摘要:

ABSTRACTWe investigated the genetic control of cytosolic fructose‐1,6‐bisphosphatase (cytFBPase) activity, and the relationships between sucrose synthesis capacity and photosynthesis, growth, flowering and whole‐plant carbon partitioning inFlaveria linearisLag. F1; F2, and selfed lines generated from plants with low or high cytFBPase activity were used. CytFBPase activity was controlled by one gene and inherited co‐dominantly, giving three classes of activity (low, intermediate and high). Reversed O2sensitivity of photosynthesis, which indicates an end‐product limitation on photosynthesis, was controlled by one gene and co‐segregated with low cytFBPase activity. A low activity of cytFBPase decreased the growth rate. A recessive day‐neutral flowering trait inFlaveria linearisdid not co‐segregate with cytFBPase activity. Plants with low cytFBPase activity had an increased shoot‐to‐root ratio, and flowering caused an additional shift in carbon partitioning to shoots only in plants with low cytFBPase activity. These data indicate that altering sucrose synthesis can affect photosynthesis and plant gro

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00220.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWide variation exists in the growth responses of C3plants to elevated CO2levels. To investigate the role of photosynthetic feedback in this phenomenon, photosynthetic parameters and growth were measured for lines ofFlaveria lineariswith low, intermediate or high cytosolic fructose‐1,6‐bisphosphatase (cytFBPase) activity when grown at either 35 or 65 Pa CO2. The effects of pot size on the responses of these lines to elevated CO2were also examined. Photosynthesis and growth of plants with low cytFBPase activity were less responsive to elevated CO2, and these plants had a reduced maximum potential for photosynthesis and growth. Plants with intermediate cytFBPase activity also showed a lower relative growth enhancement when grown at 65 Pa CO2. There was a significant pot size effect on photosynthesis and growth for line 85‐1 (high cytFBPase). This effect was greatest for line 85‐1 when grown at 35 Pa CO2, since these plants showed the greatest downward acclimation of photosynthesis when grown in small pots. There was a minimal pot size effect for line 84‐9 (low cytFBPase), and this could be partly attributed to the reduced CO2sensitivity of this line. It is proposed that the capacity for sucrose synthesis in C3, plants is partly responsible for their wide variation in CO2respo

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00221.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTIn order to identify physiological components that contribute to salinity tolerance, we compared the effects of Na+, Mg2+and K+salts (NaCl, Na2SO4, MgCl2, MgSO4, KCl and K2SO4), Ca2+(CaSO4), mannitol and melibiose on the wild type and the single‐gene NaCl‐tolerant mutantsstl1andstl2 of Ceratopteris richardii. Compared with gametophytic growth of the wild type,stl2showed a low level of tolerance that was restricted to Na+salts and osmotic stress.stl2exhibited high tolerance to both Na+and Mg2+salts, as well as to osmotic stress. In response to short‐term exposure (3 d) to NaCl, accumulation of K+and Na+was similar in the wild type andstl1. In contrast,stl2accumulated higher levels of K+and lower levels of Na+. Ca2+supplementation (1.0 mol m−3) ameliorated growth inhibition by Na+and Mg2+stress in wild type and stll, but not instl2. In addition, under Na+stress (175 mol m−3) wild‐type, stll andstl2gametopbytes maintained higher tissue levels of K+and lower levels of Na+when supplemented with Ca2+(1.0 mol m−3).stl2gametophytes were extremely sensitive to K+supplementation. Growth ofstl2was greater than or equal to that of the wild type at trace concentrations of K+but decreased substantially with increasing K+concentration. Supplementation with K+from 0 to 1.85 mol m−3alleviated some of the inhibition by 75 mol m−3NaCl in the wild type and instl1. Instl2, growth at 75 mol m−3NaCl was similar at 0 and 1.85 mol m−3K+supplementation. Although K+supplementation above 1.85 mol m−3did not alleviate inhibition of growth by Na+in any genotype,stl2maintained greater relative tolerance to NaCl at all

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00222.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe roles of K+uptake and loss in the salinity response of the wild type and the salt‐tolerant mutantstl2ofCeratopteris richardiiwere studied by measuring Rb+influx and loss and the effects of Na+, Mg2+, Ca2+and K+‐transport inhibitors. In addition, electrophysiological responses were measured for both K+and Rb+and for the effects of Na+and NH4+on subsequent K+‐induced depolarizations.stl2had a 26–40% higher uptake rate for Rb+than the wild type at 0.5–10 mol m−3RbCl. Similarly, membrane depolarizations induced by both RbCl and KCl were consistently greater instl2. In the presence of 0–180 mol m−3NaCl,stl2maintained a consistently greater Rb+influx than the wild type.stl2retained a greater capacity for subsequent KCl‐induced depolarization following exposure to NaCl. Five mol m−3Mg2+decreased Rb+uptake instl2; however, additional Mg2+up to 40 mol m−3did not affect Rb+uptake further. Ca2+supplementation resulted in a very minor decrease of Rb+uptake that was similar in the two genotypes. Tetraethylammonium chloride and CsCl gave similar inhibition of Rb+uptake in both genotypes, but NH4Cl gave substantially greater inhibition in the wild type than instl2. NH4Cl resulted in a greater membrane depolarization in the wild type and the capacity for subsequent depolarization by KCl was markedly reduced.stl2exhibited a higher Independent loss of Rb+than the wild type, but, in the absence of external K+, loss of Rb+was equivalent in the two genotypes. Since constitutive K+contents are nearly identical, we conclude that high K+influx and loss exact a metabolic cost that is reflected in the inhibition of gametophytic growth. Growth inhibition can be alleviated by reduced supplemental K+or by treatments that slightly reduce K+influx, such as moderate concentrations of Na+or Mg2+. We propose that high throughput of K+allows maintenance of cytosolic K+under salt stress and that a high uptake rate for K+results in a reduced capacity for the entrance and accumulation of alternative cations such

