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1.
Photosynthetic activity of the calyx, green shoulder, pericarp, and locular parenchyma of tomato fruit 总被引:5,自引:1,他引:4
Photosynthesis of tomato fruit was studied using green fruit from six
heritage cultivars of Lycopersicon esculentum Mill.
and one of Lycopersicon pimpinellifolium. Chlorophyll
concentrations in the green shoulder, pericarp and locular parenchyma of
the fruit were determined and the apparent photosynthetic electron
transport activity (ETR) and chlorophyll fluorescence quenching
characteristics of these tissues and the calyx were compared. In all
cultivars, green shoulder formation, apparent as intense pigmentation of
the proximal pericarp shoulder, was positively related to the degree of
shading of the fruit during development. Appearing as a photosynthetic
adaptive trait for increasing the photoautotrophic capacity of fruit grown
under low light, the green shoulder contained 17-57% of the total pericarp
chlorophyll content. The pericarp below the green shoulder had lower
chlorophyll a+b. At a photon flux
density (PFD) of 1200 mol
m-2 s-1, different fruit
tissues were found to have different levels of ETR. In 'Yellow Pear', the
upper surface of the calyx had an ETR of 154 mol m-2
s-1, while the lower surface had an ETR of 88
mol m-2 s-1. On the
green shoulder, ETR was 203 mol m-2
s-1, whereas in the pericarp distal to the green
shoulder, ETR was 97 mol m-2
s-1. In the locular parenchyma, ETR was 66
mol m-2 s-1. This
trend towards a lower ETR in distal and internal fruit tissues appeared to
indicate a shift towards a more shade-type photosynthesis. Concomitant with
this shift were changes in chlorophyll fluorescence quenching
characteristics. Generally when tissues displayed reduced levels of ETR
they also displayed a faster decrease in the photochemical quenching
coefficient qp and a more rapid diversion of absorbed
photon energy to non-photosynthetic activity found in the calyx, green
shoulder, pericarp, and locular parenchyma suggest that all of these
tissues have significant roles in CO2 scavenging and the provision of
carbon assimilates. The potential role of fruit photosynthesis in
influencing the fruit acid to sugar ratio and hence fruit quality is
discussed. 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.
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
4.
The changes in photosynthetic activity and composition of pigments induced
by changes in temperature were examined in the third leaf of three
chilling-tolerant and three chilling-sensitive genotypes of maize
(Zea mays L.). The plants were grown under a
controlled environment at a photon flux density of 550 mol m-2
s-1, a 12 h photoperiod and at a suboptimal
temperature of 14/12 C (day/night) until the
full expansion of the third leaf. After this treatment, the
chilling-tolerant genotypes, when compared with the sensitive ones,
displayed a higher photosynthetic activity, a higher content of chlorophyll
(Chl) a+b, a higher Chl
a/b ratio, a larger total carotenoid pool size as well
as a different carotenoid composition. When temperature was subsequently
increased to 24/22 C for 3 d the composition
of the pigments changed, but the chilling-sensitive genotypes, while
adjusting their lower Chl a/b ratio and their
different carotenoid composition, were unable to adjust their lower content
of chlorophyll, their smaller total carotenoid pool size or their lower
photosynthetic performance. Moreover, while the chilling-tolerant genotypes
converted the most part of zeaxanthin to violaxanthin in the xanthophyll
cycle, the chilling-sensitive genotypes retained high amounts of
zeaxanthin. The changes in pigment composition that occurred over the 3 d
at 24/22 °C were largely conserved when the plants were returned to
14/12 °C, but photosynthetic activity decreased and zeaxanthin
accumulated again. The results suggest that the capability of the
chilling-tolerant genotypes, when compared with the sensitive ones, to
retain high amounts of pigments and to form a competent photosynthetic
apparatus at low temperature is the basis for their more vigorous growth in
cool climates. 相似文献
5.
High-light damage in air-dry thalli of Lobaria
pulmonaria were measured in the laboratory as reductions in
maximal PSII efficiency (Fv/Fm)
after a 48 h recovery in a hydrated state at low light to account for
permanent damage. Thalli treated with the lowest light dose (90 mol photons
m-2) recovered normal
Fv/Fm-values with increasing irradiances (400-700 nm)
up to 1000 mol photons
m-2 s-1. Doubling this dose
lowered the threshold level for damage from 1000 to 320 mol photons m-2
s-1, and reduced
Fv/Fm at 1000 mol
photons m-2 s-1 by more than
50%. A second doubling of the dose to 360 mol photons
m-2 caused damage at 200 mol photons
m-2 s-1, and a nearly
complete cessation of PSII efficiency occurred at 1000 mol photons
m-2 s-1. No reciprocity of
irradiance and duration of illumination for PSII function was found. The
measured time-dependent decrease in
Fv/Fm was remarkably similar for
the naturally coupled, but artificially separated, light and temperature
factors. Therefore, the damage of high light on desiccated L.
pulmonaria seemed to be an additive effect of high irradiance
and high temperatures. Air-dry thalli were highly heat susceptible, being
affected already at temperatures around 40C.
Logging operations in forests are likely to raise the solar radiation at
remaining lichen sites to destructive levels.Keywords:
Lichens, high-light damage, heat stress, poikilohydric
organisms, reciprocity.
相似文献
6.
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
7.
Hydrothermal time analysis of tomato seed germination responses to priming treatments 总被引:5,自引:1,他引:4
Controlled hydration of seeds followed by drying (seed priming) is used to
break dormancy, speed germination, and improve uniformity of radicle
emergence. To date, empirical trials are used to predict optimal priming
conditions for a given seed lot. Since priming is based upon seed water
relations, it was hypothesized that the sensitivity of germination to
reduced water potential before priming might be mechanistically related to,
and therefore predictive of, priming responsiveness. Analyses of
germination of 13 tomato (Lycopersicon esculentum
Mill.) seed lots at two temperatures (15C
and 20C) and three water potentials (0,
-0.28 and -0.43 MPa) showed that seed lot germination responses could be
quantitatively characterized by parameters derived from thermal time,
hydrotime, and hydrothermal time models
(R20.73-0.99). Six of the seed
lots were primed at two temperatures (15°C and 20°C) and
three water potentials (-1.0, -1.5 and -2.0 MPa) for various durations,
dried, and their subsequent germination rates analysed according to
hydropriming time and hydrothermal priming time models. The responses of
germination rates to priming were characterized by hydropriming time
(HP) and hydrothermal priming time (HTP) constants and
the minimum water potential (min) and temperature
(Tmin) for achieving a priming effect. The values of
min and Tmin varied relatively little among
tomato seed lots, and the generalized values of min=2.39 MPa and
Tmin=9.10°C accounted for 74% (15°C),
57% (20°C), and 62% (across both temperatures) of the increase in
germination rates following priming. Nonetheless, while the hydrothermal
time models described germination patterns both before and after priming,
there was relatively little predictive relationship between
them. 相似文献
8.
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
9.
