bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth responses of individual roots of Opuntia ficus‐indica to salinity
Authors: GERSANI M. , GRAHAM E. A. , NOBEL P. S. 
Published: April 2006

ABSTRACTResponses of individual roots of the widely cultivated cactus Opuntia ficus‐indica to salinity stress were evaluated using a split‐root system. Three roots from a plant with at least 20 roots were isolated from the remainder of the root system and exposed to 0, 30 or 100 mol m‐3 NaCl for up to 28 d. Cortical cells became shorter and lateral root development was substantially reduced as salinity increased. Compared with the control, the increase in dry weight for the isolated roots was reduced 40% by 30 mol m‐3 NaCl and 93% by 100mol m‐3 NaCl. The sodium content of roots increased only two‐fold with increasing salinity. Respiration rates of roots exposed to 30 or 100 mol m‐3 NaCl were higher than those of the control. Carbon accumulation in roots measured 2 d after exposing shoots to 14CO2 was not initially affected by 30 mol m‐3 NaCl but was substantially reduced at 100 mol m‐3 NaCl. Thus, roots exposed to short periods of moderate salinity stress maintained sufficient carbon sink strength for continued growth of the roots. Moreover, increased salinity led to decreased efficiency of carbon usage for the expansion of root surface area.
Stored xylem sap from wheat and barley in drying soil contains a transpiration inhibitor with a large molecular size
Authors: MUNNS R. , PASSIOURA J. B. , MILBORROW B. V. , JAMES R. A. , CLOSE T. J. 
Published: April 2006

ABSTRACTXylem sap was collected from wheat and barley growing in a drying soil, and the effect of the sap on transpiration was detected by a bioassay with detached wheat leaves. The inhibitory activity of fresh sap was small, and could be largely accounted for by the abscisic acid content (about 2×10‐5mol m‐3). When fresh sap was stored at ‐20°C for several days, the activity increased. Maximum activity developed after a week. This increase in activity was due to a compound that increased in size with storage at ‐20°C. When fresh sap was fractionated with filters of different molecular size exclusion characteristics, and the separated fractions stored at ‐20°C for a week, activity developed only in the fraction containing compounds smaller than 0·3 kDa. However, when sap already stored at ‐20°C was fractionated, activity was only in fractions containing compounds larger than 0·3 kDa. The increase in activity and in size did not occur with storage in liquid nitrogen (‐196°C) or at ‐80°C. These results suggest that storage at ‐20°C causes the aggregation or polymerization of a small compound with low activity to form a large compound with high activity. This change is not catalysed by an enzyme because it can occur in a fraction from which molecules larger than 0·3 kDa are removed. It is probably promoted by high solute concentrations when ice crystals form. Sap collected from plants in soils of high water potential had little or no activity after storage at ‐20°C.
Growth and onto‐morphogenesis of soybean (Glycine max Merril) in an open, naturally CO2‐enriched environment
Authors: MIGLIETTA F. , RASCHI A. , RESTI R. , BADIANI M. 
Published: April 2006

ABSTRACTSprings emitting carbon dioxide are frequent in Central Italy and provide a way of testing the response of plants to CO2 enrichment under natural conditions. Results of a CO2 enrichment experiment on soybean at a CO2 spring (Solfatara) are presented. The experimental site is characterized by significant anomalies in atmospheric CO2 concentration produced by a large number of vents emitting almost pure CO2 (93%) plus small amounts of hydrogen sulphide, methane, nitrogen and oxygen. Within the gas vent area, plants were grown at three sub‐areas whose mean CO2 concentrations during daytime were 350,652 and 2370 μmol mol‐1, respectively. Weekly harvests were made to measure biomass growth, leaf area and ontogenetic development. Biomass growth rate and seed yield were enhanced by elevated CO2. In particular, onto‐morphogenetic development was affected by elevated CO2 with high levels of CO2 increasing the total number of main stem leaf nodes and the area of the main stem trifoliolate leaves. Biochemical analysis of plant tissue suggested that there was no effect of the small amounts of H2S on the response to CO2 enrichment. Non‐protein sulphydryl compounds did not accumulate in leaf tissues and the overall capacity of leaf extracts to oxidize exogenously added NADH was not decreased. The limitations and advantages of experimenting with crop plants at elevated CO2 in the open and in the proximity of carbon dioxide springs are discussed.
Fructose‐containing carbohydrates in the tuberous root of Gomphrena macrocephala St.‐Hil. (Amaranthaceae) at different phenological phases
Authors: VIEIRA C. C. J. , FIGUEIREDO‐RIBEIRO R. C. L. 
Published: April 2006