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00223.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTMulti‐proton spin‐echo images were collected from cold‐acclimated winter wheat crowns (Triticum aestivumL.) cv. Cappelle Desprez at 400 MHz between 4 and −4 °C. Water proton relaxation by the spin‐spin (T2) mechanism from individual voxels in image slices was found to be mono‐exponential. The temperature dependence of these relaxation rates was found to obey Arrhenius or absolute rate theory expressions relating temperature, activation energies and relaxation rates, Images whose contrast is proportional to the Arrhenius activation energy (Ea), Gibb's free energy of activation (ΔG‡), and the entropy of activation (ΔS‡) for water relaxation on a voxel basis were constructed by post‐image processing. These new images exhibit contrast based on activation energies rather than rules of proton relaxation. The temperature dependence of water protonT2relaxation rates permits prediction of changes in the physical state of water in this tissue over modest temperature ranges. A simple model is proposed to predict the freezing temperature kof various tissue in wheat crowns. The averageEaand ΔH‡for water protonT2relaxation over the above temperature range in winter wheat tissue were −6.4 ± 14.8 and −8.6 ± 14.8kj mol−1, respectively. This barrier is considerably lower than theEafor proton translation in ice at 0°C, which is reported to

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00224.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAs reported in a previous paper [Lerchlet al. (1995)Plant Cell, 7, 259–270], expression ofEscherichia coliinorganic pyrophosphatase in the cytosol under the control of the phloem‐specificrolC promoter from,Agobacterium rhizogenesresults in decreased growth of transgenic tobacco plants. In this paper we investigate the effect of the phloem‐specific expression of pyrophosphatase on phloem metabolism, and on plant growth and allocation. A small decrease in the hexose phosphate/UDP‐glucose ratio, the ATP/ADP ratio and the respiration rate in the midribs of the transformants provides evidence Hint mobilization of sucrose via pyrophosphate‐dependent reactions is necessary for phloem energy metabolism. The source leaves of the transformants had higher levels of carbohydrates and amino acids and a much higher glutamine/glutamate ratio than the wild type, showing that export was inhibited and that the growth inhibition was not due to a lack of photoas‐similates or organic nitrogen in the leaves. The accumulation of photoassimilates was paralleled by a decrease in photosynthesis, chlorophyll content and ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity, a small increase in hexose phosphates and triose phosphates and a decrease in glycerate 3‐phosphate in the source leaves. There was a decrease of soluble sugars and amino acids in sink leaves of the transformants. In sink leaves amino acids decreased more than carbohydrates and a decrease in the glutamine/ glutamate ratio was observed. This was accompanied by a large decrease of nitrate. Sugars and amino acids were also reduced in the root tips of the transformants. The carbohydrate /amino acid ratio decreased 5‐fold in the root tips, indicating a particularly smile shortage of carbohydrates. Relatively high levels of sugars and amino acids in the basal regions of the root and the increase in sugars in the midrib indicate that there is also increased leakage of assimilates out of the phloem during long‐distance transport. Metabolism is required to maintain phloem function along the transport route, as well as for the initial step of loading. The transformants showed decreased stem and root growth. The growth inhibition was largest in conditions allowing rapid growth of the wild type (high light and