Stomatal Control of Photosynthesis of Eucalyptus globulus Labill. Trees under Field Conditions in Portugal 总被引:4,自引:0,他引:4
Pereira, J. S., Tenhunen, J. D. and Lange, O. L. 1987. Stomatalcontrol of photosynthesis of Eucalyptus globulus Labill. treesunder field conditions in Portugal.J. exp. Bot. 38: 16781688. Stomatal behaviour of adult leaves of Eucalyptus globulus treeswas studied under field conditions in Portugal. In the absenceof severe plant water stress stomata were open when the summedtotal of photosynthetically active photon flux density incidenton both leaf surfaces was above 100 µmol m2s1 and leafconductance to water vapour reached 245 mmol m 2 s1 on a total(both epidermes) leaf area basis. The stomata of both leaf epidermesresponded similarly to changes in solar radiation and waterstress. Water stress resulted in decreasing daily maxima inleaf conductance as predawn leaf water potential decreased.Maximal leaf conductance decreased to less than 50 mmol m 2s 1 when predawn leaf water potential decreased below 1·0MPa. At similar values of predawn leaf water potential stomatawere more closed as the leaf to air water vapour partial pressuredifference increased. The effect of increasing air dryness onstomata was greatest at high predawn leaf water potential. Dailymaxima in photosynthetic rates and in leaf conductance werelinearly related to one another in spring and summer. Both decreasedwith increase in leaf water stress. In autumn and winter, increasesin leaf conductance occurring under natural conditions duringthe course of the day were not necessarily accompanied by increasesin net photosynthesis. Stomata were more closed in the afternoonthan in the morning at the same rates of net photosynthesis,temperature or leaf to air water vapour partial pressure difference. Key words: Eucalyptus globulus,, photosynthesis, stomata, water stress. 相似文献
10.
Apical abortion in calabrese (Brassica oleracea var.
italica), a highly destructive disorder which occurs
in overwintered transplants, has been investigated using a model system in
which blindness (abortion of the apical meristem) can be reproducibly and
predictably induced. An initial experiment examined the susceptibility of
12 cultivars to apical abortion when grown throughout a winter period under
commercial conditions. Three of those varieties showed very high levels of
blindness (100%). Subsequently, plants of the susceptible cultivar PETO
7204 were subjected to an inductive period of low light intensity (30
mol m-2
s-1) and low temperature (4 C). Apical meristematic cells of all plants ceased
mitotic activity within 3 d of being transferred to a regime comprising
higher light intensity (100 mol
m-2 s-1) and temperature (15
C). Using this system the structures of
normal apices were compared with those which became blind. Blindness was
characterized by a cessation of leaf primordium production by the
vegetative apex, the last formed primordium growing on in some cases to
form a mature normal leaf, or in others, a deformed structure known as a
whip-tail. The inactive apical bud became embedded in the tissues of this
last-formed structure. The cells of the inactivated apical bud remained
alive, but lost their meristematic capability, becoming enlarged, highly
vacuolated parenchyma cells with amyloplasts.Keywords:
Apical abortion, apical meristem, blindness, calabrese.
相似文献
11.
The effect of rhizosphere dissolved inorganic carbon on gas exchange characteristics and growth rates of tomato seedlings 总被引:2,自引:0,他引:2
The possibility that an enhanced supply of dissolved inorganic carbon
(DIC=CO2+HCO3-) to the root solution could increase
the growth of Lycopersicon esculentum (L.) Mill. cv.
F144 was investigated under both saline and non-saline root medium
conditions. Tomato seedlings were grown in hydroponic culture with and
without NaCl and the root solution was aerated with CO2 concentrations in
the range between 0 and 5000 mol
mol-1. The biomass of both control and
salinity-stressed plants grown at high temperatures (daily maximum of
37C) and an irradiance of 1500 mol m-2
s-1 was increased by up to 200% by enriched
rhizosphere DIC. The growth rates of plants grown with irradiances of less
than 100 mol m-2 s-1
were increased by elevated rhizosphere DIC concentrations only when grown
at high shoot temperatures (35C) or with
salinity 28°C). At high light intensities, the photosynthetic rate,
the CO2 and light-saturated photosynthetic rate (jmax)
and the stomatal conductance of plants grown at high light intensity were
lower in plants supplied with enriched compared to ambient DIC. This was
interpreted as 'down-regulation' of the photosynthetic system in plants
supplied with elevated DIC. Labelled organic carbon in the xylem sap
derived from root DI14C incorporation was found to
be sufficient to deliver carbon to the shoot at rates equivalent to 1% and
10% of the photosynthetic rate of the plants supplied with ambient- and
enriched-DIC, respectively. It was concluded that organic carbon derived
from DIC incorporation and translocated in the xylem from the root to the
shoot may provide a source of carbon for the shoots, especially under
conditions where low stomatal conductance may be advantageous, such as
salinity stress, high shoot temperatures and high light
intensities. 相似文献
12.
An improved strain-gauge device for continuous field measurement of stem and fruit diameter 总被引:7,自引:2,他引:5
An improved strain-gauge dendrometer was tested on apple (Pyrus
malus L.) tree trunks and fruit to measure thickness dynamics.
The sensor is similar to previous devices, but is more flexible allowing
for a greater range of thickness change before it has to be physically
reset. The practical resolution of the measurement system is given as one
standard deviation about the mean of 51 observations taken on an Invar
metal alloy in the field when temperatures ranged between 16C and 17C. The mean
of these observations was 3.68356 mm with one standard deviation of 0.00947
mm. There is a positive correlation between temperature and sensor output
having a slope of 2.96 m°C-1. For a typical
daily temperature change of 21°C, this causes an apparent change of
62 m. Stem thickness varied 0.7 mm diurnally
with maximum values at night and minimum values during the day. Apple fruit
diameter increased 3.3 mm over the 15 d period.Keywords:
Strain gauge dendrometer, plant stem and fruit thickness sensor,
plant water status, growth.
相似文献
13.
Effects of water stress on photosystem II photochemistry and its thermostability in wheat plants 总被引:19,自引:1,他引:18
Modulated chlorophyll fluorescence, rapid fluorescence induction kinetics
and the polyphasic fluorescence transients (OJIP) were used to evaluate
PSII photochemistry in wheat plants exposed to water stress and/or heat
stress (25-45C). Water stress showed no
effects on the maximal quantum yield of PSII photochemistry
(Fv/Fm), the rapid fluorescence
induction kinetics, and the polyphasic fluorescence transients in
dark-adapted leaves, indicating that water stress had no effects on the
primary photochemistry of PSII. However, in light-adapted leaves, water
stress reduced the efficiency of excitation energycapture by open PSII
reaction centres (F'v/F'm) and
the quantum yield of PSII electron transport (PSII), increased
the non-photochemical quenching (qN) and showed no effects on the
photochemical quenching (qP). This suggests that water stress modified the
PSII photochemistry in the light-adapted leaves and such modifications may
be a mechanism to down-regulate the photosynthetic electron transport to
match a decreased CO2 assimilation. In addition, water stress also modified
the responses of PSII to heat stress. When temperature was above 35C, thermostability of PSII was strongly enhanced in
water-stressed leaves, which was reflected in a less decrease in
Fv/Fm, qP,
F'v/F'm, and PSII in
water-stressed leaves than in well-watered leaves. There were no
significant variations in the above fluorescence parameters between
moderately and severely water-stressed plants, indicating that the moderate
water-stressed plants, indicating that the moderate water stress treatment
caused the same effects on thermostability of PSII as the severe treatment.
It was found that increased thermostability of PSII may be associated with
an improvement of resistance of the O2-evolving complex and the reaction
centres in water-stressed plants to high temperature.Key
words: Chlorophyll fluorescence, heat stress, photosystem II
photochemistry, water stress, wheat (Tritium aestivum
L.).
相似文献
14.
Foliar dehydration tolerance of twelve deciduous tree species 总被引:1,自引:0,他引:1
The potential for foliar dehydration tolerance and maximum capacity for
osmotic adjustment were compared among 12 temperate, deciduous tree
species, under standardized soil and atmospheric conditions. Dehydration
tolerance was operationally defined as lethal leaf water potential
(); the of the last remaining leaves surviving a
continuous, lethal soil drying episode. Nyssa
sylvatica Marsh., and Liriodendron
tulipifera L. were most sensitive to dehydration, having lethal
leaf of -2.04 and -2.38 MPa, respectively. Chionanthus
virginicus L., Quercus prinus L.,
Acer saccharum Marsh., and Quercus
acutissima Carruthers withstood the most dehydration, with
leaves not drying until leaf dropped to -5.63 MPa or below.
