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1.
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.
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2.
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.
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4.
Bromus tectorum L. (cheatgrass) is an invasive winter
annual whose seeds lose dormancy through dry after-ripening. In this paper
a thermal after-ripening time model for simulating seed dormancy loss of
B. tectorum in the field is presented. The model
employs the hydrothermal time parameter mean base water potential
(b(50)) as an index of dormancy status. Other parameters of the
hydrothermal time equation (the hydrothermal time constant HT,
the standard deviation of base water potentials b, and
the base temperature Tb) are held constant, while
b(50) is allowed to vary and accounts for changes in germination
time-course curves due to stage of after-ripening or incubation
temperature. To obtain hydrothermal time parameters for each of four
collections, seeds were stored dry at 20C
for different intervals, then incubated in water (O MPA) or polyethylene
glycol (PEG) solutions (-0.5, -1.0, -1.5 MPa) at 15 and 25C. Germination data for the thermal after-ripening
time model were obtained from seeds stored dry in the laboratory at 10, 15,
20, 30, 40, and 50°C for 0 to 42 weeks, then incubated at two
alternating temperatures in water. Change in b(50) was
characterized for each collection and incubation temperature as a linear
function of thermal time in storage. Measurements of seed zone temperature
at a field site were combined with equations describing changes in
b(50) during after-ripening to make predictions of seed dormancy
loss in the field. Model predictions were compared with values derived from
incubation of seeds retrieved weekly from the field site. Predictions of
changes in b(50) were generally close to observed values,
suggesting the model is useful for simulating seed dormancy loss during
after-ripening in the field. 相似文献
5.
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
6.
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
7.
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
8.
The daily cycle of the transpiration rate, stomatal conductance,water potential, and the concentration of the main osmoticumidentified in ash leaves, malate and mannitol, were monitoredin a field on the Isere river plain. On sunny days, the stomatalconductance tends to remain close to its maximun value allowinga high transpiration rate and diurnal variations in leaf waterpotential, w, which may fall as low as 2 MPa at solarnoon. These variations of w are closely correlated with changesin malate, mannitol and the concentration of the well-knownosmoticum K+, which agree with the involvement of an osmoticadjustment to counteract the evaporative demand during daylighthours. How malate, mannitol and K+ contribute to the osmoticadjustment was analysed subsequently by comparing the solutepotential s, evaluated by the Boyle-Van't Hoff relation, tothe osmotic potential measured by thermocouple psychrometry.These experiments have led us to suspect some errors in themeasurement of , presumably due to experimental artefacts andthe ability of Ca 2+ , present in high levels in leaves, toform chelates with malate once the cells have been decompartmentedby freezing and thawing. Since significant changes of Ca2+ alsooccurred during the diurnal variations of w, the possible mechanismsby which Ca2+ may be implicated in controlling the water statusof the tree are discussed. Key words: Fraxinus excelsior L, osmotic adjustment, thermocouple psychrometry, malate, calcium 相似文献
9.
LOBODA T.; KLECZKOWSKI L. A.; TARLOWSKI J.; NALBORCZYK E. 《Journal of experimental botany》1988,39(12):1765-1770
The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (Pn, the CO2 compensation point (),post-lower illumination burst of CO2 (PLIB) and post-lower temperatureburst of CO2 (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m3),-HPMS initially stimulated Pn and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.055.0 mol m3. The effects of -HPMS onPn and were time-dependent and, after a few minutes, the Pnwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m 3), the transient effects of-HPMS were shorter () or not observed at all (Pn. Both PLIBand PLTB, when expressed in relation to Pn, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate Pn by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO2 compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis 相似文献
10.
The Role of Glutamate Decarboxylase and {gamma}-Aminobutyric Acid in Germinating Barley 总被引:1,自引:0,他引:1
The variations in glutamate decarboxylase activity and in glutamicacid and -ABA concentration have been measured in barley embryosduring the uptake of water and in the roots and shoots for upto 6 days of growth. Glutamate decarboxylase activity was relativelysteady in the embryos during soaking but rose rapidly once growthbegan. This development paralleled an increase in the concentrationof glutamic acid in both roots and shoots at a time when theconcentration of -ABA was falling. During soaking in aeratedwater, the -ABA content of the embryos rose for 36 h, at whichpoint it accounted for 35 per cent of the soluble amino acids.-ABA was found to be a major free amino acid in roots but notin shoots. Experiments in vivo involving 14C-labelled glutamicacid and -ABA indicated that carbon from -ABA passed very rapidlyinto the citric-acid cycle intermediates and also that, throughoutthe period studied, -ABA was formed from glutamic acid despitethe alterations in relative concentrations of these amino acidsin the growing tissue. 相似文献
11.