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00225.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe growth pattern of the root system of young rubber trees (Hevea brasiliensis) was studied in relation to shoot development over a period of 3 months. Temporal and spatial variations in elongation and branching processes were examined for the different root types, by means of root observation boxes. Shoot growth was typically rhythmic. Root development was periodic and related to leaf expansion. Root elongation was depressed during leaf growth, whereas branching was enhanced. Consequently, highly branched areas with vigorous secondary roots alternated along the taproot with poorly branched areas with shorter roots. Root types were not affected to the same degree by shoot competition: during leaf expansion, taproot growth was just depressed but remained continuous, the emergence and elongation rates of secondary roots were significantly affected and the elongation rates of tertiary roots fell to zero. These results were consistent with the hypothesis that root growth is related to competition for assimilates and to the sink strength of the different root types, whereas root branching appeared to be promoted by leaf development.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00226.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTPhysiological and biochemical changes related to methyl jasmonate (MeJA)‐induced chilling tolerance of rice (Oryza sativaL. cv. Taichung Native 1) seedlings were investigated. Treatment of whole plants with 10 mmol m−3MeJA for 48 h before chilling (5 °C) was optimal for the induction of chilling tolerance. MeJA greatly improved the survival ratio of chilled seedlings and ameliorated chilling injury such as demolition of membrane structure (estimated by electrolyte leakage). MeJA also prevented water loss in chilled seedlings by reducing the opening of stomata and decreasing the root bleeding rate. Putrescine and spermine levels in shoots increased but spermidine levels decreased on exposure to MeJA. In roots, putrescine levels also increased and spermidine levels increased transiently on exposure to MeJA. Activities of arginine decarboxylase (ADC; EC 4.1.1.19) and S‐adenosylmethionine decarboxylase (SAMDC; EC 4.1.1.50) in both shoots and roots increased on exposure to MeJA, while the activity of ornithine decarboxylase (ODC; EC 4.1.1.17) remained unchanged. The MeJA‐induced putrescine increase was inhibited by 50 mmol m−3α‐difluoromethylarginine (DFMA), an irreversible inhibitor of ADC, but not by 50 mmol m−3α‐difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. The effect of MeJA on the induction of chilling tolerance was also reduced by 50 mmol m−3DFMA. The effects of DFMA were partly prevented by 1 mol m−3putrescine. This indicates that putrescine accumulation is required for the induction of chilling tolerance of

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe stomatal conductance of several anisohydric plant species, including field‐grown sunflower, frequently correlates with leaf water potential (φ1), suggesting that chemical messages travelling from roots to shoots may not play an important role in stomatal control. We have performed a series of experiments in which evaporative demand, soil water status and ABA origin (endogenous or artificial) were varied in order to analyse stomatal control. Sunflower plants were subjected to a range of soil water potentials under contrasting air vapour pressure deficits (VPD, from 0.5 to 2.5 kPa) in the field, in the glasshouse or in a humid chamber. Sunflower plants were also fed through the xylem with varying concentrations of artificial ABA, in the glasshouse and in the field. Finally, detached leaves were fed directly with varying concentrations of ABA under three contrasting VPDs. A unique relationship between stomatal conductance (gs) and the concentration of ABA in the xylem sap (xylem [ABA]) was observed in all cases. In contrast, the relationship between φ1and gsvaried substantially among experiments. Its slope was positive for droughted plants and negative for ABA‐fed whole plants or detached leaves, and also varied appreciably with air VPD. All observed relationships could be modelled on the basis of the assumption that φ1had no controlling effect on gs. We conclude that stomatal control depended only on the concentration of ABA in the xylem sap, and that φ1was controlled by water flux through the plant (itself controlled by stomatal conductance). The possibility is also raised that differences in stomatal ‘strategy’ between isohydric plants (such as maize, where daytime φ1does not vary appreciably with soil water status) and anisohydric plants (such as sunflower) may be accounted for by the degree of influence of φ1on stomatal control, for a given level of xylem [ABA]. We propose that statistical relationships between φ1and gsare only observed when φ1has no controlling action on sto

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe performance of the photosynthetic apparatus was examined in the third leaves ofZea maysL. seedlings grown at near‐optimal (25 °C) or at suboptimal (15 °C) temperature by measuring chlorophyll (ChI)afluorescence parameters and oxygen evolution in different temperature and light conditions. In leaf tissue grown at 25 and 15 °C, the quantum yield of PSII electron transport (ψPSII) and the rate of O2evolution decreased with decreasing temperature (from 25 to 4 °C) at a photon flux density of 125 μmol m−2s−1. In leaves grown at 25 °C, the decrease of ψPSIIcorrelated with a decrease of photochemical ChI fluorescence quenching (qp), whereas in leaves crown at 15 °Cqpwas largely insensitive to the temperature decrease. Compared with leaves grown at 25 °C, leaves grown at 15 °C were also able to maintain a higher fraction of oxidized to reducedQA(greaterqp) at high photon flux densities (up to 2000 μmol m−2s−1), particularly when the measurements were performed at high temperature (25 °C). With decreasing temperature and/or increasing light intensity, leaves grown at 15 °C exhibited a substantial quenching of the dark level of fluorescenceF0(q0) whereas this type of quenching was virtually absent in leaves grown at 25 °C. Furthermore, leaves grown at 15 °C were able to recover faster from photo inhibition of photosynthesis after a photoinhibitory treatment (1200 μmol m−2s−1at 25, 15 or 6 °C for 8 h) than leaves grown at 25 °C. The results suggest that, in spite of having a low photosynthetic capacity,Z. maysleaves grown at sub optimal temperature possess efficient mechanisms of energy dissipation which enable them to cope better with photoinhibition than leaves grown at near‐optimal temperature. It is suggested that the resistance ofZ. maysleaves grown at 15 °C to photoinhibition is related to the higher content of carotenoids of the xanthophyll cycle (violaxanthin + antheraxanthin + zeaxanthin) measured in these l

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00229.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY