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1.
The differences in pigment levels, photosynthetic activity and the chlorophyll fluorescence decrease ratio R
Fd (as indicator of photosynthetic rates) of green sun and shade leaves of three broadleaf trees (Platanus acerifolia Willd., Populus alba L., Tilia cordata Mill.) were compared. Sun leaves were characterized by higher levels of total chlorophylls a + b and total carotenoids x + c as well as higher values for the weight ratio chlorophyll (Chl) a/b (sun leaves 3.23–3.45; shade leaves: 2.74–2.81), and lower values for the ratio chlorophylls to carotenoids (a + b)/(x + c) (with 4.44–4.70 in sun leaves and 5.04–5.72 in shade leaves). Sun leaves exhibited higher photosynthetic rates P
N on a leaf area basis (mean of 9.1–10.1 μmol CO2 m−2 s−1) and Chl basis, which correlated well with the higher values of stomatal conductance G
s (range 105–180 mmol m−2 s−1), as compared to shade leaves (G
s range 25–77 mmol m−2 s−1; P
N: 3.2–3.7 μmol CO2 m−2 s−1). The higher photosynthetic rates could also be detected via imaging the Chl fluorescence decrease ratio R
Fd, which possessed higher values in sun leaves (2.8–3.0) as compared to shade leaves (1.4–1.8). In addition, via R
Fd images it was shown that the photosynthetic activity of the leaves of all trees exhibits a large heterogeneity across the
leaf area, and in general to a higher extent in sun leaves than in shade leaves. 相似文献
2.
Guruprasad K Kadur G Bhattacharjee S Swapan B Kataria S Sunita K Yadav S Sanjeev Y Tiwari A Arjun T Baroniya S Sanjay B Rajiv A Abhinav R Mohanty P 《Photosynthesis research》2007,94(2-3):299-306
Exclusion of UV (280–380 nm) radiation from the solar spectrum can be an important tool to assess the impact of ambient UV
radiation on plant growth and performance of crop plants. The effect of exclusion of UV-B and UV-A from solar radiation on
the growth and photosynthetic components in soybean (Glycine max) leaves were investigated. Exclusion of solar UV-B and UV-B/A radiation, enhanced the fresh weight, dry weight, leaf area
as well as induced a dramatic increase in plant height, which reflected a net increase in biomass. Dry weight increase per
unit leaf area was quite significant upon both UV-B and UV-B/A exclusion from the solar spectrum. However, no changes in chlorophyll
a and b contents were observed by exclusion of solar UV radiation but the content of carotenoids was significantly (34–46%) lowered.
Analysis of chlorophyll (Chl) fluorescence transient parameters of leaf segments suggested no change in the F
v/F
m value due to UV-B or UV-B/A exclusion. Only a small reduction in photo-oxidized signal I (P700+)/unit Chl was noted. Interestingly the total soluble protein content per unit leaf area increased by 18% in UV-B/A and 40%
in UV-B excluded samples, suggesting a unique upregulation of biosynthesis and accumulation of biomass. Solar UV radiation
thus seems to primarily affect the photomorphogenic regulatory system that leads to an enhanced growth of leaves and an enhanced
rate of net photosynthesis in soybean, a crop plant of economic importance. The presence of ultra-violet components in sunlight
seems to arrest carbon sequestration in plants.
An erratum to this article can be found at 相似文献
3.
Plant β-glucosidases catalyze the hydrolysis of glycosidic linkages and play a vital role in defense against pathogens and
stress. The present work investigated the relationship between leaf development and β-glucosidase protein content in Olea europea L. (cv. Picual) leaves. The total chlorophyll content increased with leaf age in current-season leaves. Immunoblot analysis
revealed that the content of 61 kD protein of β-glucosidase also increased with leaf age, and that the enzyme existed in three
isoforms (pI 5.8–6.2). Statistical analysis indicated a strong correlation between chlorophyll and β-glucosidase protein contents. 相似文献
4.
Thermal and chlorophyll-fluorescence imaging distinguish plant-pathogen interactions at an early stage 总被引:10,自引:0,他引:10
Chaerle L Hagenbeek D De Bruyne E Valcke R Van Der Straeten D 《Plant & cell physiology》2004,45(7):887-896
Different biotic stresses yield specific symptoms, owing to their distinct influence on a plant's physiological status. To monitor early changes in a plant's physiological status upon pathogen attack, chlorophyll fluorescence imaging (Chl-FI) and thermography, which respectively visualize photosynthetic efficiency and transpiration, were carried out in parallel for two fundamentally different plant-pathogen interactions. These non-destructive imaging techniques were able to visualize infections at an early stage, before damage appeared. Under growth-room conditions, a robotized set-up captured time series of visual, thermal and chlorophyll fluorescence images from infected regions on attached leaves. As a first symptom of the plant-virus interaction between resistant tobacco and tobacco mosaic virus (TMV), thermal imaging detected a local rise in temperature while Chl-FI monitored a co-localized increase in fluorescence intensity. Chl-FI also revealed pre-symptomatic high-intensity spots for the plant-fungus system sugar beet-Cercospora beticola. Concomitantly, spots of lower temperature were monitored with thermography, in marked contrast with our observations on TMV-infection in tobacco. Knowledge of disease signatures for different plant-pathogen interactions could allow early identification of emerging biotic stresses in crops, facilitating the containment of disease outbreaks. Presymptomatic monitoring clearly opens perspectives for quantitative screening for disease resistance, either on excised leaf pieces or attached leaves. 相似文献
5.
A cheap chlorophyll (Chl) a fluorescence imaging system was developed for measuring leaf areas of 30×45 cm. Uniform saturating irradiances were created using CuSO4 filtered radiation from stroboscopes. The system was tested using maize leaves treated with diuron. Comparison was made with a small-area-measuring pulse amplified modulation Chl fluorometer. 相似文献
6.
This contribution is a practical guide to the measurement of the different chlorophyll (Chl) fluorescence parameters and gives
examples of their development under high-irradiance stress. From the Chl fluorescence induction kinetics upon irradiation
of dark-adapted leaves, measured with the PAM fluorometer, various Chl fluorescence parameters, ratios, and quenching coefficients
can be determined, which provide information on the functionality of the photosystem 2 (PS2) and the photosynthetic apparatus.
These are the parameters Fv, Fm, F0, Fm′, Fv′, NF, and ΔF, the Chl fluorescence ratios Fv/Fm, Fv/F0, ΔF/Fm′, as well as the photochemical (qP) and non-photochemical quenching coefficients (qN, qCN, and NPQ). qN consists of three components (qN = qE + qT + qI), the contribution of which can be determined via Chl fluorescence relaxation kinetics measured in the dark period after the induction kinetics. The above Chl fluorescence
parameters and ratios, many of which are measured in the dark-adapted state of leaves, primarily provide information on the
functionality of PS2. In fully developed green and dark-green leaves these Chl fluorescence parameters, measured at the upper
adaxial leaf side, only reflect the Chl fluorescence of a small portion of the leaf chloroplasts of the green palisade parenchyma
cells at the upper outer leaf half. Thus, PAM fluorometer measurements have to be performed at both leaf sides to obtain information
on all chloroplasts of the whole leaf. Combined high irradiance (HI) and heat stress, applied at the upper leaf side, strongly
reduced the quantum yield of the photochemical energy conversion at the upper leaf half to nearly zero, whereas the Chl fluorescence
signals measured at the lower leaf side were not or only little affected. During this HL-stress treatment, qN, qCN, and NPQ increased in both leaf sides, but to a much higher extent at the lower compared to the upper leaf side. qN was the best indicator for non-photochemical quenching even during a stronger HL-stress, whereas qCN and NPQ decreased with progressive stress even though non-photochemical quenching still continued. It is strongly recommended
to determine, in addition to the classical fluorescence parameters, via the PAM fluorometer also the Chl fluorescence decrease ratio RFd (Fd/Fs), which, when measured at saturation irradiance is directly correlated to the net CO2 assimilation rate (P
N) of leaves. This RFd-ratio can be determined from the Chl fluorescence induction kinetics measured with the PAM fluorometer using continuous saturating
light (cSL) during 4–5 min. As the RFd-values are fast measurable indicators correlating with the photosynthetic activity of whole leaves, they should always be
determined via the PAM fluorometer parallel to the other Chl fluorescence coefficients and ratios. 相似文献
7.
Petioles of intact cabbage leaves were placed in azadirachtin solutions for 24 h. Azadirachtin or active metabolites of this
compound appeared to be translocated systemically as performance of first instar larvae ofPieris brassicae L. placed on disks from those leaves was affected. The position within a leaf from which disks were excised did not affect
the extent of these effects, indicating a homogeneous distribution of active compounds in the laminar tissue. At doses ranging
from 1–10 ppm of azadirachtin in the solution taken up by the leaves, gain of larval fresh weight and leaf area consumed were
reduced. These effects were dose dependent up to 60–90 ppm. At 10 ppm and higher doses no larva reached the second instar
within 72 h. Mortality during the 72 h period was highest at 10 ppm, due to the coincidence of lethal action with ecdysis
in combination with the effect on developmental rate. Azadirachtin solutions applied directly to the surface of leaf disks
in order to produce known doses on a leaf fresh weight basis gave results similar to the systemic treatment for weight gain,
leaf area consumed and developmental rate, while mortality was higher in the latter treatment. 相似文献
8.
P. Thomas J. B. Mythili K. S. Shivashankara 《In vitro cellular & developmental biology. Plant》2000,36(6):537-542
Summary Triploid watermelon (Citrullus lanatus [Thunb.] Matsum. & Nakai) Arka Manik cultures exhibited a general pale color and yellowing of lower leaves by 3–4 wk following
subculturing to fresh medium. Protecting the medium from light by covering the surface with sterile aluminum foil significantly
improved leaf color and chlorophyll content by 50–60%. Raising the concentration of FeNa2EDTA (Fe-EDTA) in the light-exposed medium from the normal level (100 μM) to 150 or 200 μM significantly increased the leaf chlorophyll two- to threefold, suggesting that the light-induced effect was mainly attributable
to photo-oxidation of Fe-EDTA. Fe-EDTA supplementation also resulted in better expansion and lobe formation of upper leaves,
a reduction in internode length, an increase in the number of nodes, and a significant improvement in propagation rate. There
was also a reduction in axillary sprout growth at elevated Fe-EDTA levels, indicating a more prominent apical dominance effect
and a reduction in the number and vigor of tendrils. Increasing the Fe-EDTA level in the medium to 150 μM is suggested for routine micropropagation of triploid watermelon, in order to compensate for the photo-oxidative loss of
Fe-EDTA. 相似文献
9.
M. Lang H. K. Lichtenthaler Malgorzata Sowinska P. Summ Francine Heisel 《Plant biology (Stuttgart, Germany)》1994,107(4):230-236
Laser-induced fluorescence images of the leaf of an aurea mutant of Nicotiana tabacum were recorded for the blue and green fluorescence at 440 and 520 nm and the red chlorophyll fluorescence at 690 and 735 nm. The results obtained were compared with direct measurements of the fluorescence emission spectra of leaves using a conventional spectrofluorometer. The highest emission of blue (F440) and green fluorescence (F520) within the leaf was found in the leaf veins, particularly the main leaf vein. In contrast, the intercostal fields of leaves, which exhibited the highest chlorophyll content, showed only a very low blue and green fluorescence emission, which was much lower than the red and far-red chlorophyll fluorescence emission bands (F690 and F735). Correspondingly, the ratio of blue to red leaf fluorescence F440/F690 of upper and lower leaf side was much higher in the leaf veins (values 1.2 to 1.5) than in intercostal fields (values of 0.6 to 0.7). The results also demonstrated that in the intercostal fields the major part of the blue-green fluorescence was reabsorbed by chlorophylls and carotenoids. A partial reabsorption of the red fluorescence band near 690 nm by leaf chlorophyll took place, but did not affect the far-red fluorescence band near F735. As a consequence the chlorophyll fluorescence ratio F690/F735 exhibited significantly higher values in the chlorophyll-poor leaf vein regions (1.7 to 1.8) than in the chlorophyll-rich intercostal fields (0.8 to 1.3). Imaging spectroscopy of leaves was shown to be much more precise than the screening of fluorescence signatures by conventional fluorometers. It clearly demonstrated that the blue-green fluorescence and the red chlorophyll fluorescence of leaves exhibit an inverse contrast to each other. The advantage of the fluorescence imaging spectroscopy, which allows the simultaneous screening of the whole leaf surface and distinct parts of it, and its possible application in the detection of stress effects or local damage by insects and pathogens, is discussed. 相似文献
10.
The kinetics of formation of esterified chlorophyll in etiolated barley (Hordeum vulgare L.) leaves after illumination with a single flash was studied. It was found that after partial (14–24%) and after full photoreduction
of protochlorophyllide, the same quantity of esterified products appear during the first 5 s after the flash. The rest of
formed chlorophyllide was esterified in a slow process during at least 30 min at 15 °C. The product of fast esterification
can be correlated with ‘short-wavelength’ chlorophyll, characterized by a fluorescence emission peak at 673–675 nm. This is
the only chlorophyll form detectable within 20 s after partial (14%) photoconversion, and it appears at the same time as the
shoulder of the chlorophyll(ide) fluorescence after full photoconversion. The main product after full photoconversion shows
a fluorescence at 689 nm shifting in darkness within 15 s to 693 nm and then within 30 min to 682 nm (Shibata shift). The
slow esterification proceeds with similar kinetics as the Shibata shift. We propose that the fast esterification of only part
of total chlorophyllide after full photoconversion of protochlorophyllide in etiolated leaves reflects the restricted capacity
of the esterifying system. The slow esterification of the residual chlorophyllide may be time-limited by its release from
protochlorophyllide oxidoreductase, by disaggregation of prolamellar bodies and by diffusion of tetraprenyl diphosphates towards
chlorophyll synthase.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
S. C. Debnath 《In vitro cellular & developmental biology. Plant》2009,45(2):122-128
An efficient system to regenerate shoots on excised leaves of greenhouse-grown wild lowbush blueberry (Vaccinium angustifolium Ait.) was developed in vitro. The effect of thidiazuron (TDZ) on adventitious bud and shoot formation from apical, medial, and basal segments of the leaves
was tested. Leaf cultures produced multiple buds and shoots with or without an intermediary callus phase on 2.3–4.5 μM TDZ
within 6 wk of culture initiation. The greatest shoot regeneration came from young expanding basal leaf segments positioned
with the adaxial side touching the culture medium and maintained for 2 wk in darkness. Callus development and shoot regeneration
depended not only on the polarity of the explants but also on the genotype of the clone that supplied the explant material.
TDZ-initiated cultures were transferred to medium containing 2.3–4.6 μM zeatin and produced usable shoots after one additional
subculture. Elongated shoots were dipped in 39.4 mM indole-3-butyric acid powder and planted on a peat:perlite soilless medium
at a ratio of 3:2 (v/v), which yielded an 80–90% rooting efficiency. The plantlets were acclimatized and eventually established in the greenhouse
with 75–85% survival. 相似文献
12.
Morphological, anatomical, biochemical and physiological traits of sun and shade leaves of adult Quercus ilex, Phillyrea latifolia and Pistacia lentiscus shrub species co-occurring in the Mediterranean maquis at Castelporziano (Latium) were studied. Fully expanded sun leaves had 47% (mean of the three species) greater leaf mass area (LMA) and 31% lower specific leaf area (SLA) than shade leaves. Palisade parenchyma thickness contributed on an average 42% to the total leaf thickness, spongy layer 43%, upper epidermal cells 5%, and upper cuticle thickness 3%. Stomatal size was greater in sun (25.5 μm) than in shade leaves (23.6 μm). Total chlorophyll content per fresh mass was 71% greater in shade than in sun leaves, and nitrogen content was the highest in sun (13.7 mg g−1) than in shade leaves (11.8 mg g−1). Difference of net photosynthetic rates (P
N) between sun and shade leaves was 97% (mean of the three species). The plasticity index (sensu Valladares et al., New Phytol 148:79–91, 2000a) was the highest for physiological leaf traits (0.86) than for morphological, anatomical and biochemical ones. Q. ilex had the highest plasticity index of morphological, anatomical and physiological leaf traits (0.37, 0.28 and 0.71, respectively) that might explain its wider ecological distribution. The higher leaf plasticity of Q. ilex might be advantageous in response to varying environmental conditions, including global change. 相似文献
13.
Protomycopsis phaseoli (Ramak and Subram) is the causal agent of the cowpea leaf smut disease in Nigeria and not Entyloma vignae as claimed by some authors. This pathogen formed dark ash-grey to sooty-black lesions of 3–10 mm in diameter, while young
lesions had yellow haloes. P. phaseoli produced dark reddish-brown chlamydospores that are globose to oval measured 23.8 μm, thick-walled and rugose. The chlamydospores
germinated and produced globose vesicles. The pathogen grew on potato dextrose agar only when the leaf tissue was dipped in
acidified water (1% H2SO4). The organism was slowly growing at 24–28 °C with snow white colour. Chlamydospores of P. phaseoli in infected cowpea leaves survived longer when buried in the soil for five months than when they were left on the soil surface
for the same period at temperatures (26–27 °C) and humidity (70–82%) prevailing in Ibadan. Destruction of leaf debris before
crop emergence, long period of rotation and no tillage cropping are suggested to prevent the onset and spread of leaf smut
disease of cowpea.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
Rosenqvist E 《Photosynthesis research》2001,70(3):299-310
Chrysanthemum inducum-hybrid `Coral Charm', Hibiscus rosa-sinensis L. `Cairo Red' and Spathiphyllum wallisii Regel `Petit' were grown in natural light in a greenhouse at three levels of irradiance using permanent shade screens. Light
acclimation of photosynthesis was characterized using modulated chlorophyll a fluorescence of intact leaves. A close correlation was found between the degree of reduction of the primary electron acceptor
QA of Photosystem II (PS II) approximated as the fluorescence parameter 1−qP, and light acclimation. The action range of 1−qP was 0–0.4 from darkness to full irradiance around noon, within the respective light treatments in the greenhouse, indicating
that most PS II reaction centres were kept open. In general, the index for electron transport (ETR) measured by chlorophyll
fluorescence was higher for high-light (HL) than intermediate-(IL) and low-light (LL) grown plants. However, HL Chrysanthemum showed 40% higher ETR than HL Hibiscus at light saturation, despite identical redox states of QA. The light acclimation of the non-radiative dissipation of excess energy in the antenna, NPQ, varied considerably between
the species. However, when normalized against qP, a strong negative correlation was found between thermal dissipation and ETR measured by chlorophyll fluorescence. To be
able to accommodate a high flux of electrons through PS II, the plants with the highest light-saturated ETR had the lowest
NPQ/qP. The possibility of using chlorophyll fluorescence for quantification of the energy balance between energy input and utilization
in PS II in intact leaves is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
We compared by chlorophyll (Chl) fluorescence imaging the effects of two strains of the same virus (Italian and Spanish strains
of the Pepper mild mottle virus — PMMoV-I and-S, respectively) in the host plant Nicotiana benthamiana. The infection was visualized either using conventional Chl fluorescence parameters or by an advanced statistical approach,
yielding a combinatorial set of images that enhances the contrast between control and PMMoV-infected plants in the early infection
steps. Among the conventional Chl fluorescence parameters, the non-photochemical quenching parameter NPQ was found to be an
effective PMMoV infection reporter in asymptomatic leaves of N. benthamiana, detecting an intermediate infection phase. The combinatorial imaging revealed the infection earlier than any of the standard
Chl fluorescence parameters, detecting the PMMoV-S infection as soon as 4 d post-inoculation (dpi), and PMMoV-I infection
at 6 dpi; the delay correlates with the lower virulence of the last viral strain. 相似文献
16.
With a flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS) the photosynthetic activity of several thousand image points of intact shade and sun leaves of beech were screened in a non-destructive way within a few seconds. The photosynthetic activity was determined via imaging the Chl fluorescence at maximum Fp and steady state fluorescence Fs of the induction kinetics (Kautsky effect) and by a subsequent determination of the images of the fluorescence decrease ratio RFd and the ratio Fp/Fs. Both fluorescence ratios are linearly correlated to the photosynthetic CO2 fixation rates. This imaging method permitted to detect the gradients in photosynthetic capacity and the patchiness of photosynthetic quantum conversion across the leaf. Sun leaves of beech showed a higher photosynthetic capacity and differential pigment ratios (Chl a/b and Chls/carotenoids) than shade leaves. Profile analysis and histogram of the Chl fluorescence yield and the Chl fluorescence ratios allow to quantify the differences in photosynthetic activity between different leaf parts and between sun and shade leaves with a high statistical significance. 相似文献
17.
Leaf senescence-like characteristics contribute to cotton's premature photosynthetic decline 总被引:6,自引:0,他引:6
Leaf and canopy photosynthesis of cotton (Gossypium hirsutum L.) declines as the crop approaches cutout, just as the assimilate needs for reproductive growth are peaking. Our objective
with this study was to determine whether this decline is due to remobilization of leaf components to support the reproductive
growth or due to some cue from the changing environmental conditions during the growing season. Field studies were conducted
in 1995–1996 at Stoneville, Mississippi, using six cotton genotypes and two planting dates (early and late), which produced
two distinctly different cotton populations reaching cutout at different times. Among the six genotypes were a photoperiod
sensitive line (non-flowering) and its counter part which had photoperiod insensitive genes backcrossed four times to the
photoperiod sensitive line (flowering). This pair was used to assess the degree that the photosynthetic decline could be attributed
to reproductive sink development. Leaf CO2-exchange rate (CER) and chlorophyll (Chl) fluorescence measurements were taken in mid-August, a period corresponding to cutout
for the early planted plots, and those leaves were collected. Leaf Chl level, soluble protein level, various soluble carbohydrate
levels and Rubisco activities were assayed on those leaves. Averaged across years, leaf CER and soluble protein levels were
reduced approximately 14% and 18%, respectively, for the early planted compared to the late planted cotton. Neither leaf Chl
levels or Chl fluorescence Fv/Fm values for Photosystem II yield were altered by the planting date. In 1996, leaves from the
non-flowering line had 12% greater Chl and 20% greater soluble protein levels than the flowering line. However, in 1996, the
CER of the early planted non-flowering line was reduced 10% compared to the late planted. Although remobilization of leaf
N to reproductive growth appears to be the principle component causing the cutout photosynthetic decline, the data also indicate
that environmental factors can play a small role in causing the decline.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Damage to primary photosynthetic reactions by drought, excess light and heat in leaves of Macroptilium atropurpureum Dc. cv. Siratro was assessed by measurements of chlorophyll fluorescence emission kinetics at 77 K (-196°C). Paraheliotropic leaf movement protected waterstressed Siratro leaves from damage by excess light (photoinhibition), by heat, and by the interactive effects of excess light and high leaf temperatures. When the leaves were restrained to a horizontal position, photoinhibition occurred and the degree of photoinhibitory damage increased with the time of exposure to high levels of solar radiation. Severe inhibition was followed by leaf death, but leaves gradually recovered from moderate damage. This drought-induced photoinhibitory damage seemed more closely related to low leaf water potential than to low leaf conductance. Exposure to leaf temperatures above 42°C caused damage to the photosynthetic system even in the dark and leaves died at 48°C. Between 42 and 48°C the degree of heat damage increased with the time of exposure, but recovery from moderate heat damage occurred over several days. The threshold temperature for direct heat damage increased with the growth temperature regime, but was unaffected by water-stress history or by current leaf water status. No direct heat damage occurred below 42°C, but in water-stressed plants photoinhibition increased with increasing leaf temperature in the range 31–42°C and with increasing photon flux density up to full sunglight values. Thus, water stress evidently predisposes the photosynthetic system to photoinhibition and high leaf temperature exacerbates this photoinhibitory damage. It seems probable that, under the climatic conditions where Siratro occurs in nature, but in the absence of paraheliotropic leaf movement, photoinhibitory damage would occur more frequently during drought than would direct heat damage.Abbreviations and symbols PFD
photon flux area density
- PSI, PSII
photosyntem I, II
-
F
M, F
O, F
V
maximum, instantaneous, variable fluorescence emission
- PLM
paraheliotropic leaf movement; all data of parameter of variation are mean ± standard error 相似文献
19.
Changes in Chlorophyll Fluorescence in Maize Plants with Imposed Rapid Dehydration at Different Leaf Ages 总被引:2,自引:0,他引:2
Z. Z. Xu G. S. Zhou Y. L. Wang G. X. Han Y. J. Li 《Journal of Plant Growth Regulation》2008,27(1):83-92
A comparison of the effects of a rapidly imposed water deficit with different leaf ages on chlorophyll a fluorescence and gas exchange was performed in maize (Zea mays L.) plants. The relationships between photosynthesis and leaf relative turgidity (RT) and ion leakage were further investigated.
Leaf dehydration substantially decreased net photosynthetic rate (A) and stomatal conductance (G
s), particularly for older leaves. With dehydration time, F
v
/F
m maintained a relatively stable level for youngest leaves but significantly decreased for the older leaves. The electron transport
rate (ETR) sharply decreased with intensifying dehydration and remained at lower levels during continuous dehydration. The
photochemical quenching of variable chlorophyll fluorescence (q
P) gradually decreased with dehydration intensity for the older leaves but increased for the youngest leaves, whereas dehydration
did not affect the nonphotochemical chlorophyll fluorescence quenching (NPQ) for the youngest leaves but remarkably decreased
it for the older leaves. The leaf RT was significantly and positively correlated with its F
v
/F
m, ETR, and q
P, and the leaf ion leakage was significantly and negatively correlated with F
v
/F
m and NPQ. Our results suggest that the photosynthetic systems of young and old leaves decline at different rates when exposed
to rapid dehydration. 相似文献
20.
This study aims to assess the photoprotective potential of desiccation-induced curling in the light-susceptible old forest
lichen Lobaria pulmonaria by using chlorophyll fluorescence imaging. Naturally curled thalli showed less photoinhibition-induced limitations in primary
processes of photosynthesis than artificially flattened specimens during exposures to 450 μmol m−2 s−1 in the laboratory after both 12- (medium dose treatment) and 62-h duration (high dose treatment). Thallus areas shaded by
curled lobes during light exposure showed unchanged values of measured chlorophyll fluorescence parameters (F
V/F
M, ΦPS II), whereas non-shaded parts of curled thalli, as well as the mean for the entire flattened thalli, showed photoinhibitory
limitation after light treatments. Furthermore, the chlorophyll fluorescence imaging showed that the typical small-scale reticulated
ridges on the upper side of L. pulmonaria caused a spatial, small-scale reduction in damage due to minor shading. Severe dry-state photoinhibition readily occurred
in flattened and light-treated L. pulmonaria, although the mechanisms for such damage in a desiccated and inactive stage are not well known. Natural curling is one strategy
to reduce the chance for serious photoinhibition in desiccated L. pulmonaria thalli during high light exposures. 相似文献