes in the bulk leaf osmotic potential at full turgor were small and that nearly all of the turgor adjustment was due to tissue elastic adjustment. The increase in tissue elasticity with increasing water deficit manifested itself as a decrease in the relative water content at zero turgor and as a decrease in the tissue bulk elastic modulus. Because of large hydration-induced displacement in the osmotic potential and relative water content at zero turgor, it was necessary to use shoots in their natural state of hydration for pressure-volume curve determinations. Large diurnal and seasonal differences in maximum stomatal conductance were observed, but could not easily be attributed to variations in leaf water potential or leaf water relations characteristics such as the turgor loss point. The single factor which seemed to account for most of the diurnal and seasonal differences in maximum stomatal conductance between individual shrubs was an index of soil/root/ shoot hydraulic resistance. Daily maximum stomatal conductance was found to decrease with increasing soil/root/ shoot hydraulic resistance. This pattern was most consistent if the hydraulic resistance calculation was based on an estimate of total canopy transpiration rather than the more commonly used transpiration per unit leaf area. The reasons for this are discussed. It is suggested that while stomatal aperture necessarily represents a major physical resistance controlling transpiration, plant hydraulic resistance may represent the functional resistance through its effects on stomatal aperture.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00377263

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Carbon isotope composition in relation to leaf gas exchange and environmental conditions in Hawaiian Metrosideros polymorpha populations (1992)

Meinzer, F. C. ; Rundel, P. W. ; Goldstein, G. ; [et al.]

Springer

Oecologia 91 (1992), S. 305-311

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ISSN: 1432-1939

Keywords: Carbon isotope ratio ; Gas exchange ; Metrosideros ; Nitrogen-use efficiency ; Water-use efficiency ; Bog

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Carbon isotope composition, photosynthetic gas exchange, and nitrogen content were measured in leaves of three varieties of Metrosideros polymorpha growing in sites presenting a variety of precipitation, temperature and edaphic regimes. The eight populations studied could be divided into two groups on the basis of their mean foliar δ13C values, one group consisting of three populations with mean δ13C values ca.-26‰ and another group with δ13C values ca.-28‰. Less negative δ13C values appeared to be associated with reduced physiological availability of soil moisture resulting from hypoxic conditions at a poorly drained high elevation bog site and from low precipitation at a welldrained, low elevation leeward site. Gas exchange measurements indicated that foliar δ13C and intrinsic wateruse efficiency were positively correlated. Maximum photosynthetic rates were nearly constant while maximum stomatal conductance varied substantially in individuals with foliar δ13C ranging from-29 to-24‰. In contrast with the patterns of δ13C observed, leaf nitrogen content appeared to be genetically determined and independent of site characteristics. Photosynthetic nitrogenuse efficiency was nearly constant over the range of δ13C observed, suggesting that a compromise between intrinsic water- and N-use efficiency did not occur. In one population variations in foliar δ13C and gas exchange with leaf cohort age, caused the ratio of intercellular to atmospheric partial pressure of CO2 predicted from gas exchange and that calculated from δ13C to be in close agreement only in the two youngest cohorts of fully expanded leaves. The results indicated that with suitable precautions concerning measurement protocol, foliar δ13C and gas exchange measurements were reliable indicators of potential resource use efficiency by M. polymorpha along environmental gradients.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00317617

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Influences of microclimatic conditions and water relations on seasonal leaf dimorphism of Prosopis glandulosa var. torreyana in the Sonoran Desert, California (1986)

Nilsen, E. T. ; Sharifi, M. R. ; Rundel, P. W. ; [et al.]

