共查询到20条相似文献,搜索用时 31 毫秒
1.
A karyopherin (LeKAP1) cDNA was isolated from tomato
plants. The deduced LeKAP1 protein sequence of 527 amino acids
showed similarity to other plant karyopherin proteins. When
LeKAP1 was expressed in a yeast two-hybrid
system together with the gene coding for the capsid protein (CP) of the
tomato yellow curl leaf virus (TYLCV), it interacted directly with CP.
Thus, LeKAP1 may be involved in the nuclear import of TYLCV CP
and, potentially, the TYLCV genomes during viral infection of the host
tomato cells. 相似文献
2.
In a companion paper several methods of calculating the marginal unit water
cost of plant carbon gain (E/A) were tested to determine
whether stomata were behaving optimally in relation to regulating leaf gas
exchange. In this paper one method is applied to several tropical tree
species when leaf-to-air vapour pressure difference (D), photosynthetic
photon flux density, leaf temperature, and atmospheric soil water
availability were manipulated. The response of leaves that had expanded
during the dry season were also compared to that of leaves that had
expanded in the wet season. Few differences in absolute value of
E/A, or the form of the relationship, were observed
between species or between seasons. In the majority of species,
E/A increased significantly as either leaf-to-air vapour
pressure difference increased, at a leaf temperature of either 33C or 38C, or as in
photosynthetic photon flux density increased. In contrast, as leaf
temperature increased at constant D, E/A was generally
constant. As pre-dawn water potential declined, E/A
declined. The relationship between E/A and D did not
differ whether internal or ambient carbon dioxide concentration were kept
constant. It is concluded that stomata are only behaving optimally over a
very small range of D. If a larger range of D is used, to incorporate
values that more closely reflect those experienced by tropical trees in a
savanna environment optimization is incomplete.Key
words: Stomatal optimization theory, marginal unit water cost.
相似文献
3.
The role of solute accumulation, osmotic adjustment and changes in cell wall elasticity in drought tolerance in Ziziphus mauritiana (Lamk.) 总被引:3,自引:0,他引:3
Clifford S; Arndt S; Corlett J; Joshi S; Sankhla N; Popp M; Jones H 《Journal of experimental botany》1998,49(323):967-977
Ber (Ziziphus mauritiana Lamk.) is a major fruit tree
crop of the north-west Indian arid zone. In a study of the physiological
basis of drought tolerance in this species, two glasshouse experiments were
conducted in which trees were droughted during single stress-cycles. In the
first experiment, during a 13 d drying cycle, pre-dawn leaf water
(leaf) and osmotic () potentials in droughted
trees declined from -0.5 and -1.4 MPa to -1.7 and -2.2 MPa, respectively,
for a decrease in relative water content () of 14%. During
drought stress, changes in sugar metabolism were associated with
significant increases in concentrations of hexose sugars (3.8-fold),
cyclitol (scyllo-inositol; 1.5-fold), and proline (35-fold; expressed per
unit dry weight), suggesting that altered solute partitioning may be an
important factor in drought tolerance of Ziziphus. On
rewatering pre-dawn leaf and recovered fully, but
remained depressed by 0.4 MPa relative to control
values, indicating that solute concentration per unit water content had
changed during the drought cycle.Evidence for osmotic adjustment was
provided from a second study during which a gradual drought was imposed.
Pressure-volume analysis revealed a 0.7 MPa reduction in osmotic potential
at full turgor, with leaf at turgor loss depressed by 1 MPa in
drought-stressed leaves. Coupled with osmotic adjustment, during gradual
drought, was a 65% increase in bulk tissue elastic modulus (wall rigidity)
which resulted in turgor loss at the same in both stressed and
unstressed leaves. The possible ecological significance of maintenance of
turgor potential and cell volume at low water potentials for drought
tolerance in Ziziphus is discussed.Keywords:
Ziziphus mauritiana, drought, solute
accumulation, osmotic adjustment, proline.
相似文献
4.