ABSTRACT Gomphrena macrocephala St.‐Hil. (Amaranthaceae) is a perennial herb that grows spontaneously in the cerrado and is characterized by well‐defined phenological phases throughout the year. Soluble carbohydrates are the main reserve compounds of the tuberous root and constitute approximately 50% of the dry weight. These sugars were partially characterized as fructans forming a single homologous series, different from inulin, the most common fructan of dicotyledons. The mean molecular weight of polysaccharides was high and reached 37 kDa in the dormant phase. Fructan spherocrystals were detected in the tuberous root after treatment with ethanol, being associated with the parenchyma of secondary xylem. The content, composition and mean molecular weight of fructans were related to phenology. In late dormancy, there was a marked increase in monosaccharides, particularly fructose, and a concomitant decline of polysaccharides, probably as a result of fructan breakdown. During sprouting and in the vegetative phase, the contents of oligosaccharides and low molecular weight polysaccharides increased. A gradual rise in the molecular weight of polysaccharides occurred during the reproductive phase and at early dormancy, concurrently with decreasing levels of oligosaccharides. The capacity of G. macrocephala to accumulate readily accessible sugars, such as fructans, instead of starch, in response to environmental changes, may be of considerable advantage, since the cerrado is often subjected to seasonal drought and burnings.
Photosynthetic acclimation to shade: probing the role of phytochromes using photomorphogenic mutants of tomato
Authors: SMITH H. , SAMSON G. , FORK D. C. 
Published: April 2006

ABSTRACTPhotomorphogenic mutants of tomato were used to probe the possible involvement of phytochrome A in photosynthetic acclimation to shade. Plants of wild‐typeLycopersicon esculentum, the near isogenic mutantsaurea(au, deficient in phytochrome A, and also possibly other phytochromes) andhigh pigment(hp, exhibiting exaggerated photomorphogenic responses), and theau/hpdouble mutant were grown in a greenhouse under either unfiltered daylight, or daylight attenuated by neutral density filters or green filters that simulated the spectral effects of vegetation shade. Growth and photosynthetic parameters were measured over a growing period of 15 d. Typical effects of simulated vegetation shade on extension growth were observed only in the wild‐type andhpstrains; the presence of theaulesion resulted in reduced capacity to respond to vegetation shade by increased extension. Photosynthetic light saturation curves obtained using infrared gas analysis at 15 d indicated that neither theaunor thehpmutations caused serious reductions in maximum net photosynthetic rate in plants acclimated to full daylight, although theau/hpdouble mutant showed a significantly reduced maximum rate. In the wild‐type andhpstrains grown under both neutral and simulated vegetation shade, the photosynthetic light saturation curves were similar. Plants with theaulesion showed a significantly lower capacity to acclimate to vegetation shade, as seen by their reduced maximum rate of net photosynthesis. However,in situmeasurements of photosynthetic rate in the greenhouse were indistinguishable between the four strains. Thylakoid stoichiometry measurements revealed a very large increase in PSII/PSI ratio under simulated vegetation shade as compared with either unfiltered daylight or neutral density shade. These increases were not diminished in the phytochrome‐deficientaustrains, and were even larger in thehpstrains. The results indicate that theaulesion has little effect on the capacity of tomato to exhibit photoadaptation to simulated vegetational shade when measured at the thylakoid level. On the other hand, net leaf photosynthesis under vegetation shade can be significantly affected by the phytochrome deficiency caused by theaumutation, implying a possible role for one or more of the phytochromes in photoadaptation at the leaf level.
Modelling carbon isotope fractionation in tree rings based on effective evapotranspiration and soil water status
Authors: DUPOUEY J.‐L. , LEAVITT S. , CHOISNEL E. , JOURDAIN S. 
Published: April 2006

