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1.
A. Pavlovič 《Photosynthetica》2011,49(2):253-258
Australian carnivorous pitcher plant Cephalotus follicularis Labill. produces two types of leaves. During the spring time, the plant produces a foliage type of noncarnivorous leaf called
lamina. Later, the second type of leaf is produced — carnivorous pitcher. Using simultaneous measurements of gas exchange
and chlorophyll (Chl) fluorescence photosynthetic efficiency of these two distinct forms of leaves were compared. In addition
stomatal density, an important component of gas exchange, and Chl concentration were also determined. Pitcher trap had lower
net photosynthetic rate (P
N) in comparison to noncarnivorous lamina, whereas the rate of respiration (R
D) was not significantly different. This was in accordance with lower stomatal density and Chl concentration in the pitcher
trap. On the other hand maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of photochemical energy conversion in PSII (ΦPSII) was not significantly different. Nonphotochemical quenching (NPQ) was significantly higher in the lamina at higher irradiance.
These data are in accordance with hypothesis that changing the leaf shape in carnivorous plants to make it a better trap generally
makes it less efficient at photosynthesis. However, the pitcher of Cephalotus had much higher P
N than it was expected from the data set of the genus Nepenthes. Because it is not possible to optimize for contrasting function such as photosynthesis and carnivory, it is hypothesized
that Cephalotus pitchers are less elaborated for carnivorous function than the pitchers of Nepenthes. 相似文献
2.
Near-isogenic lines of maize varying in their genes for flavonoid biosynthesis were utilized to examine the effects of foliar
flavonoids and nutrient deficiency on maximum net photosynthetic rate (P
N) and chlorophyll (Chl) fluorescence (Fv/Fm) in response to ultraviolet-B (UV-B) radiation. Plants with deficient (30 to 70 % lower N, K, Mn, Fe, and Zn) and sufficient
nutrients were exposed to four irradiation regimes: (1) no UV-B with solar photosynthetically active radiation (PAR), (2) two day shift to ambient artificial UV-B, 8.2–9.5 kJ m−2 d−1 (21–25 mmol m−2 d−1); (3) continuous ambient artificial UV-B; (4) continuous solar UV-B in Hawaii 12–18 kJ m−2 d−1 (32–47 mmol m−2 d−1). The natural ratio of UVB: PAR (0.25–0.40) was maintained in the UV-B treatments. In the adequately fertilized plants, lines
b and lc had higher contents of flavonoids and anthocyanins than did lines hi27 and dta. UV-B induced the accumulation of
foliar flavonoids in lines hi27 and b, but not in the low flavonoid line dta or in the high flavonoid line lc. In plants grown
on deficient relative to adequate nutrients, flavonoid and anthocyanin contents decreased by 30–40 and 40–50 %, respectively,
and Chl a and Chl b contents decreased by 30 and 70 %, respectively. The UV-B treatments did not significantly affect P
N and Fv/Fm in plants grown on sufficient nutrients, except in the low flavonoid lines dta and hi27 in which P
N and Fv/Fm decreased by ∼15 %. P
N, Fv/Fm, and stomatal conductance decreased markedly (20–30 %) in all lines exposed to UV-B when grown on low nutrients. The decrease
in Fv/Fm was 10 % less in higher flavonoid lines b and lc. The photosynthetic apparatus of maize readily tolerated ambient UV-B in
the tropics when plants were adequately fertilized. In contrast, ambient UV-B combined with nutrient deficiency significantly
reduced photosynthesis in this C4 plant. Nutrient deficiency increased the susceptibility of maize to UV-B-induced photoinhibition in part by decreasing the
contents of photoprotective compounds. 相似文献
3.
Background and Aims
Cost–benefit models predict that carnivory can increase the rate of photosynthesis (AN) by leaves of carnivorous plants as a result of increased nitrogen absorption from prey. However, the cost of carnivory includes decreased AN and increased respiration rates (RD) of trapping organs. The principal aim of the present study was to assess the costs and benefits of carnivory in the pitcher plant Nepenthes talangensis, leaves of which are composed of a lamina and a pitcher trap, in response to feeding with beetle larvae.Methods
Pitchers of Nepenthes grown at 200 µmol m−2 s−1 photosynthetically active radiation (PAR) were fed with insect larvae for 2 months, and the effects on the photosynthetic processes were then assessed by simultaneous measurements of gas exchange and chlorophyll fluorescence of laminae and pitchers, which were correlated with nitrogen, carbon and total chlorophyll concentrations.Key Results
AN and maximum (Fv/Fm) and effective quantum yield of photosystem II (ΦPSII) were greater in the fed than unfed laminae but not in the fed compared with unfed pitchers. Respiration rate was not significantly affected in fed compared with unfed plants. The unfed plants had greater non-photochemical quenching (NPQ) of chlorophyll fluorescence. Higher NPQ in unfed lamina did not compensate for their lower ΦPSII, resulting in lower photochemical quenching (QP) and thus higher excitation pressure on PSII. Biomass and nitrogen and chlorophyll concentration also increased as a result of feeding. The cost of carnivory was shown by lower AN and ΦPSII in pitchers than in laminae, but RD depended on whether it was expressed on a dry weight or a surface area basis. Correlation between nitrogen and AN in the pitchers was not found. Cost–benefit analysis showed a large beneficial effect on photosynthesis from feeding as light intensity increased from 200 to 1000 µmol m−2 s−1 PAR after which it did not increase further. All fed plants began to flower.Conclusion
Feeding pitchers with insect larvae increases AN of leaf laminae, due to higher nutrient acquisition, with strong correlation with nitrogen concentration, but AN of pitchers does not increase, despite increased nitrogen concentration in their tissue. Increased AN improves growth and reproduction and is likely to increase the competitive advantage of carnivorous over non-carnivorous plants in nutrient-poor habitats.Key words: carnivorous plants, chlorophyll fluorescence, Nepenthes talangensis, nitrogen, pitcher plant, photosynthetic rate, photosystem II, respiration rate 相似文献4.
This study investigated the nitrogen (N) acquisition from soil and insect capture during the growth of three species of pitcher
plants, Nepenthes mirabilis, Cephalotus follicularis and Darlingtonia californica. 15N/14N natural abundance ratios (δ15N) of plants and pitchers of different age, non-carnivorous reference plants, and insect prey were used to estimate proportional
contributions of insects to the N content of leaves and whole plants. Young Nepenthes leaves (phyllodes) carrying closed pitchers comprised major sinks for N and developed mainly from insect N captured elsewhere
on the plant. Their δ15N values of up to 7.2‰ were higher than the average δ15N value of captured insects (mean δ15N value = 5.3‰). In leaves carrying old pitchers that are acting as a N source, the δ15N decreased to 3.0‰ indicating either an increasing contribution of soil N to those plant parts which in fact captured the
insects or N gain from N2 fixation by microorganisms which may exist in old pitchers. The δ15N value of N in water collected from old pitchers was 1.2‰ and contained free amino acids. The fraction of insect N in young
and old pitchers and their associated leaves decreased from 1.0 to 0.3 mg g−1. This fraction decreased further with the size of the investigated tiller. Nepenthes contained on average 61.5 ± 7.6% (mean ± SD, range 50–71%) insect N based on the N content of a whole tiller. In the absence
of suitable non-carnivorous reference plants for Cephalotus, δ15N values were assessed across a developmental sequence from young plants lacking pitchers to large adults with up to 38 pitchers.
The data indicated dependence on soil N until 4 pitchers had opened. Beyond that stage, plant size increased with the number
of catching pitchers but the fraction of soil N remained high. Large Cephalotus plants were estimated to derive 26 ± 5.9% (mean ± SD of the three largest plants; range: 19–30%) of the N from insects. In
Cephalotus we observed an increased δ15N value in sink versus source pitchers of about 1.2‰ on average. Source and sink pitchers of Darlingtonia had a similar δ15N value, but plant N in this species showed δ15N signals closer to that of insect N than in either Cephalotus or Nepenthes. Insect N contributed 76.4 ± 8.4% (range 57–90%) to total pitcher N content. The data suggest complex patterns of partitioning
of insect and soil-derived N between source and sink regions in pitcher plants and possibly higher dependence on insect N
than recorded elsewhere for Drosera species.
Received: 14 April 1997 / Accepted: 18 August 1997 相似文献
5.
Photosynthesis, chlorophyll (Chl) a fluorescence, and nitrogen metabolism of hawthorn (Crataegus pinnatifida Bge.), subjected to exogenous L-glutamic acid (GLA) (200 mg l−1, 400 mg l−1, and 800 mg l−1) that possibly affect secondary metabolic regulation, were measured. The results indicated that photosynthetic and fluorescence
characteristics of hawthorn exhibited positive responses to the application of GLA. Different concentrations of GLA caused
an increase in Chl content, net photosynthetic rate (P
N) and stomatal conductance (g
s) as well as transpiration rate (E), and improved the carboxylation efficiency (CE), apparent quantum yield (AQY) and maximum carboxylation velocity of Rubisco
(Vcmax). Application of GLA could also enhance the maximum ratio of quantum yields of photochemical and concurrent non-photochemical
processes in PSII (Fv/F0), the maximal quantum yield of PSII (Fv/Fm), the probability that an absorbed photon will move an electron into the electron transport chain beyond QA (ΦEo) as well as the performance index on absorption basis (PIABS), but decreased the intercellular CO2 concentration (C
i) and the minimal fluorescence (F0). Application of GLA also induced an increase in nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2)
activities, and increased the soluble protein content, leaf nitrogen (N) content and N accumulation in leaves as well as the
plant biomass. However, the effects were different among different concentrations of GLA, and 800 mg l−1 GLA was better. This finding suggested that application of GLA is recommended to improve the photosynthetic capacity by increasing
the light energy conversion and CO2 transfer as well as the photochemical efficiency of PSII, and enhanced the nitrogen metabolism and growth and development
of plants. 相似文献
6.
Lubomír Adamec 《Central European Journal of Biology》2010,5(1):121-124
In this study, O2-based dark respiration rate (RD) in leaf and trap cuttings was compared in 9 terrestrial carnivorous plant species of 5 genera to decide whether traps represent
a greater energetic (maintanence) cost than leaves or photosynthetic parts of traps. RD values of cut strips of traps or leaves of terrestrial carnivorous plants submerged in water ranged between 2.2 and 8.4 nmol
g−1 s−1 (per unit dry weight) in pitcher traps of the genera Sarracenia, Nepenthes, and Cephalotus, while between 7.2 and 25 nmol g−1
DW s−1 in fly-paper or snapping traps or leaves of Dionaea and Drosera. No clear relationship between RD values of traps (or pitcher walls) and leaves (or pitcher wings or petioles) was found. However, RD values of separated Drosera prolifera tentacles exceeded those of leaf lamina 7.3 times. 相似文献
7.
Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400–700 nm): low, LI 60 μmol m−2 s−1; middle, MI 180 μmol m−2 s−1; and high, HI 270 μmol m−2 s−1]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants.
Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (FV/FM) and actual (ΦPS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic
oxygen evolution rate (P
N) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase.
P
N reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves
and changed their typical ontogenetic course. 相似文献
8.
Due to anthropogenic influences, solar UV-B irradiance at the earth’s surface is increasing. To determine the effects of enhanced
UV-B radiation on photosynthetic characteristics of Prunus dulcis, two-year-old seedlings of the species were submitted to four levels of UV-B stress, namely 0 (UV-Bc), 4.42 (UV-B1), 7.32 (UV-B2) and 9.36 (UV-B3) kJ m−2 d−1. Effects of UV-B stress on a range of chlorophyll (Chl) fluorescence parameters (FPs), Chl contents and photosynthetic gas-exchange
parameters were investigated. UV-B stress promoted an increase in minimal fluorescence of dark-adapted state (F0) and F0/Fm, and a decrease in variable fluorescence (Fv, Fv/Fm, Fv/F0 and F0/Fm) due to its adverse effects on photosystem II (PSII) activity. No significant change was observed for maximal fluorescence
of dark-adapted state (Fm). Enhanced UV-B radiation caused a significant inhibition of net photosynthetic rate (P
N) at UV-B2 and UV-B3 levels and this was accompanied by a reduction in stomatal conductance (g
s) and transpiration rate (E). The contents of Chl a, b, and total Chl content (a+b) were also significantly reduced at increased UV-B stress. In general, adverse UV-B effects became significant at the highest
tested radiation dose 9.36 kJ m−2 d−1. The most sensitive indicators for UV-B stress were Fv/F0, Chl a content and P
N. Significant P<0.05 alteration in these parameters was found indicating the drastic effect of UV-B radiation on P. dulcis. 相似文献
9.
Abies faxoniana is a key species in reforestation processes in the southeast of the Qinghai-Tibetan Plateau of China. The changes in growth,
photosynthesis and nutrient status of A. faxoniana seedlings exposed to enhanced ultraviolet-B (UV-B), nitrogen supply and their combination were investigated. The experimental
design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m−2 day−1; enhanced UV-B, 14.33 KJ m−2 day−1) and two nitrogen levels (0; 20 g N m−2). The results indicated that: (1) enhanced UV-B significantly caused a marked decline in growth parameters, net photosynthetic
rate (Pn), photosynthetic pigments and F
v/F
m, (2) supplemental nitrogen supply increased the accumulation of total biomass, Pn, photosynthetic pigments and F
v/F
m under ambient UV-B, whereas supplemental nitrogen supply reduced Pn, and not affect biomass under enhanced UV-B, (3) enhanced
UV-B or nitrogen supply changed the concentration of nutrient elements of various organs. 相似文献
10.
Effects of zinc (12–180 μM) alone and in mixtures with 12 μM Cd on metal accumulation, dry masses of roots and shoots, root
respiration rate, variable to maximum fluorescence ratio (FV/FM), and content of photosynthetic pigments were studied in hydroponically cultivated chamomile (Matricaria recutita) plants. The content of Zn in roots and shoots increased with the increasing external Zn concentration and its accumulation
in the roots was higher than that in the shoots. While at lower Zn concentrations (12 and 60 μM) the presence of 12 μM Cd
decreased Zn accumulation in the roots, treatment with 120 and 180 μM Zn together with 12 μM Cd caused enhancement of Zn content
in the root. Presence of Zn (12–120 μM) decreased Cd accumulation in roots. On the other hand, Cd content in the shoots of
plants treated with Zn + Cd exceeded that in the plants treated only with 12 μM Cd. Only higher Zn concentrations (120 and
180 μM) and Zn + Cd mixtures negatively influenced dry mass, chlorophyll (Chl) and carotenoid content, FV/FM and root respiration rate. Chl b was reduced to a higher extent than Chl a. 相似文献
11.
Leaf Gas Exchange and Chlorophyll Fluorescence Parameters in Phaseolus Vulgaris as Affected by Nitrogen and Phosphorus Deficiency 总被引:2,自引:0,他引:2
The effects of N and P deficiency, isolated or in combination, on leaf gas exchange and fast chlorophyll (Chl) fluorescence
emission were studied in common bean cv. Negrito. 10-d-old plants grown in aerated nutrient solution were supplied with high
N (HN, 7.5 mol m−3) or low N (LN, 0.5 mol m−3), and also with high P (HP, 0.5 mol m−3) or low P (LP, 0.005 mol m−3). Regardless of the external P supply, in LN plants the initial fluorescence (F0) increased 12 % in parallel to a quenching of about 14 % in maximum fluorescence (Fm). As a consequence, the variable to maximum fluorescence ratio (Fv/Fm) decreased by about 7 %, and the variable to initial fluorescence ratio (Fv/F0) was lowered by 25 % in relation to control plants. In LP plants, Fv/Fm remained unchanged whilst Fv/F0 decreased slightly as a result of 5 % decline in Fm. Under N deficiency, the net photosynthetic rate (P
N) halved at 6 d after imposition of treatment and so remained afterwards. As compared to LN plants, P
N declined in LP plants latter and to a less extent. From 12 d of P deprivation onwards. P
N fell down progressively to display rates similar to those of LN plants only at the end of the experiment. The greater P
N in LP plants was not reflected in larger biomass accumulation in relation to LN beans. In general, P and N limitation affected
photosynthesis parameters and growth without showing any synergistic or additive effect between deficiency of both nutrients.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
12.
Plant growth, chlorophyll (Chl) content, photosynthetic gas exchange, ribulose-1,5-bisphosphate carboxylase (RuBPCO) enzyme
activity, and Chl fluorescence in radish (Raphanus sativus var. longipinnatus) plants were examined after turnip mosaic virus (TuMV) infection. Plant fresh mass, dry mass, Chl content, net photosynthetic
rate (P
N), transpiration rate (E), stomatal conductance (g
s), and RuBPCO activity were significantly lower in infected plants after 5 weeks of virus infection as compared to healthy
plants. The 5-week virus infection did not induce significant differences in intercellular CO2 concentration (C
i, photochemical efficiency of photosystem 2, PS2 (Fv/Fm), excitation capture efficiency of open PS2 reaction centres (Fv'/Fm'), effective quantum efficiency of photosystem 2 (ΔF/Fm'), and photochemical quenching (qP), but non-photochemical quenching (qN) and alternative electron sink (AES) were significantly enhanced. Thus the decreased plant biomass of TuMV-infected plants
might be associated with the decreased photosynthetic activity mainly due to reduced RuBPCO activity. 相似文献
13.
Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes
in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance,
SI (1 700 μmol m−2 s−1). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation.
During HI (0–3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (Fv/Fm), quantum efficiency of PS2 electron transport (ΦPS2), photochemical quenching (qP), as well as rate of photochemistry (Prate), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (Drate) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78–83 % conversion of violaxanthin into antheraxanthin
and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55–0.73) and high
1–qP (0.57–0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic
apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m−2 s−1) and high, HI (700 μmol m−2 s−1) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under
LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI.
Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to
HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size. 相似文献
14.
Plasma-membrane H+-ATPases are expressed in pitchers of the carnivorous plant Nepenthes alata Blanco
Nepenthes is a unique genus of carnivorous plants that can capture insects in trapping organs called pitchers and digest them in pitcher
fluid. The pitcher fluid includes digestive enzymes and is strongly acidic. We found that the fluid pH decreased when prey
accumulates in the pitcher fluid of Nepenthes alata. The pH decrease may be important for prey digestion and the absorption of prey-derived nutrients. To identify the proton
pump involved in the acidification of pitcher fluid, plant proton-pump homologs were cloned and their expressions were examined.
In the lower part of pitchers with natural prey, expression of one putative plasma-membrane (PM) H+-ATPase gene, NaPHA3, was considerably higher than that of the putative vacuolar H+-ATPase (subunit A) gene, NaVHA1, or the putative vacuolar H+-pyrophosphatase gene, NaVHP1. Expression of one PM H+-ATPase gene, NaPHA1, was detected in the head cells of digestive glands in the lower part of pitchers, where proton extrusion may occur. Involvement
of the PM H+-ATPase in the acidification of pitcher fluid was also supported by experiments with proton-pump modulators; vanadate inhibited
proton extrusion from the inner surface of pitchers, whereas bafilomycin A1 did not, and fusicoccin induced proton extrusion. These results strongly suggest that the PM H+-ATPase is responsible for acidification of the pitcher fluid of Nepenthes.
Received: 8 June 2000 / Accepted: 8 August 2000 相似文献
15.
The use of Jatropha curcas oil as a source of biofuel has been well-explored. However, the physiological and growth studies of J. curcas have received considerably lesser attention. In this study, leaf gas exchange measurements and leaf nitrogen content were
determined for four varieties of J. curcas, grown in the field or in pots. Based on stable carbon isotope analysis (δ13C) and gas-exchange studies, J. curcas is a C3 sun plant and the range of leaf photosynthetic rates (or CO2 assimilation rates, P
Nmax) were typically between 7 and 25 μmol(CO2) m−2 s−1 and light saturation generally occurred beyond 800 μmol(quanta) m−2 s−1. Higher rates of leaf photosynthesis were generally obtained with the mature leaves. In addition, increased foliar P
Nmax were recorded in potted J. curcas variety Indiana with increasing nitrogen (N) nutrition levels. These plants also showed greater growth, increased leaf N
content, higher maximum CO2 assimilation capacity (P
NhighCO2) and chlorophyll (Chl) content, indicating the potential of optimizing the growth of Jatropha by varying fertilizer nutrient levels. A rapid assessment for leaf N using a nondestructive and portable Chl meter had been
established for J. curcas. This approach will allow repeated sampling of the same plant over time and thus enable the monitoring of the appropriate
levels of soil fertility to achieve good Jatropha plantation productivity. High N nutrition improved the overall plant oil yield by increasing the total number of fruits/seeds
produced per plant, while not affecting the intrinsic seed oil content. 相似文献
16.
Maize (Zea mays L.) seedlings were grown in nutrient solution culture containing 0, 5, and 20 μM cadmium (Cd) and the effects on various
aspects of photosynthesis were investigated after 24, 48, 96 and 168 h of Cd treatments. Photosynthetic rate (P
N) decreased after 48 h of 20 μM Cd and 96 h of 5μM Cd addition, respectively. Chl a and total Chl content in leaves declined under 48 h of Cd exposure. Chl b content decreased on extending the period of Cd exposure to 96 h. The maximum quantum efficiency and potential photosynthetic
capacity of PSII, indicated by Fv/Fm and Fv/Fo, respectively, were depressed after 96 h onset of Cd exposure. After 48 h of 5μM Cd and 24 h of 20 μM Cd treatments, the
activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.39) and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) in the leaves started to decrease, respectively. We found that the limitation of
photosynthetic capacity in Cd stressed maize leaves was associated with Cd toxicity on the light and the dark stages. However,
Cd stress initially reduced the activities of Rubisco and PEPC and subsequently affected the PSII electron transfer, suggesting
that the Calvin cycle reactions in maize plants are the primary target of the Cd toxic effect rather than PSII. 相似文献
17.
The response of barley (Hordeum vulgare L. cv. Akcent) to various photosynthetic photon flux densities (PPFDs) and elevated [CO2] [700 μmol (CO2) mol−1; EC] was studied by gas exchange, chlorophyll (Chl) a fluorescence, and pigment analysis. In comparison with barley grown under ambient [CO2] [350 μmol (CO2) mol−1; AC] the EC acclimation resulted in a decrease in photosynthetic capacity, reduced stomatal conductance, and decreased total
Chl content. The extent of acclimation depression of photosynthesis, the most pronounced for the plants grown at 730 μmol
m−2 s−1 (PPFD730), may be related to the degree of sink-limitation. The increased non-radiative dissipation of absorbed photon energy for
all EC plants corresponded to the higher de-epoxidation state of xanthophylls only for PPFD730 barley. Further, a pronounced decrease in photosystem 2 (PS2) photochemical efficiency (given as FV/FM) for EC plants grown at 730 and 1 200 μmol m−2 s−1 in comparison with AC barley was related to the reduced epoxidation of antheraxanthin and zeaxanthin back to violaxanthin
in darkness. Thus the EC conditions sensitise the photosynthetic apparatus of high-irradiance acclimated barley plants (particularly
PPFD730) to the photoinactivation of PS2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Photosynthetic rates of green leaves (GL) and green flower petals (GFP) of the CAM plant Dendrobium cv. Burana Jade and their sensitivities to different growth irradiances were studied in shade-grown plants over a period
of 4 weeks. Maximal photosynthetic O2 evolution rates and CAM acidities [dawn/dusk fluctuations in titratable acidity] were higher in leaves exposed to intermediate
sunlight [a maximal photosynthetic photon flux density (PPFD) of 500–600 μmol m−2 s−1] than in leaves grown under full sunlight (a maximal PPFD of 1 000–1 200 μmol m−2 s−1) and shade (a maximal PPFD of 200–250 μmol m−2 s−1). However, these two parameters of GFP were highest in plants grown under the shade and lowest in full sun-grown plants.
Both GL and GFP of plants exposed to full sunlight had lower predawn Fv/Fm [dark adapted ratio of variable to maximal fluorescence (the maximal photosystem 2 yield without actinic irradiation)] than
those of shade-grown plants. When exposed to intermediate sunlight, however, there were no significant changes in predawn
Fv/Fm in GL whereas a significant decrease in predawn Fv/Fm was found in GFP of the same plant. GFP exposed to full sunlight exhibited a greater decrease in predawn Fv/Fm compared to those exposed to intermediate sunlight. The patterns of changes in total chlorophyll (Chl) content of GL and
GFP were similar to those of Fv/Fm. Although midday Fv/Fm fluctuated with prevailing irradiance, changes of midday Fv/Fm after exposure to different growth irradiances were similar to those of predawn Fv/Fm in both GL and GFP. The decreases in predawn and midday Fv/Fm were much more pronounced in GFP than in GL under full sunlight, indicating greater sensitivity in GFP to high irradiance
(HI). In the laboratory, electron transport rate and photochemical and non-photochemical quenching of Chl fluorescence were
also determined under different irradiances. All results indicated that GFP are more susceptible to HI than GL. Although the
GFP of Dendrobium cv. Burana Jade require a lower amount of radiant energy for photosynthesis and this plant is usually grown in the shade,
is not necessarily a shade plant. 相似文献
19.
Winter wheat is a grass species widely planted in northern and central China, where the increase of aerosols, air pollutants
and population density are causing significant reduction in solar irradiance. In order to investigate the adaptation of winter
wheat (Triticum aestivum L., cv. Yangmai 13) to low irradiance conditions occurring in the downstream plain of the Yangtze River (China), plants were
subjected to four solar irradiance treatments (100%, 60%, 40%, and 20% of environmental incident solar irradiance). Significant
increases in chlorophyll (Chl) and xanthophyll (Xan) pigments, and decreases in Chl a/b and Xan/Chl ratios were observed in plants under low light. Light-response curves showed higher net photosynthetic rates
(P
N) in fully irradiated plants, that also showed a higher light-compensation point. Shaded plants maintained high values of
minimal fluorescence of dark-adapted state (Fo) and maximum quantum efficiency of PSII photochemistry (Fv/Fm) that assess a lower degree of photoinhibition under low light. Reduced irradiance caused decreases in effective quantum
yield of PSII photochemistry (ΦPSII), electron transport rate (ETR), and nonphotochemical quenching coefficient (qN), and the promotion of excitation pressure of PSII (1 − qP). The activities of the antioxidant enzymes superoxide dismutase and peroxidase were high under reduced light whereas no
light-dependent changes in catalase activity were observed. Thiobarbituric acid reactive species content and electrolyte leakage
decreased under shaded plants that showed a lower photooxidative damage. The results suggest that winter wheat cv. Yangmai
13 is able to maintain a high photosynthetic efficiency under reduced solar irradiance and acclimates well to shading tolerance.
The photosynthetic and antioxidant responses of winter wheat to low light levels could be important for winter wheat cultivation
and productivity. 相似文献
20.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against
damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F
V/F
M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/F′M) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes
(F
0/F
M), the degree of reaction center closure (1 − q
p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae
(1 − F′V/F′M). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight,
and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective
effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/F′M and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth
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