Springer

Oecologia 69 (1986), S. 95-100

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Seasonal measurements of microclimatic conditions were compared to seasonal indices of leaf structural components and plant water relations in Prosopis glandulosa var. torryana. P. glandulosa had two short periods of leaf production which resulted in two distinct even aged cohorts of leaves. The two leaf cohorts (summer, winter) were concurrent in the summer and fall, contrasting to previous studies on other species in which one leaf form replaces a previous leaf type. The structural characteristics of these two cohorts differed significantly in two replicate year cycles. The leaves of the spring cohort were larger in weight and area but similar to the summer cohort in specific leaf weight and leaflet number. The second growth period leaves constituted only a small proportion of the total plant leaf area. The dimorphism between the two cohorts was best associated with plant water relations and not energy load. Second growth period leaves maintained turgor to greater water deficits but lost turgor at higher leaf water potentials. Seasonal osmotic adjustment occurred for first growth period leaves but not second growth period leaves. The small leaves produced during the hot climate were most likely the result of low turgor potential during development rather than an adaptation to tolerate stressful environments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00399043

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Photosynthesis by inflated pods of a desert shrub, Isomeris arborea (1991)

Goldstein, G. ; Sharifi, M. R. ; Kohorn, L. U. ; [et al.]

Springer

Oecologia 85 (1991), S. 396-402

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ISSN: 1432-1939

Keywords: Isomeris arborea ; Fruit photosynthesis ; Recycling of internally supplied CO2 ; Carbon balance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The photosynthetic capacity and carbon metabolism of the fruits of Isomeris arborea (Capparidaceae), an evergreen shrub endemic to the desert and coastal habitats of Southern California and Baja California, are described. The inflated structure of the pods of I. arborea provides a model system for experimental studies of fruit photosynthesis in native plants since the gas concentration of the internal space can be manipulated and monitored separately from the external pod environment. CO2 released by seed respiration is partially contained in the inner gas space of the pods, resulting in an elevated CO2 environment inside the fruit (500 to 4000 μmol mol−1 depending on the stage of fruit development). A portion of this CO2 is assimilated by the inner layers of the pericarp, but a larger fraction leaks out. The photosynthetic layers of the pericarp use two different sources of CO2: the exocarp fixes exogenous CO2 while the endocarp fixes CO2 released by seed respiration into the pod cavity. Even though the total weight of the fruit increases during development, the combined rates of fixation of externally and internally supplied CO2 remained constant (10–11 μmol CO2 pod−1 h−1). After the pods attain maximum volume, the major change in gas exchange that takes place during fruit growth is a gradual increase in the amount of respiratory CO2 released by the seeds. This shifts the CO2 balance of the fruit from positive, in young fruits, to negative in mature fruits. Pericarp photosynthesis helped support not only the cost of fruit maintenance, but also the cost of fruit growth, particularly during the first stages of fruit development. During later fruiting stages insufficient carbon is fixed to fully supply either respiration or growth.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00320616

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Water relations of stem succulent trees in north-central Baja California (1990)

Nilsen, E. T. ; Sharifi, M. R. ; Rundel, P. W. ; [et al.]

Springer

Oecologia 82 (1990), S. 299-303

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ISSN: 1432-1939

Keywords: Succulent ; C3 trees ; Capacitance ; Baja California ; Idria collumnaris

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Water relations of several stem succulent trees were measured in north-central Baja California in comparisons to other growth forms in the same habitat. Our research concentrated on three stem succulent species (Idria collumnaris, Pachycormus discolor and Bursera microphylla) each with a different succulent stem morphology. The stem succulent trees had 1 to 4 kg H2O/m3 of trunk while the other trees and shrubs in the same habitat had 0.6 to 0.8 kg H2O/m3. The diurnal and seasonal variation in leaf water potential was small for the stem succulent species in comparison to deciduous and evergreen species as a consequence of the stem-water, buffering capacity. In addition, the leaf conductance of the stem succulent species was low (60 mmol m−2 s−1) and yet, the leaf conductance decreased through the day similar to adjacent evergreen and deciduous species. The leaves of the stem succulent trees lost turgor at low saturated water deficits (0.06 to 0.14), had comparatively high osmotic potentials, and high values of elastic modulus in comparison to adjacent evergreen and deciduous species. The stem acts as an important buffering mechanism allowing for the maintenance of leaf turgor in these stem succulent trees. The low transpiration rates of the stem succulent trees may be a mechanism to minimize leaf saturated water deficit and extend leaf longevity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00317474

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Estimates of N2-fixation from variation in the natural abundance of 15N in Sonoran desert ecosystems (1983)

Shearer, G. ; Kohl, D. H. ; Virginia, R. A. ; [et al.]