Lethal leaf (in MPa) of other, intermediate species were:
Quercus rubra L. (-3.34), Oxydendrum
arboreum (L.) D.C. (-3.98), Halesia
carolina L. (-4.11), Acer rubrum L.
(-4.43), Quercus alba L. (-4.60), and Cornus
florida L. (-4.88). Decreasing lethal leaf was
significantly correlated with increasing capacity for osmotic adjustment.
C. virginicus and Q. acutissima
showed the most osmotic adjustment during the lethal soil drying episode,
with osmotic potential at full turgor declining by 1.73 and 1.44 MPa,
respectively. Other species having reductions in osmotic potential at full
turgor exceeding 0.50 MPa were (in MPa) Q. prinus
(0.89), A. saccharum (0.71), Q.
alba (0.68), H. carolina (0.67),
Q. rubra (0.60), and C. florida
(0.52). 相似文献
15.
Natural abundance of 15N in amino acids and polyamines from leguminous nodules: unique 15N enrichment in homospermidine 总被引:2,自引:0,他引:2
The natural 15N abundance
(15N value) in acetylpropyl derivatives of
amino acids and in ethyloxycarbonyl derivatives of polyamines was
determined using a gas chromatography/combustion/mass
spectrometer-(GC/C/MS). 15N value
determined for 12 amino acids and five polyamines by GC/C/MS were identical
to those obtained by a direct combustion method using an automatic nitrogen
and carbon analysis (ANCA) mass spectrometer, the difference being less
than 1.0% in most cases. The GC/C/MS
method was used to analyse 15N values in
the amino acids and polyamines from root nodules of pea and faba bean and
from stem nodules of Sesbania rostrata. The analysis
of 15N values revealed that homospermidine
had high 15N values, as much as +40%, while
the amino acids investigated had 15N values
between -3 and +6%, putrescine between +2 and +8%, cadaverine between +1
and +7%, spermidine between -2 and +4%, and spermine between 0 and +6%. The
mechanism of 15N enrichment in homospermidine is
discussed. 相似文献
16.
17.
Nitrogen deficiency reduces the photosynthetic capacity of both C3 and C4
plants. The regulation of photosynthetic gas exchange in eight clones of
the C4 grass, sugarcane (Saccharum spp.), grown at
three levels of N availability was studied to determine whether N stress
diminishes the efficiency of the C4 CO2 concentrating system in addition to
reducing overall rates of photosynthesis. The quantum yield for CO2 uptake
decreased linearly with decreasing leaf N content. Genetic variation in
quantum yield at a given level of N supply was also observed. Leaf tissue
carbon isotope discrimination () increased linearly with
decreasing quantum yield. Concurrent determinations of the prevailing ratio
of intercellular to ambient partial pressure of CO 2
(pi/pa) during leaf gas exchange
suggested that the observed variation in was almost entirely
attributable to variation in bundle sheath leakiness to CO2 ()
rather than pi/pa. Taken
together, these results point to substantial environmental and genetic
variation in the efficiency of the CO2 concentrating system in sugarcane.
Reduced partitioning of carboxylase activity to ribulose-1,5-bisphosphate
carboxylase relative to phosphoenolpyruvate carboxylase in N-deficient
plants suggested that the associated increase in and decline in
quantum yield may have been attributable largely to a decline in C3 cycle
activity in the bundle sheath relative to C4 cycle activity in the
mesophyll. Quantum yield and intrinsic water use efficiency (WUE) were
negatively correlated. In contrast with the trade-off between intrinsic
light- and water use efficiency, photosynthetic nitrogen-use efficiency and
intrinsic WUE were positively correlated. 相似文献
18.
Influence of UV-B radiation and Cd2+ on chlorophyll fluorescence, growth and nutrient content in Brassica napus 总被引:8,自引:0,他引:8
The possible interaction of two stresses, UV-B radiation and cadmium,
applied simultaneously, was investigated in Brassica
napus L. cv. Paroll with respect of chlorophyll fluorescence,
growth and uptake of selected elements. Plants were grown in nutrient
solution containing CdCl2, (0, 0.5, 2 or 5 M)
and irradiated with photosynthetically active radiation
(PAR, 400-700 nm, 800 mol m-2
s-1) with or without supplemental ultraviolet-B
radiation (UV-B, 280-320 nm, 15 kJ m-2
d-1, weighted irradiance). After 14 d of treatment,
the most pronounced effects were found at 2 and 5 M CdCl2 with and
without supplemental UV-B radiation. Exposure to cadmium significantly
increased the amount of Cd in both roots and shoots. In addition, increases
occurred in the concentrations of Fe, Zn, Cu, and P in roots, while K was
reduced. In shoots the S content rose significantly both in the presence
and absence of UV-B radiation, while significant increases in Mg, Ca, P,
Cu, and K occurred only in plants exposed to Cd and UV-B radiation.
Manganese decreased significantly under the combined exposure treatment.
The rise in S content may have been due to stimulated glutathione and
phytochelatin synthesis. Cadmium exposure significantly decreased root dry
weight, leaf area, total chlorophyll content, carotenoid content, and the
photochemical quantum yield of photosynthesis. As an estimation of energy
dissipation processes in photosynthesis, non-photochemical quenching
(qNPQ) was measured using a pulse amplitude modulated
fluorometer. The qNPQ increased with increasing Cd,
while the combination of cadmium and UV-B reduced the
qNPQ compared to that in plants exposed only to
cadmium or UV-B radiation. The chlorophyll a:b ratio
showed a reduction with UV-B at no or low Cd concentrations (0 M,
0.5 M CdCl2), but not at the higher Cd concentrations used (2
M, 5 M CdCl2). Thus in some instances there appeared to
be a UV-B and Cd interaction, while in other plants response could be
attributed to either treatment alone.Keywords:
Brassica napus, cadmium, ultraviolet-B
radiation.
相似文献
19.
ACOCK B.; CHARLES-EDWARDS D. A.; FITTER D. J.; HAND D. W.; LUDWIG L. J.; WARREN WILSON J.; WITHERS A. C. 《Journal of experimental botany》1978,29(4):815-827
The rates of net photosynthesis per unit ground area by a closedcanopy of tomato plants were measured over a range of naturallight flux densities. The canopy, of leaf area index 8.6, wasdivided into three horizontal layers of equal depth. On successivedays the canopy was progressively defoliated in layers fromthe ground upwards, allowing the photosynthetic contributionfrom individual leaf layers to be determined. The uppermostlayer, 23% of the total leaf area, assimilated 66% of the netCO2 fixed by the canopy and accounted for a similar percentageof the total leaf respiration. Net photosynthesis versus light response curves for individualleaves from different positions within the canopy were alsoobtained. Leaf conductances to CO2 transfer and the dark respirationrates of leaves from the uppermost leaf layer were approximatelyten times those from the lowest layer. The canopy data were analysed using a simple model which assumedthat the canopy was composed of leaves with identical photosyntheticand respiratory characteristics. The model fitted the data andallowed the characteristics of an idealized leafto be estimated. The estimated values of the leaf light utilizationefficiency, ,and the leaf conductance CO2 transfer, , were similarto values directly determined for individual leaves in the uppermostleaf layer and the estimated rate of leaf dark respiration,Rd, corresponded to measured rates for leaves much lower inthe canopy. The simple model may be used to examine gross effectsof crop environment on the leaf photosynthetic characteristicof an idealized leaf, but cannot be used to predictaccurately canopy net photosynthesis from the photosyntheticand respiratory characteristics of any single real leaf. A moredetailed model, developed to allow explicitly for the observedvariation in and Rd within the canopy is appropriate for thispurpose. 相似文献
20.
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