Short communication. A steep Ca2[IMAGE]-dependence of a K[IMAGE] channel in a unicellular green alga
Bauer C; Plieth C; Hansen U; Simonis W; Schonknecht G 《Journal of experimental botany》1998,49(327):1761-1765
An increase of cytosolic Ca2 in the
unicellular green alga Eremosphaera viridis activities
Ca2-dependent
K channels causing a hyperpolarization of
the plasma membrane. Data from parallel calcium, and potential measurements
were combined with I/V relationships. This yielded a
steep Ca2-dependence of
K channels with a co-operativity of 4 and
an affinity of 300 nM.Key words: Eremosphaera viridis,
plasma membrane, Ca2-dependent
K channel, co-operative binding.
相似文献
5.
In recent years alternative ways have been proposed to transformmeasurements of leaf water potential, , and relative water content,R*, in order to derive values of osmotic pressure at full turgidityin leaves and shoots, o(when 0). Two types of transformationsare usually considered: 1/ versus R* and versus 1/R*, and linearregression is used to fit the data in the region where turgoris thought to be zero. It appears that when o is estimated bylinear extrapolation of 1/Psi; versus R* then apoplastic watermight not influence the accuracy of o but when the versus \/R*transformation is used apoplastic water causes an underestimateof o. We examine the accuracy of the estimate of o obtainedfrom the two transformations when there are random errors in, systematic errors in , and when the osmotic solutions arenon-ideal. The 1/ versus R* transformation generally producesthe best estimate of 0 by linear extrapolation. 相似文献
6.
The objective was to determine whether the protein of
rolB affects shoot formation and whether this
potential relationship depends on the developmental stages of the plant
and/or on the culture conditions. Thin cell layers (TCL) and leaf explants
were excised from tobacco plants in the vegetative and flowering stages and
cultured under various hormonal conditions. In TCLs of vegetative-stage
plants, the expression of rolB enhanced the formation
of the shoot buds under hormone-free conditions and with specific
concentrations of auxin and/or cytokinin. Histological examination showed
that the induction of the shoot meristemoids was particularly enhanced by
rolB protein and that meristemoid growth was
accelerated. In leaf explants from vegetative-stage plants, the expression
of rolB increased the formation of shoot buds in the
presence of 1 M IAA plus 1 or 10 M cytokinin. With BA alone, at a 0.1 M concentration, shoot formation occurred in the
transgenic explants only, whereas with concentrations ranging from 0.5 to
10 M, it was higher in these explants than in
controls.RolB protein enhanced the formation of shoot
buds in TCLs from flowering plants under all hormonal conditions. In the
presence of 1 M IAA and kinetin, the protein also increased the
flowering response. In leaf explants from flowering plants, the expression
of rolB increased the number of shoot buds in the
presence of 1 M IAA with 10 M BA.In conclusion,
rolB protein promotes shoot formation; it seems to
have a positive interaction with cytokinin and an effect on the induction
of the meristematic condition. 相似文献
7.
An equation is derived expressing average turgor pressure ofa leaf (p) as a function of relative water content (RWC). Basedon this derivation, the relationships of the bulk elastic modulus(v) and both RWC and p, are formulated and discussed. The bulkelastic modulus (v) becomes zero for p = 0, that is at the turgorloss point for the leaf. At full water saturation the valueof ev is proportional to the water saturation turgor potentialp(max). The factor relating P and v (structure coefficient ,Burstrom, Uhrstr?m and Olausson, 1970) changes only very littlefor values of p, which are not too close to zero. An exampleis given for the calculation from experimental data of the turgorpressure function, the structure coefficient function, and thev function. Key words: Cell wall, Turgor pressure, Bulk elastic modulus 相似文献
8.