ABSTRACTEnvironmental influences on carbon isotope fractionation in tree rings require further elucidation in order to use this parameter as a biological marker of climatic variations. δ13C values in tree‐ring cellulose of beech (Fagus sylvaticaL.) were analysed for the period from 1950 to 1990. A bioclimatic model of water balance was used to give the actual evapotranspiration as well as the soil water content on a daily basis. δ13C shows a significant decrease from –24·5‰ to –25‰ over this period. Internal CO2concentration changes from 200 to 220 ppm in relation with the rise of atmospheric CO2. Beside a slight non‐significant inter‐individual variation, a large year‐to‐year variation exists. The relative extractable soil water of July, combined with the value of δ13C for the previous year, predicts as much as 70% of this variance. Air temperature or precipitation accounted for less variation. δ13C is strongly correlated with basal area increment, but appeared a more reliable indicator of water status at the stand level.
Solute analysis and water relations of gametophyte mutants tolerant to NaCl in the fern Ceratopteris richardii
Authors: VOGELIEN D. L. , HICKOK L. G. , AUGÉ R. M. , STODOLA A. J. W. , HENDRIX D. 
Published: April 2006

ABSTRACTThe stl1 and stl2 mutations confer low and high levels of NaCl tolerance to gametophytes of the fern Ceratopteris richardii, respectively. As an initial characterization of these mutations, the levels of various organic solutes, tissue ion content and water relations were examined in the wild‐type and mutant strains in the absence and presence of 60 mol m‐3 NaCl stress (a level which results in a 20, 15 and 0% reduction in gametophyte growth in the wild‐type, stl1 mutant and stl2 mutant, respectively). All strains exhibited major changes in organic and inorganic solute levels and water relations in response to 60 mol m‐3 NaCl stress. Differences in organic solute levels and water relations between the wild‐type and mutant strains in the absence and in response to 60 mol m‐3 NaCl stress were minimal. Analysis of tissue ion content showed that stl1 was associated with a slight reduction in Na+ accumulation during 60 mol m‐3 NaCl stress. stl2 was associated with (1) higher constitutive levels of K+ and (2) continued selective accumulation of K+ and reduced accumulation of Na+ during 60 mol m‐3 NaCl stress. A K+/Na+ ratio close to 1 was observed in the wild‐type during 60 mol m‐3 NaCl stress, while higher ratios were detected in stl1 and stl2 (1·7 and 4·0, respectively). The findings of this study suggest that the tolerance imparted by stl1 and stl2 is associated with altered ion accumulation during NaCl stress, rather than an enhanced ability to accumulate organic solutes to be used for osmotic adjustment of the cytoplasm.
Immunocytochemical localization of indole‐3‐acetic acid in primary roots of Zea mays
Authors: SHI L. , MILLER I. , MOORE R. 
Published: April 2006

ABSTRACTColloidal gold‐labelled antibody was used to localize indole‐3‐acetic acid in caps of primary roots of Z. mays cv. Kys. Gold particles accumulated on the nucleus, vacuoles, mitochondria, and some dictyosomes and dictyosome‐derived vesicles. This is the first localization of indole‐3‐acetic acid in dictyosomes and dictyosome‐derived vesicles and indicates that dictyosomes and vesicles constitute a pathway for indole‐3‐acetic acid movement in and secretion from root cap cells. Our findings provide cytochemical evidence to support the hypothesis that indole‐3‐acetic acid plays an important role in root gravitropism.
The effect of a long‐term water stress on the metabolism and emission of terpenes of the foliage of Cupressus sempervirens
Authors: YANI A. , PAULY G. , FAYE M. , SALIN F. , GLEIZES M. 
Published: April 2006

ABSTRACTThe effects of long‐term water stress on water and terpene contents of the foliage of Cupressus sempervirens were studied. A great deal of water was lost over 2 months before a remarkable stabilization. A strong decrease of all the classes of terpenes accompanied this dehydration. Mono‐ and sesquiterpene hydrocarbons and free terpenols were almost entirely metabolized, whereas esters and terpene glycosides rose slightly and remained at a constant level when the water content had stabilized. Although a significant part of the mono‐ and sesquiterpene hydrocarbons was emitted in the early stage of stress application, the major part was used by the plant in response to the drought conditions.
Mathematical models of the photosynthetic response of tree stands to rising CO2 concentrations and temperatures
Authors: McMURTRIE R. E. , WANG Y.‐P. 
Published: April 2006

ABSTRACTTwo published models of canopy photosynthesis, MAESTRO and BIOMASS, are simulated to examine the response of tree stands to increasing ambient concentrations of carbon dioxide (Ca) and temperatures. The models employ the same equations to described leaf gas exchange, but differ considerably in the level of detail employed to represent canopy structure and radiation environment. Daily rates of canopy photosynthesis simulated by the two models agree to within 10% across a range of CO2 concentrations and temperatures. A doubling of Ca leads to modest increases of simulated daily canopy photosynthesis at low temperatures (10% increase at 10°C), but larger increases at higher temperatures (60% increase at 30°C). The temperature and CO2 dependencies of canopy photosynthesis are interpreted in terms of simulated contributions by quantum‐saturated and non‐saturated foliage. Simulations are presented for periods ranging from a diurnal cycle to several years. Annual canopy photosynthesis simulated by BIOMASS for trees experiencing no water stress is linearly related to simulated annual absorbed photosynthetically active radiation, with light utilization coefficients for carbon of ɛ= 1.66 and 2.07g MJ−1 derived for Ca of 350 and 700 μmol mol−1, respectively.
Estimating transpiration from 6‐year‐old Eucalyptus grandis trees: development of a canopy conductance model and comparison with independent sap flux measurements
Authors: DYE P. J. , OLBRICH B. W. 
Published: April 2006

ABSTRACTDaily patterns of stomatal conductance (gs), xylem pressure potential (P) and canopy microclimatic variables were recorded on 11 sample days as part of a one‐year study of the water use of Eucalyptus grandis Hill ex Maiden in the eastern Transvaal, South Africa. Measured gs was found to be largely controlled by quantum flux density (Q) and ambient vapour pressure deficit (D). Canopy conductance (gc) was determined for hourly intervals using gs measurements and leaf areas in four different canopy levels. A simple model was constructed to allow the prediction of gc and transpiration from Q, D and season of year. The model was used to estimate transpiration rates from 10 trees in a later study of similarly‐aged E. grandis trees, in which sap flow in each tree was measured using the heat pulse velocity (HPV) technique. Five of the trees were monitored on a summer day and five on a winter day. Correspondence between HPV sap flow and modelled transpiration was good for the summertime comparisons, but measured winter‐time sap flow rates were underestimated by the model, especially under conditions of high sap flow. The discrepancy is believed to result from having insufficient data from the conductance study to describe the response of gs to relatively high D in winter. Marked variation in transpiration per unit leaf area indicates that a relatively large number of trees must be sampled for the HPV technique to be used to obtain a mean rate for an entire stand in winter.
Daily fluctuations of titratable acidity, content of organic acids (malate and citrate) and soluble sugars of varieties and wild relatives of Ananas comosus L. growing under natural tropical conditions
Authors: MEDINA E. , POPP M. , OLIVARES E. , JANETT H.‐P. , LÜTTGE U. 
Published: April 2006

ABSTRACTThe genus Ananas has its centre of origin in northern South America. In this area, several varieties of Ananas comosus are widely cultivated, and a number of wild species are found growing under variable conditions of light intensity, soil fertility and water availability. Here we report detailed daily courses of titratable acidity, and malate, citrate and free‐sugars content of several cultivated varieties of A. comosus and of A. ananassoides, a closely related species growing on granitic rock‐outcrops in southern Venezuela. Day‐night oscillations of both malate and citrate were detected in plants growing under full sun, but malate was by far the most important organic anion associated with CAM performance in ail populations sampled. Fructose was the dominant compound in the neutral fraction, but only sucrose showed a consistent inverse relation with the cycle of titratable acidity. The diel oscillations of free sugars measured were not always enough to account for the amount of organic anions accumulated during the night. Plants cultivated under shady conditions always showed a lower night‐time increase in titratable acidity and organic acids, and also smaller oscillations in the amount of free sugars than sun exposed plants. In all populations growing under full sun, osmolality increased during the night, but it was not always possible to explain these changes on the basis of variations in molar concentrations of organic acids and sugars. Besides, no diel variations in the cations K+, Ca2+ and Mg2+ were detected. K+ was always the dominant cation (K/Ca ratios ∼ 19), while Mg2+ was always higher than Ca2+ (Mg/Ca ∼ 2).
The functional significance of palisade tissue: penetration of directional versus diffuse light
Authors: VOGELMANN T. C. , MARTIN G. 
Published: April 2006

ABSTRACTLight gradients were measured in leaves that had different types of anatomical development of the mesophyll but similar pigment content. Leaves of the legume, Thermopsis montana, had columnar palisade and spongy mesophyll whereas leaves of the monocot, Smilacina stellata, had spongy mesophyll only. Light gradients were measured at 550 nm in both types of leaves when they were irradiated with collimated or diffuse light. When irradiated with collimated light, light gradients were steeper in leaves with spongy mesophyll in comparison to those that had palisade tissue. On the other hand, light gradients were similar between both leaf types when they were irradiated with diffuse light. Thus, columnar palisade cells facilitated the penetration of collimated light over diffuse light. These results suggest that palisade tissue may help distribute light more uniformly to chloroplasts within the leaf. Moreover, the functional significance of palisade tissue may be related to the amount of collimated light within the natural environment.
Influence of ultraviolet‐B (UV‐B) radiation on photosynthetic and growth characteristics in field‐grown cassava (Manihot esculentum Crantz)
Authors: ZISKA L. H. , TERAMURA A. H. , SULLIVAN J. H. , McCOY A. 
Published: April 2006

ABSTRACTThe effects of ultraviolet‐B (UV‐B between 290 and 320 nm) on photosynthesis and growth characteristics were investigated in field grown cassava (Manihot esculentum Crantz). Plants were grown at ambient and ambient plus a 5.5kJ m−2 d−1 supplementation of UV‐B radiation for 95 d. The supplemental UV‐B fluence used in this experiment simulated a 15% depletion in stratospheric ozone at the equator (0°N). Carbon dioxide exchange, oxygen evolution, and the ratio of variable to maximum fluorescence (Fv/Fm) were determined for fully expanded leaves after 64–76 d of UV‐B exposure. AH plants were harvested after 95 d of UV‐B exposure, assayed for chlorophyll and UV‐B absorbing compounds, and separated into leaves, petioles, stems and roots. Exposure to UV‐B radiation had no effect on in situ rates of photosynthesis or dark respiration. No difference in the concentration of UV‐B absorbing compounds was observed between treatments. A 2‐d daytime diurnal comparison of Fv to Fm ratios indicated a significant decline in Fv/Fm ratios and a subsequent increase in photoinhibition under enhanced UV‐B radiation if temperature or PPF exceeded 35°C or 1800μmol m−2 s−1, respectively. However, UV‐B effects on fluorescence kinetics appeared to be temporal since maximal photosynthetic rates as determined by oxygen evolution at saturated CO2 and PPF remained unchanged. Although total biomass was unaltered with UV‐B exposure, alterations in the growth characteristics of cassava grown with supplemental UV‐B radiation are consistent with auxin destruction and reduced apical dominance. Changes in growth included an alteration of biomass partitioning with a significant increase in shoot/root ratio noted for plants receiving supplemental UV‐B radiation. The increase in shoot/root ratio was due primarily to a significant decrease in root weight (–32%) with UV‐B exposure. Because root production determines the harvest‐able portion of cassava, UV‐B radiation may still influence the yield of an important tropical agronomic species, even though photosynthesis and total dry biomass may not be directly affected.
Relationship between leaf water spin‐lattice relaxation time and water relation parameters in three wheat cultivars
Authors: NAGARAJAN S. , CHAHAL S. S. , GAMBHIR P. N. , TIWARI P. N. 
Published: April 2006

ABSTRACTPot culture studies were conducted using two drought‐tolerant and one susceptible cultivar of wheat (Triticum aestivum L.) under three different moisture regimes. Proton spin‐lattice relaxation time, T1, leaf water content, LWC, leaf water potential, Ψ, solute potential, Ψs and turgor potential, Ψp were measured from 45 to 75 d after sowing at weekly intervals. The three cultivars did not differ significantly in their values of LWC, leaf water potential, and their components in the stressed and unstressed plants; but they did differ significantly in their T1 values both under stressed and unstressed conditions on all days of measurement, with the drought tolerant cultivars having a higher T1 compared to the susceptible cultivar. This suggests that leaf water T1 is a better parameter for describing plant water status than the traditional water relation indices. The relation between Ψ and T1 was logarithmic, indicating the similarity between T1 and water activity of the cellular water.