摘要:

AbstractStomatal sensitivities to light and VPD have potential as quantitative selection criteria in programs designed to enhance water‐use efficiency of sugarcane and other crops. These responses were characterized using gas exchange techniques and then simulated by a mathematical relationship describing conductance as a function of photon fluence rates and VPD values. The same form of relationship simulated stomatal responses of well‐watered greenhouse‐ and field‐grown plants. A comparison between simulated and measured conductance values showed a close correlation, indicating that light and VPD responses of stomata are dominant input signals modulating stomatal conductance in sugarcane. Observed conductance of Hawaiian sugarcane in a commerical production area appeared larger than required to support prevailing rates of carbon assimilation, since predicted intercellular CO2was greater than required to saturate its C4photosynthesis. Manipulation of the relationship describing stomatal conductance allowed us to simulate the responses of plants with hypothetically altered stomatal sensitivities to VPD or to light, using micrometeorological data collected in the field. Further simulation indicated that selection for clones with altered stomatal sensitivity to either light or VPD could improve the water‐use efficiency of sugarcane without inhibiting current high levels of pro

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602231

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractSalt‐tolerant grasses and a sedge were grown at three salinities in a controlled‐environment greenhouse. They were measured for growth rate, ash content, water content and cations. Fourteen species from the generaSporobolus, Aeluropus, Leptochloa, Paspalum, Puccinellia, Hordeum, Elymus, DistichlisandSpartinasurvived up to the highest salt treatment (540 mol m−3NaCl). These were designated halophytes. Eleven species from the generaTriticum, Phragmites, Dactylotenium, Cynodon, Polypogon, Panicum, JoveaandHeleocharisonly survived up to 180 mol m−3NaCl and were designated salt‐tolerant glycophytes. All species exceptDistichlis palmerigrew fastest on the non‐saline control treatment. All species tended to have higher Na+contents and lower K+and water contents on saline treatments compared to control plants. Halophytes differed from glycophytes in having statistically significant lower water contents on the non‐saline treatment, and lower ash contents and Na:K ratios on 180 mol m−3. However, the range of values among species was greater than the differences between halophytes and glycophytes. All species appeared to use Na+accumulation and loss of water as the main means of osmotic adjustment. Three halophytic species were grown for a longer period of time to check the above results. The osmolality of the cell sap was measured directly by the vapour pressure method and compared to calculated values based on Na+, K+and water contents (and assuming a balancing anion such as Cl−). Na+and K+alone could account for greater than 75% of the osmotic potential at all salinities. Hence, the accumulation of organic solutes did not appear to be an important factor in the osmotic adjustment of these species. The results support the conclusion that grasses coordinate Na+uptake and water loss to maintain a constant osmotic potential gradient between the shoot tissues and the external solution. The results were compared to a previous study with dicotyledonous halophytes at

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602236

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractFlax plants were transferred from 30°C to 15°C temperatures, and then back to 30°C during their vegetative growth phase. Reciprocal transfers were also made from 15°C to 30°C, and then back to 15°C for an identical period at the same time. Plants were also retained in a constant 30°C or 15°C in growth chambers with identical lighting conditions. The reciprocal transfer period lasted 6 d. The relative mobility (Rm) of an anionic leaf peroxidase isozyme, reflecting its molecular weight/conformation and/or net charge, was monitored over a period starting before the reciprocal transfers and finishing after the return to original temperatures. Two of the four flax types which were studied showed isozyme relative mobility responses related either to the different constant temperatures, or to the transfer from 15°C to 30°C. The responses were not reversible on return to the original lower temperature. Thus, exposure to 30°C, even for a transient 6 d period, produced a one way Rmshift. This suggests a developmental switch‐over in the particular form of peroxidase glycoprotein being synthesized, rather than an adaptive response triggered by external environme