Mastoparan analogues stimulate phospholipase C- and phospholipase D-activity in Chlamydomonas: a comparative study 总被引:1,自引:0,他引:1
van Himbergen J; ter Riet B; Meijer H; van den Ende H; Musgrave A; Munnik T 《Journal of experimental botany》1999,50(341):1735-1742
The G-protein activator mastoparan and its analogues are becoming popular
tools for studying signalling in plants. Therefore the abilities of
mastoparan, mas7, mas8, and mas17 to activate phospholipase C (PLC), PLD
and to induce the deflagellation response in Chlamydomonas
moewusii Gerloff were compared. The aim was to test whether
their relative potencies in a plant system resemble those reported for
bovine brain Go and Gi, as is generally assumed, and to determine at which
concentrations cells become permeabilized, a known effect of higher
concentrations. The concentrations at which 50% deflagellation was induced,
were 2.0 M mastoparan, 3.0 M mas8, 3.6 M mas7, and 5.8 M
mas17. Similar activities were found for the production of phosphatidic
acid, which is the result of the combined activities of PLD and PLC
(together with diacylglycerol kinase). PLD activity alone was measured
in vivo by its ability to phosphatidylate
n-butanol. Surprisingly, the concentrations that
stimulated maximum activity were about 10-fold lower (1
M) than those that stimulated maximum PLC activity (10
M). Mas17 was an exception with both maxima above 10 M.
All the compounds except mas17 permeabilized C.
moewusii cells. The concentrations at which 50% of the cells
were permeabilized to Evan's blue were 7.4 M mas8, 16.0 M
mas7 and 22.4 M mastoparan. In conclusion, only mastoparan itself
and the least active analogue mas17 induced maximum deflagellation, PLC and
PLD activities without permeabilizing the cells.Keywords:
Chlamydomonas, deflagellation, mastoparan,
phospholipases C and D, phospholipid metabolism
相似文献
9.
Changes in components of leaf water potential during soil waterdeficits influence many physiological processes. Research resultsfocusing on these changes during desiccation of peanut (Arachishypogeae L.) leaves are apparently not available. The presentstudy was conducted to examine the relationships of leaf waterl, solute s and turgor p potentials, and percent relative watercontent (RWC) of peanut leaves during desiccation of detachedleaves and also during naturally occurring soil moisture deficitsin the field. The relationship of p to l and RWC was evaluated by calculatingp from differences in l and s determined by thermocouple psychrometryand by constructing pressure-volume (P-V) curves from the land RWC measurements. Turgor potentials of Early Bunchand Florunner leaves decreased to zero at l of1.2 to 1.3 MPa and RWC of 87%. There were no cultivardifferences in the l at which p became zero. P-V curves indicatedthat the error of measuring s after freezing due to dilutionof the cellular constituents was small but resulted in artefactualnegative p values. Random measurements on two dates of l, s, and calculation ofp from well-watered and water-stressed field plots consistingof several genotypes indicated that zero p occurred at l of1.6 MPa. It was concluded that the relationships of p,l, s, and RWC of peanut leaves were similar to leaves of othercrops and that these relationships conferred no unique droughtresistance mechanism to peanut. 相似文献
10.
The Relationship Between Transpiration Rate, Water Potential, and Resistances to Water Movement in Sunflower (Helianthus annuus L.) 总被引:3,自引:0,他引:3
The effects of transpiration rate on the vertical gradientsof leaf and stem xylem water potential ( and ) were examinedusing hydroponic sunflower plants. Transpiration was variedby stepwise alterations of environmental conditions. The gradientsof and were relatively small (2.3 and 0.8 x 105 Pa m1)when transpiration rates approached zero, but increased sharplyto 5.4 and 2.3 x 105 Pa m1 as transpiration increased.However, the gradients were independent of transpiration ratesabove 0.4 g dm2 h1 owing to variability of theplant resistance. The gradients of I were usually less thanhalf those of I. 1 in individual leaves remained constant over a wide range oftranspiration rates (0.42.4 g dm2 h1) andeach leaf possessed a characteristic plateau value related toits elevation. I responded similarly but was approximately 2.0x 105 Pa higher than I at the same elevation. Identical resultswere obtained regardless of the procedure employed to vary transpiration. The drop in water potential between stem and leaf implies thatthe leaf resistance is appreciable. This was confirmed usingrapidly transpiring excised leaves freely supplied with water.I increased by 2.02.5 x 105 Pa following removal of theroot resistance but remained 2 x 105 Pa lower than similar excisedleaves in darkness. Furthermore, I in excised leaves remainedconstant over a wide range of transporting rates, demonstratingthat the leaf resistance is also variable. The results are discussed in relation to previous reports. 相似文献
11.
Derivation of Pressure-Volume Curves by a Non-Linear Regression Procedure and Determination of Apoplastic Water 总被引:1,自引:0,他引:1
Data from pressure-volume (PV) analysis may be submitted totransformation I [i.e. leaf water potential (1) versus inverserelative water content (1/R)] or to transformation II (i.e.1/1 versus R). This may cause an essential distortion of theerror structure especially in transformation II due to the relativelylarge range which is to be covered by the 1/1 ratio. Similarly,logarithmic transformation of leaf turgor potential (P) whenderiving the sensitivity factor of elasticity (ß)by linear regression from values of In p and 1/R may distortthe error structure. In order to investigate the magnitude ofthe distortion effect on parameters derived from PV analysisby regression a non-linear regression procedure was comparedwith the common linear procedure when calculating p from ßin the turgid region and leaf osmotic potential (P) in boththe turgid and non-turgid region. As test plants we used fieldgrown species of spring barley (Hordeum distichum L., cvs Gunnarand Alis). The results show that transformations and applicationof linear regression procedures distort the error structureof p more than the error structure of ', which was only slightlyaffected. However, we recommend the use of the non-linear procedurein both cases. Furthermore, from PV analysis, obtained by thermocouple hygrometryon living and killed leaf tissue, respectively, we derived themathematical basis for calculating the apoplastic water fraction(Ra). Ra was 0.15 at R= 1 and decreased with dehydration. The equations describing the relation between and R and betweenp and R were extended to take into account the apoplastic waterfraction. Key words: Apoplastic water, distortion errors, non-linear regression, pressure-volume curves 相似文献
12.
HENSON I. E.; ALAGARSWAMY G.; MAHALAKSHMI V.; BIDINGER F. R. 《Journal of experimental botany》1983,34(4):442-450
The water potential () at which stomata completed closure (8Lmin)was determined for pearl millet (Pennisetum americanum [L.]Leeke) at two growth stages by monitoring changes in leaf conductance(gL) and following shoot detachment. Leaf water status wasevaluated concurrently using a pressure-volume (P-V) technique. In a pot experiment with young vegetative plants, 8Lmin closelyapproximated to the estimated at zero turgor (u) both for controland for drought-conditioned plants which had osmotically adjusted.However, for penultimate leaves of field-grown flowering plants,8Lmin was found to be 0.61 (irrigated plants) and 0.87 (droughtedplants) MPa below u. In drought-stressed field-grown plants,osmotic adjustment (characterized by a decrease in solute (osmotic)potential (s ) at both full hydration and zero turgor) was insufficientto maintain a positive bulk leaf turgor potential (p) once had declined to below about -1.5 MPa. It is suggested that localizedadjustment by the stomatal complex in response to environmentaldifferences, leaf ageing and/or ontogenetic change, is responsiblefor the uncoupling of stomatal from bulk leaf water status. Key words: Stomata, Water stress, Pennisetum americanum 相似文献
13.
The Meaning of Matric Potential 总被引:6,自引:1,他引:5
The commonly used equation, = P - + , which describes thepartitioning of plant water potential, , into components ofhydrostatic pressure, P, osmotic pressure, , and matric potential,, is misleading. The term , which is supposed to show the influenceof a solid phase on , is zero if a consistent definition ofpressure is used in the standard thermodynamic derivation. However,it can be usefully defined by = + D, where D is the osmoticpressure of the equilibrium dialysate of the system. The practicaland theoretical significance of this definition is discussed. 相似文献
14.
An error occurs in the calibration of xylem pressure potential() against leaf-water potential () when the calibration is madeusing plant material in which the water stress has been inducedartificially after excision. The impostion of water stress afterexcision affects the determination more than it affects , consequentlythe relationship between these two indices of water stress isaltered. Care should be exercised to ensure that identical proceduresare adopted during . calibrations and during susbsequent fieldmeasurements of with the pressure-chamber apparatus. 相似文献
15.
Photorespiratory glycine enhances glutathione accumulation in both the chloroplastic and cytosolic compartments 总被引:7,自引:0,他引:7
Transformed poplars overexpressing -glutamylcysteine synthetase (-ECS) in the chloroplast (Lggs) were used to
investigate chloroplastic biosynthesis of glutathione (GSH). In Lggs
leaves, GSH contents were enhanced by up to 3.7 fold. In general, the
highest GSH contents were observed in lines with highest
-glutamylcysteine (-EC) contents. These lines had
relatively low glycine. In darkness, foliar GSH decreased and -EC
increased. Illumination of pre-darkened Lggs in air resulted in a 5-fold
decrease in the -EC : GSH ratio. This light-induced decrease was
largely abolished if leaves were illuminated at high CO2. Consequently, the
-EC : GSH ratio of illuminated leaves was much higher at high CO2
than in air. At high CO2 total foliar amino acids were
higher, but glycine and serine were lower, than in air. These results
suggest that photorespiratory glycine is used in chloroplastic GSH
synthesis. Despite this net CO2 fixation was similar in Lggs to
untransformed poplars. Pre-illuminated leaf discs from Lggs, and poplars
overexpression -ECS in the cytosol (ggs), were incubated in
darkness with a range of metabolites. After 15 h, discs for both types of
transformant incubated on water had accumulated high levels of -EC
and showed marked increases in the -EC : GSH ratio. Feeding
glycine, serine, glycollate or phosphoserine, attenuated the dark-induced
changes in the -EC : GSH ratio, whereas 3-phosphoglycerate (PGA),
phosphoenolpyruvate, glycerate, and hydroxypyruvate did not. Glycine
produced from glycollate was therefore required for maximal GSH
accumulation in both the chloroplastic and cytosolic compartment.
Production of glycine from PGA failed to meet the demand of increased GSH
synthetic capacity. 相似文献
16.
17.
Phytosulphokine-{alpha}, a peptidyl plant growth factor, stimulates somatic embryogenesis in carrot 总被引:1,自引:0,他引:1
Kobayashi T; Eun C; Hanai H; Matsubayashi Y; Sakagami Y; Kamada H 《Journal of experimental botany》1999,50(336):1123-1128
Phytosulphokine- (PSK-) is the first chemically characterized peptide
that acts as a plant growth factor. It stimulates the proliferation of
asparagus and rice cells, but no information is yet available on its
effects on plant morphogenesis. The effects of PSK- on somatic
embryogenesis in carrot (Daucus carota L.) were
examined. PSK-, when added to the induction medium for somatic
embryogenesis, increased the number of somatic embryos. The chemical
analogues [2-5]PSK- and tyrosine sulphate ester (Tyr-SO3 H), which
have been used as negative controls in other systems, had no effect.
Moreover the proliferation of cells during somatic embryogenesis was also
enhanced by PSK- these results indicate that PSK-
enhanced cell division and, as a consequence, stimulated carrot somatic
embryogenesis. PSK- also stimulated the proliferation of
embryogenic cells in medium that contained 2,4-dichlorophenoxyacetic acid
(2,4-D), in which somatic embryos did not form, as well as the
proliferation of non-embryogenic cells (cells that had lost the ability to
form somatic embryos) in medium without 2,4-D. These results indicate that
PSK- has a stimulatory effect on cell division generally in carrot
cell cultures.Key words: Daucus carota, plant growth
factor, somatic embryogenesis, sulphated peptide.
相似文献
18.
The euryhaline charophyte Lamprothamnium papulosum (Wallr.)J. Gr. was adapted to media with decreasing salinities rangingfrom 550 to 0 mosmol kg1. Vegetative plants grown inmedia with osmotic pressures (0) in the range of 550 to 130mosmol kg1 maintained a constant turgor pressure () at309 + 7 mosmol kg1. The ions K+, Na+ and Cl, werethe predominant solutes in the vacuole. Changes in their concentrationsaccount for the variation in internal osmotic pressure (1) with,0. The divalent ions Mg2+, Ca2+ and were also present in significant amounts, but their concentrationsdid not alter with changes in, 0. In cells subjected to hypo-osmotic shock the regulation of was incomplete. The turgor pressure increased from 302 to 383mosmol kg1. The first rapid response to the sudden decreasein 0 was a loss of K+ and Cl. In contrast to the decreasein ionic concentrations an accumulation of sucrose occurredwhich could account for the increase of . The increase in sucroseconcentration started 24 to 48 h after the downshock and reachedits highest value after 3 to 4 weeks. The sucrose concentrationin the vacuole was up to 320 mol m3. During this timethe ionic content continued to decrease but did not counterbalancethe sucrose concentration sufficiently to regain the original. High sucrose levels accompanied by an enhanced were also observedduring the period of fructification (sexual reproduction: formationof antheridia and oogonia) in Lamprothamnium kept under conditionsof constant salinity. It is concluded that high sucrose content and elevated arecharacteristic of sexual reproduction in this charophyte. Lamprothamniumis able to tolerate different during various developmentalstages (e.g. vegetative and reproductive phases). Key words: Lamprothamnium papulosum, sucrose, turgor pressure 相似文献
19.
Legge, N. J. 1985. Water movement from soil to root investigatedthrough simultaneous measurement of soil and stem water potentialin potted trees.J. exp. Bot. 36: 15831589. Osmotic tensiometers implanted in the stems of three mountainash (Eucalyptus regnans F. Muell.) saplings growing in largeplastic bins recorded stem water potential, w, while soil waterpotential, w, was simultaneously recorded by instruments nearthe trees' roots and in the surrounding root-free soil Earlyin a drying cycle, with the soil still wet, the diurnal variationin 1, was often slight, despite diurnal variations in u approaching2.0 M Pa. Late in a drying cycle the diurnal fluctuations in1, and u were very similar although changes in 1, still laggedup to 1.5 h behind changes in u. 1values at this time occasionallyreached 3.0 MPa with no apparent damage to the treesWatering the bins in daytime led to a response in 1, valueswithin about 5 min, whereas u, values did not respond for afurther 20 min. u values then rose rapidly but after only 1h began to decline again, while 1, values remained at or nearsaturation for the rest of the day. Water uptake hypotheseswhich attribute an important role to a soil-root interface resistanceare not supported by these data Key words: Soil water potential, penrhizal gradients 相似文献
20.
Aspects of the water relations of spring wheat (Triticum aestivumL.) are described for cultivars Highbury (low ABA) and TW269/9(high ABA), and low and high ABA accumulating F6selections derivedfrom a cross between them. In a pot experiment, pressure-volume (P-V) curves were constructedfor main stem leaf four (MSL4) of well-watered plants of Highburyand TW269/9. Estimates of solute potential (2) from these curveswere similar for the two cultivars, but varied with the timeof sampling and the time allowed for hydration in dim light. In a field experiment with four low and four high ABA F6lines,P-V curves for flag leaves from both droughted and irrigatedplants gave at both zero turgor (p) and zero water potential(1) which differed with degree of stress, sampling time andgenotype. 1was strongly dependent on the initialL of the leafand was reduced on average by c. 0.4 MPa per MPa decline ininitial L.5, was lower (more negative) by c. 0.1-MPa in theafternoon than in the morning. Overall, was also 0.1 MPa lowerin low ABA lines than in high ABA lines. In another field experiment, flag leaves of five low and fivehigh ABA F6lines were sampled over a 4 week period from droughtedplots and L and 5, measured (the latter by osmometry with expressedsap). For these leaves 5, at zero p or zero L was consistentlylower by 0.30.5 MPa than estimates of 5, from the P-Vcurves with flag leaves. However, data for the low ABA lineswere again lower (by c. 0.1 MPa) than those for high ABA lines. The consequences of these differences in 1 are discussed inrelation to the stimulation of ABA accumulation in low and highABA selections. Key words: Water potential, Solute potential, P-V curves, Wheat (Triticum aestivum), Drought stress 相似文献