Springer

Oecologia 56 (1983), S. 365-373

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The 15N abundance of tissues of five Prosopis specimens at our primary study site (a Prosopis woodland at Harper's Well in the Sonoran desert of Southern California) was determined over two growing seasons 1980 and 1981. The 15N abundance of soil and of tissues of presumed non-N2-fixing (control) plants was also measured. Prosopis tissues were significantly lower in 15N than either soil N or corresponding tissues of presumed non-N2-fixing plants which derive their N entirely from soil. Soil N was also significantly higher in 15N than atmospheric N2. We conclude that it is feasible to use variations in the natural abundance of 15N as an index of N2-fixation in this kind of ecosystem, and that N2-fixation is of considerable importance to Prosopis growing at this site. We also determined the 15N abundance of leaf tissue of presumed N2-fixing and control plants growing at the same site at six additional sites (five in the Sonoran desert of southern California and one in Baja California, Mexico near the town of Catavina). Four of these additional sites were dominated by Prosopis and two were mixed communities. There were statistically significant differences between the 15N abundances of the pooled legume population and control plants at all sites, although not every legume specimen exhibited this difference. From 15N abundance data we estimated the fractional contribution of biologically fixed N to the N economy of desert legumes. We concluded that N2-fixation is very important to Prosopis at six of seven sites in the Sonoran Desert. At the site where Prosopis did not appear to be fixing N2, N2-fixation was important only for legumes of the sub-family Papilionoideae, Lupinus, Dalea, Astragalus and Lotus.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00379714

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Seasonal dynamics of nitrogen cycling for a Prosopis woodland in the Sonoran Desert (1982)

Rundel, P. W. ; Nilsen, E. T. ; Sharifi, M. R. ; [et al.]

Springer

Plant and soil 67 (1982), S. 343-353

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ISSN: 1573-5036

Keywords: Desert woodland ; N-cycling ; N2fixation ; Prosopis glandulosa ; Sonoran Desert

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Description / Table of Contents: Resumen Los bosques de Prosopis en el desierto Sonorense tienen niveles de producción de biomasa (parte aérea) y productividad mucho mayores que las predecibles para comunidades de plantas de desierto con muy bajos niveles de precipitación. Los bosques freatofiticos deP. glandulosa cerca del Mar de Salton, California, producen 13 000 kg ha−1 de biomasa aérea con una productividad 3700 kg ha−1 año−1. Tan alto nivel de productividad es posible porque Prosopis no es afectado por los factores que limitan la aprovechabilidad de agua y nitrógeno. Los primeros 60 cm del perfil del suelo bajo el dosel de Prosopis contienen 1020 g m−2 de nitrógeno total, el 25% existe en la forma de nitrato. Tales acumulaciones de nitrógeno pueden ser el resultado de la fijación simbiótica activa. Los primeros valores estimados sugieren que son fijados entre 25–30 kg N ha−1 año−1 en estos bosques. Puesto que Prosopis cubre solamente 34% de esta área y sus recursos de agua no son limitantes, puede ser posible la obtención de mayores niveles de fijación de nitrógeno y productividad de los cultivos si se manejan con mayores densidades.

Notes: Abstract Prosopis woodlands in the Sonoran Desert have levels of above-ground biomass and productivity much higher than those predicted for desert plant communities with such low levels of precipitation. A stand ofP. glandulosa near the Salton Sea, California, has 13,000 kg ha−1 aboveground biomass and a productivity of 3700 kg ha−1 yr−1. Such a high level of productivity is possible because Prosopis is decoupled from the normal limiting factors of water and nitrogen availability. Soil nitrogen contents for the upper 60 cm of soil beneath Prosopis canopies have 1020 g m−2 total nitrogen, 25 per cent of which is in the form of nitrate. Such accumulations of nitrogen may be the result of active symbiotic nitrogen fixation. Early estimates suggest that about 25–30 kg N ha−1 yr−1 is fixed in these stands. Since Prosopis covers only 34% of the ground surface and its water resources are not limiting, much higher levels of nitrogen fixation and productivity may be possible in managed stands at greater densities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02182781

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