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602241

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe purported blocker of anion transport 4, 4′ di‐isothiocyano‐2‐2′ stilbene disulfonate (DIDS) has been shown to partially inhibit36Cl−influx,36CIO−3influx and35SO2−4influx intoPisum salivumL. cv. Feltham First seedlings. This inhibitory effect could be prevented by pretreatment with the respective unlabelled medium. There was no effect of DIDS on14C methylamine influx. The results are consistent with the hypothesis that the binding of DIDS to the site of anion‐carrier interaction is responsible for its observed inhibitory effects on anion fluxes. The fluorescent properties of DIDS upon binding to membrane proteins was exploited in an attempt to examine the major sites of anion pumping in whole roots. The results show clearly that in the presence of DIDS the epidermal layers became brightly fluorescent, while cortical layers did not fiuoresce.Lycopersicum esculentumcells taken from locular fluid were plasmolysed using sucrose solution, and the patterns of fluorescence in the presence of DIDS showed in an unambiguous way that the fluorescence is associated with cell membranes. The potential usefulness of this technique to probe sites of anion transport in whole plants and tis

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602249

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractFusicoccin (FC)‐stimulated K+(86Rb) uptake and proton extrusion of maize (Zea mays) root apical segments were inhibited by pretreatment of 4‐day‐old seedlings with the herbicide Chlorsulfuron. In the range of Chlorsulfuron concentrations 0.01‐10 mmol m−3, the percentage of inhibition was 15% at 0.01 mmol m−3and progressively increased with Chlorsulfuron concentration up to 60% at 10 mmol m−3. At the maximum concentration tested (10 mmol m−3), the inhibition was evident after 1.5 h of pre‐treatment. The binding of FC to microsomal fractions of root segments from Chlorsulfuron‐pretreated seedlings was inhibited by 30%. It is suggested that Chlorsulfuron causes an alteration at the plasmalemma level involving the FC binding sites. The ineffectiveness of Chlorsulfuron in inhibiting FC‐stimulaled K+uptake when administered to excised segments, while inhibiting the enzyme acetolactate synthase, pointed out by Ray (1984) as the site of action of Chlorsulfuron in pea plants, suggests that the observed inhibition of K+uptake and H+extrusion is not induced by Chlorsulfuron inhibition of this enzyme. An alternative site of action of Chlorsulfuron is hypothe

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602255

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractIn a previous study, it was shown that the fungal toxin fusicoccin (FC) is able to stimulate thein vivophosphorylation of a 33 KDalton polypeptide (33 KP) independently of protein synthesis. Here we show that the stimulation by FC of both proton efflux and 33 KP phosphorylation are strongly enhanced when the external medium contains K+or Na+, suggesting that the two phenomena are related. The stimulatory effect of FC is higher in unbuffered than in buffered media; moreover, in the absence of FC, 33 KP is more phosphorylated at an acidic than at a basic pH of the medium, suggesting that the effect of FC may depend, to a certain extent, on the acidification of the free space caused by FC‐promoted proton efflux.Treatments reported to alter the intracellular pH influence 33 KP phosphorylation even more strongly than the external pH does. The acidifying agents isobutyric acid and trimethylacetic acid decrease 33 KP phosphorylation, while the alkalinizing agents, ammonia and procaine, increase it. FC partially counteracts the inhibition by the weak acids, whereas the stimulatory effect of FC is not additive with that of the weak bases.The results indicate that 33 KP phosphorylation senses both the external and internal pH. The stimulatory effect of cytoplasm‐alkalinizing treatments, which mimics that of FC, agrees with the reported capacity of FC to cause cytoplasmic alkalinization, following activation of the plasmalemma proton p

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602262

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe leaves of olive are long lived and likely to experience both chilling and high temperature stress during their life. Changes in photosynthetic CO2assimilation resulting from chilling and high temperature stress, in both dim and high light, are investigated. The quantum yield (φ) of photosynthesis at limiting light levels was reduced following chilling (at 5°C for 12 h), in dim light by approximately 10%, and in high light by 75%; the difference being attributed to photoinhibition. Similar reductions were observed in the light‐saturated rate of CO2uptake (Amax). Decrease inAmaxcorrelated with a halving of the leaf internal CO2concentration (ci), suggesting an increased limitation by stomata following photoinhibition. Leaves were apparently more susceptible to photoinhibitory damage if the whole plant, rather than the leaf alone, was chilled. On return to 26 °C, I he photosynthetic capacity recovered to pre‐stress levels within a few hours if leaves had been chilled in high light for 8 h or less, but did not fully recover from longer periods of chilling when loss of chlorophyll occurred. Leaves which were recovering from chilling in high light showed far more damage on being chilled a second time in high light. Three hours in high light at 38 °C reduced φ by 80%, but φ recovered within 4h of return to 26 °C. Although leaves of Olive are apparently less susceptible to photoinhibitory damage during chilling stress than the short‐lived leaves of chilling‐sensitive annual? crops, the results nevertheless show that photoinhibition during temperature stress is potentially a major factor influencing the photosynthetic productivity of Oliv