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
12.
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
13.
Mechanisms of Inhibition of Water Movement in Anaerobically Treated Roots of Zea mays L. 总被引:2,自引:0,他引:2
Changes in water flux (Jv) across detopped, 7-d-old, maize rootswere characterized during the initial 24 h of being made anoxicby exposure to an anaerobic nutrient solution. Suction (50 kPa)was applied to the xylem and samples of the xylem sap were collectedat intervals and the osmolality and ionic content were measured. Values of Jv through anoxic roots fell below those of aerobiccontrols 1 h after the equilibrium oxygen partial pressure inthe bathing medium dropped below 20 kPa (air = 20.6 kPa). Thereduction in Jv was due primarily to a nullification of thediurnal rhythm in hydraulic conductivity (Lp) that was measuredin aerobic roots. However, about one-quarter of the reductionin Jv could be accounted for by a smaller osmotic componentof the driving force () on water movement. The significance of changes in Jv in anoxic roots is discussedin terms of the reliability of estimates of Lp, the reflectioncoefficient () and . Key words: Anaerobiosis, hydraulic conductivity, osmotic potential, water 相似文献
14.
Mycorrhizal influence on hydraulic and hormonal factors implicated in the control of stomatal conductance during drought 总被引:17,自引:1,他引:16
Duan Xiangrong; Neuman Dawn S.; Reiber Janet M.; Green Craig D.; Saxton Arnold M.; Aug Robert M. 《Journal of experimental botany》1996,47(10):1541-1550
During drying, mycorrhizal plants often maintain higher stomatalconductance (gs) than similarly-sized and -nourished non-mycorrhizalplants, but the mechanism of mycorrhizal influence remains unclear.Several hydraulic and non-hydraulic factors previously implicatedin control of stomatal behavior during drought were measured,to learn which are affected when roots of cowpea (Vigna unguiculata[L.] Walp. cv. White Acre) are extensively colonized by Glomusintraradices Schenck and Smith isolate UT143. At low soil watercontents (), mycorrhizal plants maintained higher gs, transpirationand shoot water potential () than non-mycorrhizal plants. Thesehigher foliar water status characters were associated with lowerxylemsap abscisic acid concentrations ([ABA]) and lower ABAfluxes to leaves in mycorrhizal plants at low soil . Stomatalconductance was most closely correlated with xylem-sap [ABA],ABA flux to leaves and shoot . Stomatal conductance was notcorrelated with xylemsap concentrations of calcium or zeatinriboside equivalents, or with xylem-sap pH, nor were these xylem-sapconstituents affected by mycorrhizal symbiosis. Stomata of mycorrhizaland non-mycorhizal leaves showed similar sensitivities to ABA,whether leaves were intact or detached. It is concluded thatmycorrhizal fungi probably increased the capability of rootsystems to scavenge water in drier soil, resulting in less strainto foliage and hence higher gs, and shoot at particular soil. Key words: Abscisic acid, cytokinins, Glomus intraradices 相似文献
15.
An apparatus for determining water potential of leaves () isdescribed. It is a modification of one previously developedby van Andel for determining osmotic potentials of sap (), forwhich purpose it may still be employed. A constantanminalphathermocouple is used for direct determination of wet-bulb temperaturedepression of air in moisture equilibrium with leaves. The system has advantages over others in simplicity of manufactureand electrical circuitry, and in adaptability to a range ofsignal reading and recording methods. It is capable of handlingrelatively large samples, e.g. 20 cereal leaves of total area(single side) of 300 cm2. Tests of leaf maturity and position effects in two potato cropsare described. Differences between corresponding values of and , considered indicative of cell wall pressures, were lessin lower leaves. In one crop, was lower in relation to leafrelative water content with lower than with upper leaves and,in the other crop, with leaves from the more mature stages ofgrowth. These findings are in accord with a higher rigidityof cell walls in lower and more mature leaves. Mean differences of and involved in the above conclusionswere small, usually less than 2 bar, indicating the potentialusefulness of the apparatus. 相似文献
16.
Commonality in diurnal variation in net uptake of by the grasses Phleum pratense L. cv. Bodin (timothy),and Festuca pratensis Huds. cv. Salten (fescue) was evaluatedin flowing solution culture under a semi-natural light regime.Hourly uptake rates from constant 20 mmol m3 concentrationsof each ion were measured concurrently over 7 d, without physicaldisturbance. The light period was 11 h, natural light supplementedby constant artificial illumination, with a step-transitionto a 13 h dark period. Uptake of all three ions showed a broadlysimilar pattern of diurnal variation, rates increasing duringthe light period and decreasing during the darkness to a minimumwithin 2 h of the end of the dark period. The amplitude wasgreatest during high-irradiance days, and both proportionatelyand absolutely greater for (mean min:max uptake?0.24) than (min:max=0.41) or K+ (min:max?0.34). There were significantdifferences between and the other two ions whose behaviour coincided in almost all respects, in timing of maximum and minimumrates, and acceleration in uptake during the light period. Preferentialuptake of over increased sharply during the first half of the lightperiod; in relative terms uptake accelerated twice as fast as uptake. Fescue always absorbed more than but timothy showed a preference for during part of the dark period. The results are interpreted in terms ofthe hypothesis that diurnally fluctuating sink-strengthfor nutrients is the primary determinant of nutrient transportrates, although uptake may become temporarily uncoupled fromnutrient demand during periods of physiological stress or perturbation,such as towards the end of the dark period, during which uptakerates are determined by factors (e.g. carbohydrate supply) otherthan current nutrient demand. Key words: Ammonium, diurnal variation, Gramineae, ion uptake, nitrate, potassium, regulation 相似文献
17.
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
18.
19.
Developmental Responses to Drought and Abscisic Acid in Sunflower Roots: I. ROOT GROWTH, APICAL ANATOMY, OSMOTIC ADJUSTMENT 总被引:1,自引:0,他引:1
ROBERTSON J. MASON; HUBICK KERRY T; YEUNG EDWARD C.; REID DAVID M 《Journal of experimental botany》1990,41(3):325-327
Aeroponically grown sunflower seedlings (Helianthus annuus L.cv. Russian Giant) were droughted or treated with abscisic acid(ABA) for 7 d. Drought stress prompted a three-phase growthresponse in sunflower roots: an initial phase of increased rootelongation was followed by a period of almost complete inhibitionbetween about 6 h and 72 h; this was followed, in turn, by aphase of partial recovery in the rate of root elongation. Droughtdecreased the size of the apical meristem as cells in the proximalregion of the meristem vacuolated and elongated. Root-to-shootbiomass ratios (R:S) increased initially but declined after72 h. Drought stress decreased water potential () and osmoticpotential ( and increased turgor pressure p in the apical 30mm of the roots. These initial changes were transitory, lastingabout 3 h. Thereafter, and began to rise; p fell back to controllevels. In the later stages of treatment, fell as the stressgrew more severe, but fp was maintained by osmotic adjustment.Desiccation for 1 h increased turgor pressures in excised 30mm apical segments. The transitory increase in root elongationwas contemporary with the initial rise in p in the root apices,while the periods of greatest inhibition and partial recoveryin root elongation were contemporary with the periods of declineand partial recovery in the length of the apical meristem respectively.The inhibition of root elongation and the anatomical changesin the root apices were not determined by loss of turgor orlack of photosynthate, but rather appeared to be an active responseby the meristem to a drop in external . Treatment with ABA triggeredmany of the same changes as drought stress: ABA promoted a three-phasegrowth response, increased R:S, triggered the same initial changesin , , and p, increased p in excised 3.0 mm apical segments,and induced the same pattern of anatomical changes in the rootapices as drought stress. It is proposed that ABA mediates drought-inducedchanges in the primary development of sunflower roots. Key words: Abscisic acid, apical meristem, drought, osmotic adjustmen 相似文献
20.
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