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602267

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractCells ofN. bacillarishave been selected that are resistant to the toxic proline analogue azetidine‐2‐carboxylic acid (A2C) in 7% artificial seawater (ASW). This phenotype is stable in the absence of selection pressure. A2C resistance at low salinity was demonstrated to be due to an overproduction of proline in these cells, while levels of other amino acids were unaffected. Both wild‐type and A2C‐resistant cells respond to growth in high salinity media (100% ASW, 200% ASW) by accumulation of proline, but proline levels at all salinities are higher in the A2C‐resistant cells than in the wild‐type. Proline overproduction in the A2C‐resislant cells did not affect fluctuations in the levels of other salinity‐dependent solutes, such as homarine. A mutant with this level of specificity over a wide range of water potentials has not been reported for other plants and algae. Both the wild‐type and A2C‐resistant cells were able to grow over the entire salinity range tested (7%‐300% ASW). However, the A2C‐resistant cells showed a lower division rate than the wild‐type in 300% ASW, and yield of A2C‐resislant cells was lower than yield of wild‐type cells at the salinity extremes (7% ASW, 300% ASW). The response or wild‐type and A2C‐resistant cells to rapid increases in salinity were similar for both growth and photosynthesis. The presence of a constitutive high level of proline in the A2C‐resistant cell line did not confer any obvious increased tolerance to salinity shocks, indicating that there are other important factors in the biochemical ad

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602272

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractDuring incubation of maize scutellum slices in fructose, there was an efflux of sucrose. Efflux was constant for at least 4 h at fructose concentrations of 70 or 100 mol m−3. Efflux was increased by EDTA, and decreased by Ca2+. Efflux was independent of pH after EDTA treatment, but increased from untreated slices when the pH was lowered from 7 to 4. Uranyl ion and PCMBS (p‐chloro‐mercuribenzenesulfonic acid) abolished sucrose uptake, but were only weak inhibitors of sucrose efflux. These results are consistent with efflux occurring by simple diffusion through aqueous pores, but they do not rule out facilitated diffusion. Rates of sucrose export from the scutellum to the root shoot axis were estimated from measurements of axis respiration and dry weight gain. Sucrose efflux from scutellum slices was only 14‐22% of the export rate. Sucrose efflux from the whole scutellum was only 3‐4% of the export rate. It is concluded that the observed efflux is from leaky cells and does not represent sucrose on the way to the phloem along a path that includes the apoplast. These results support the idea that the path for sucrose from parenchyma cell to sieve tube in the maize scutellum is entirely s

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602277

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractIncreasing atmospheric CO2may result in alleviation of salinity stress in salt‐sensitive plants. In order to assess the effect of enriched CO2on salinity stress inAndropogon glomeratus, a C4non‐halophyte found in the higher regions of salt marshes, plants were grown at 350, 500, and 650 cm3m−3CO2with 0 or 100 mol m−3NaCl watering treatments. Increases in leaf area and biomass with increasing CO2were measured in salt‐stressed plants, while decreases in these same parameters were measured in non‐salt‐stressed plants. Tillering increased substantially with increasing CO2in salt‐stressed plants, resulting in the increased biomass. Six weeks following initiation of treatments, there was no difference in photosynthesis on a leaf area basis with increasing CO2in salt‐stressed plants, although short‐term increases probably occurred. Stomatal conductance decreased with increasing CO2in salt‐stressed plants, resulting in higher water‐use efficiency, and may have improved the diurnal water status of the plants. Concentrations of Na+and Cl−were higher in salt stressed‐plants while the converse was found for K+. There were no differences in leaf ion content between CO2treatments in the salt‐stressed plants. Decreases in photosynthesis in salt‐stressed plants occurred primarily as a result of decreased inte

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11602285

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY